[tz] [PROPOSED] Merge timezones that are alike since 1970

Magnus Fromreide magfr at lysator.liu.se
Tue Jun 1 09:29:34 UTC 2021


On Thu, May 20, 2021 at 10:57:48AM -0700, Paul Eggert via tz wrote:
> On 5/10/21 1:38 AM, Paul Eggert wrote:
> > I'd like to do more tests before installing it into the development tzdb
> > repository on GitHub. Also, the patch needs a proper NEWS entry and
> > commit message before installing.
> 
> I did that and installed the attached revised patch into the development
> repository.
> 
> The second attachment 'adjustments.diff' attempts to records adjustments to
> this patch, compared to the patch I circulated ten days ago.
> 'adjustments.diff' is hand-edited due to merges and so is intended only for
> human consumption.
> 
> The most significant adjustment was to add Link lines to 'backzone' so that
> people interested in out-of-scope pre-1970 data won't see any changes due to
> this patch. There are also some adjustments to commentary and a dependency
> fix in the Makefile.

The EU timezones are up for changes any year now - they have this stop
observing DST that is decided but was postponed to 2021 before the
pandemic struck so we will see when it actually happens.

/MF

> From 1edbb16e933a6ba6dceefd2bd7057b5ce00dd13c Mon Sep 17 00:00:00 2001
> From: Paul Eggert <eggert at cs.ucla.edu>
> Date: Wed, 19 May 2021 19:09:40 -0700
> Subject: [PROPOSED] Merge timezones that are alike since 1970
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
> 
> * NEWS: Describe the change and its motivation.
> * Makefile (TZS_DEPS, check_tables): Depend on YDATA, not just
> PRIMARY_YDATA, since etcetera matters here.
> * africa (Africa/Abidjan, Ghana, Africa/Accra, Indian/Reunion)
> (Indian/Mahe):
> * antarctica (Indian/Kerguelen, Antarctica/DumontDUrville)
> (Antarctica/Syowa, Antarctica/Vostok):
> * asia (Asia/Brunei, Asia/Urumqi, NBorneo, Asia/Kuala_Lumpur)
> (Asia/Kuching, Indian/Maldives, Asia/Riyadh, Asia/Bangkok)
> (Asia/Dubai):
> * australasia (Indian/Christmas, Indian/Cocos, Pacific/Gambier)
> (Pacific/Tahiti, Pacific/Tarawa, Pacific/Majuro, Pacific/Chuuk)
> (Pacific/Pohnpei, Pacific/Palau, Pacific/Port_Moresby)
> (Pacific/Guadalcanal, Pacific/Funafuti, Pacific/Wake)
> (Pacific/Wallis):
> * europe (Denmark, Europe/Copenhagen, Iceland, Atlantic/Reykjavik)
> (Lux, Europe/Luxembourg, Europe/Monaco, Neth, Europe/Amsterdam)
> (Norway, Europe/Oslo, Europe/Stockholm):
> * northamerica (America/Blanc-Sablon, America/Atikokan)
> (America/Creston, Bahamas, America/Nassau):
> * southamerica (America/La_Paz, America/Curacao, America/Cayenne)
> (Atlantic/South_Georgia, America/Port_of_Spain):
> Move these duplicate Zone entries to 'backzone', and add
> backward-compatibility links in 'backward'.
> * checktab.awk: Don’t worry about links to Etc/*.
> * theory.html: Change examples to avoid merged-away zones.  Remove
> references to SET, and to Amsterdam, Bangkok, Copenhagen and Port
> Moresby Mean Times.
> * zone.tab, zone1970.tab: Change 3rd column to avoid links in
> 'backward', which might not be present.
> * zone1970.tab: Merge lines to match the above changes.
> ---
>  Makefile     |    6 +-
>  NEWS         |   17 +
>  africa       |  146 +-------
>  antarctica   |   59 +--
>  asia         |  170 +--------
>  australasia  |  101 +----
>  backward     |  129 +++++--
>  backzone     | 1011 +++++++++++++++++++++++++++++++++++++++++++++++++-
>  checktab.awk |    4 +-
>  etcetera     |    2 +
>  europe       |  313 +---------------
>  northamerica |  191 +---------
>  southamerica |   48 +--
>  theory.html  |   29 +-
>  zone.tab     |  156 ++++----
>  zone1970.tab |   80 ++--
>  16 files changed, 1314 insertions(+), 1148 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index d05f828..ce018ec 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -529,7 +529,7 @@ TZS_YEAR=	2050
>  TZS_CUTOFF_FLAG=	-c $(TZS_YEAR)
>  TZS=		to$(TZS_YEAR).tzs
>  TZS_NEW=	to$(TZS_YEAR)new.tzs
> -TZS_DEPS=	$(PRIMARY_YDATA) asctime.c localtime.c \
> +TZS_DEPS=	$(YDATA) asctime.c localtime.c \
>  			private.h tzfile.h zdump.c zic.c
>  # EIGHT_YARDS is just a yard short of the whole ENCHILADA.
>  EIGHT_YARDS = $(COMMON) $(DOCS) $(SOURCES) $(DATA) $(MISC) tzdata.zi
> @@ -802,9 +802,9 @@ check_links:	checklinks.awk $(TDATA_TO_CHECK) tzdata.zi
>  		$(AWK) -f checklinks.awk tzdata.zi
>  		touch $@
>  
> -check_tables:	checktab.awk $(PRIMARY_YDATA) $(ZONETABLES)
> +check_tables:	checktab.awk $(YDATA) $(ZONETABLES)
>  		for tab in $(ZONETABLES); do \
> -		  $(AWK) -f checktab.awk -v zone_table=$$tab $(PRIMARY_YDATA) \
> +		  $(AWK) -f checktab.awk -v zone_table=$$tab $(YDATA) \
>  		    || exit; \
>  		done
>  		touch $@
> diff --git a/NEWS b/NEWS
> index 6d1cd09..435a40f 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -26,6 +26,23 @@ Unreleased, experimental changes
>      (Thanks to P Chan, Michael Deckers, Alexander Krivenyshev and
>      Alois Treindl.)
>  
> +    Merge timezones whose timestamps agree since 1970, since pre-1970
> +    timestamps are out of scope.  This change does not affect
> +    post-1970 timestamps, and timezone historians who build with 'make
> +    PACKRATDATA=backzone' should see no changes to pre-1970 timestamps.
> +    When merging, keep the most-populous location's data, and move
> +    data for other locations to 'backzone' with a backward
> +    compatibility link in 'backward'.  Also, merge timezones with
> +    neither post-1970 clock changes nor alphabetic abbreviations into
> +    their Etc counterparts.  For example, move the Europe/Oslo data to
> +    'backzone' with a link in 'backward' from Europe/Berlin because
> +    the two timezones' timestamps agree since 1970; this change
> +    affects some pre-1966 timestamps in Europe/Oslo because Berlin and
> +    Oslo disagreed before 1966.  For another example, move the
> +    Asia/Aden data to 'backzone' with a link in 'backward' from
> +    Etc/GMT-3.  Affected entries range from Africa/Abidjan to
> +    Pacific/Yap.
> +
>    Changes to maintenance procedure
>  
>      The new file SECURITY covers how to report security-related bugs.
> diff --git a/africa b/africa
> index a867cc4..d842502 100644
> --- a/africa
> +++ b/africa
> @@ -105,7 +105,7 @@ Zone	Africa/Algiers	0:12:12 -	LMT	1891 Mar 16
>  # See Africa/Maputo.
>  
>  # Burkina Faso
> -# See Africa/Abidjan.
> +# See Etc/GMT.
>  
>  # Burundi
>  # See Africa/Maputo.
> @@ -147,9 +147,7 @@ Zone	Africa/Ndjamena	1:00:12 -	LMT	1912        # N'Djamena
>  # See Africa/Lagos.
>  
>  # Côte d'Ivoire / Ivory Coast
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Africa/Abidjan	-0:16:08 -	LMT	1912
> -			 0:00	-	GMT
> +# See Etc/GMT.
>  
>  # Djibouti
>  # See Africa/Nairobi.
> @@ -370,94 +368,9 @@ Zone	Africa/Cairo	2:05:09 -	LMT	1900 Oct
>  # See Africa/Lagos.
>  
>  # The Gambia
> -# See Africa/Abidjan.
> -
>  # Ghana
> -
> -# From P Chan (2020-11-20):
> -# Interpretation Amendment Ordinance, 1915 (No.24 of 1915) [1915-11-02]
> -# Ordinances of the Gold Coast, Ashanti, Northern Territories 1915, p 69-71
> -# https://books.google.com/books?id=ErA-AQAAIAAJ&pg=PA70
> -# This Ordinance added "'Time' shall mean Greenwich Mean Time" to the
> -# Interpretation Ordinance, 1876.
> -#
> -# Determination of the Time Ordinance, 1919 (No. 18 of 1919) [1919-11-24]
> -# Ordinances of the Gold Coast, Ashanti, Northern Territories 1919, p 75-76
> -# https://books.google.com/books?id=MbA-AQAAIAAJ&pg=PA75
> -# This Ordinance removed the previous definition of time and introduced DST.
> -#
> -# Time Determination Ordinance (Cap. 214)
> -# The Laws of the Gold Coast (including Togoland Under British Mandate)
> -# Vol. II (1937), p 2328
> -# https://books.google.com/books?id=Z7M-AQAAIAAJ&pg=PA2328
> -# Revised edition of the 1919 Ordinance.
> -#
> -# Time Determination (Amendment) Ordinance, 1940 (No. 9 of 1940) [1940-04-06]
> -# Annual Volume of the Laws of the Gold Coast:
> -# Containing All Legislation Enacted During Year 1940, p 22
> -# https://books.google.com/books?id=1ao-AQAAIAAJ&pg=PA22
> -# This Ordinance changed the forward transition from September to May.
> -#
> -# Defence (Time Determination Ordinance Amendment) Regulations, 1942
> -# (Regulations No. 6 of 1942) [1942-01-31, commenced on 1942-02-08]
> -# Annual Volume of the Laws of the Gold Coast:
> -# Containing All Legislation Enacted During Year 1942, p 48
> -# https://books.google.com/books?id=Das-AQAAIAAJ&pg=PA48
> -# These regulations advanced the [standard] time by thirty minutes.
> -#
> -# Defence (Time Determination Ordinance Amendment (No.2)) Regulations,
> -# 1942 (Regulations No. 28 of 1942) [1942-04-25]
> -# Annual Volume of the Laws of the Gold Coast:
> -# Containing All Legislation Enacted During Year 1942, p 87
> -# https://books.google.com/books?id=Das-AQAAIAAJ&pg=PA87
> -# These regulations abolished DST and changed the time to GMT+0:30.
> -#
> -# Defence (Revocation) (No.4) Regulations, 1945 (Regulations No. 45 of
> -# 1945) [1945-10-24, commenced on 1946-01-06]
> -# Annual Volume of the Laws of the Gold Coast:
> -# Containing All Legislation Enacted During Year 1945, p 256
> -# https://books.google.com/books?id=9as-AQAAIAAJ&pg=PA256
> -# These regulations revoked the previous two sets of Regulations.
> -#
> -# Time Determination (Amendment) Ordinance, 1945 (No. 18 of 1945) [1946-01-06]
> -# Annual Volume of the Laws of the Gold Coast:
> -# Containing All Legislation Enacted During Year 1945, p 69
> -# https://books.google.com/books?id=9as-AQAAIAAJ&pg=PA69
> -# This Ordinance abolished DST.
> -#
> -# Time Determination (Amendment) Ordinance, 1950 (No. 26 of 1950) [1950-07-22]
> -# Annual Volume of the Laws of the Gold Coast:
> -# Containing All Legislation Enacted During Year 1950, p 35
> -# https://books.google.com/books?id=e60-AQAAIAAJ&pg=PA35
> -# This Ordinance restored DST but with thirty minutes offset.
> -#
> -# Time Determination Ordinance (Cap. 264)
> -# The Laws of the Gold Coast, Vol. V (1954), p 380
> -# https://books.google.com/books?id=Mqc-AQAAIAAJ&pg=PA380
> -# Revised edition of the Time Determination Ordinance.
> -#
> -# Time Determination (Amendment) Ordinance, 1956 (No. 21 of 1956) [1956-08-29]
> -# Annual Volume of the Ordinances of the Gold Coast Enacted During the
> -# Year 1956, p 83
> -# https://books.google.com/books?id=VLE-AQAAIAAJ&pg=PA83
> -# This Ordinance abolished DST.
> -
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
> -Rule	Ghana	1919	only	-	Nov	24	0:00	0:20	+0020
> -Rule	Ghana	1920	1942	-	Jan	 1	2:00	0	GMT
> -Rule	Ghana	1920	1939	-	Sep	 1	2:00	0:20	+0020
> -Rule	Ghana	1940	1941	-	May	 1	2:00	0:20	+0020
> -Rule	Ghana	1950	1955	-	Sep	 1	2:00	0:30	+0030
> -Rule	Ghana	1951	1956	-	Jan	 1	2:00	0	GMT
> -
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Africa/Accra	-0:00:52 -	LMT	1915 Nov  2
> -			 0:00	Ghana	%s	1942 Feb  8
> -			 0:30	-	+0030	1946 Jan  6
> -			 0:00	Ghana	%s
> -
>  # Guinea
> -# See Africa/Abidjan.
> +# See Etc/GMT.
>  
>  # Guinea-Bissau
>  #
> @@ -612,7 +525,7 @@ Zone	Africa/Tripoli	0:52:44 -	LMT	1920
>  
>  # Mali
>  # Mauritania
> -# See Africa/Abidjan.
> +# See Etc/GMT.
>  
>  # Mauritius
>  
> @@ -711,7 +624,7 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
>  # See Africa/Nairobi.
>  
>  # Morocco
> -# See the 'europe' file for Spanish Morocco (Africa/Ceuta).
> +# See Africa/Ceuta for Spanish Morocco.
>  
>  # From Alex Krivenyshev (2008-05-09):
>  # Here is an article that Morocco plan to introduce Daylight Saving Time between
> @@ -1356,29 +1269,15 @@ Zone	Africa/Lagos	0:13:35 -	LMT	1905 Jul  1
>  			1:00	-	WAT
>  
>  # Réunion
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Indian/Reunion	3:41:52 -	LMT	1911 Jun # Saint-Denis
> -			4:00	-	+04
> +# See Etc/GMT-4.
>  #
>  # Crozet Islands also observes Réunion time; see the 'antarctica' file.
> -#
> -# Scattered Islands (Îles Éparses) administered from Réunion are as follows.
> -# The following information about them is taken from
> -# Îles Éparses (<http://www.outre-mer.gouv.fr/domtom/ile.htm>, 1997-07-22,
> -# in French; no longer available as of 1999-08-17).
> -# We have no info about their time zone histories.
> -#
> -# Bassas da India - uninhabited
> -# Europa Island - inhabited from 1905 to 1910 by two families
> -# Glorioso Is - inhabited until at least 1958
> -# Juan de Nova - uninhabited
> -# Tromelin - inhabited until at least 1958
>  
>  # Rwanda
>  # See Africa/Maputo.
>  
>  # St Helena
> -# See Africa/Abidjan.
> +# See Etc/GMT.
>  # The other parts of the St Helena territory are similar:
>  #	Tristan da Cunha: on GMT, say Whitman and the CIA
>  #	Ascension: on GMT, say the USNO (1995-12-21) and the CIA
> @@ -1413,34 +1312,13 @@ Zone	Africa/Sao_Tome	 0:26:56 -	LMT	1884
>  			 0:00	-	GMT
>  
>  # Senegal
> -# See Africa/Abidjan.
> +# See Etc/GMT.
>  
>  # Seychelles
> -
> -# From P Chan (2020-11-27):
> -# Standard Time was adopted on 1907-01-01.
> -#
> -# Standard Time Ordinance (Chapter 237)
> -# The Laws of Seychelles in Force on the 31st December, 1971, Vol. 6, p 571
> -# https://books.google.com/books?id=efE-AQAAIAAJ&pg=PA571
> -#
> -# From Tim Parenti (2020-12-05):
> -# A footnote on https://books.google.com/books?id=DYdDAQAAMAAJ&pg=PA1689
> -# confirms that Ordinance No. 9 of 1906 "was brought into force on the 1st
> -# January, 1907."
> -
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Indian/Mahe	3:41:48 -	LMT	1907 Jan  1 # Victoria
> -			4:00	-	+04
> -# From Paul Eggert (2001-05-30):
> -# Aldabra, Farquhar, and Desroches, originally dependencies of the
> -# Seychelles, were transferred to the British Indian Ocean Territory
> -# in 1965 and returned to Seychelles control in 1976.  We don't know
> -# whether this affected their time zone, so omit this for now.
> -# Possibly the islands were uninhabited.
> +# See Etc/GMT-4.
>  
>  # Sierra Leone
> -# See Africa/Abidjan.
> +# See Etc/GMT.
>  
>  # Somalia
>  # See Africa/Nairobi.
> @@ -1505,7 +1383,7 @@ Zone	Africa/Juba	2:06:28 -	LMT	1931
>  # See Africa/Nairobi.
>  
>  # Togo
> -# See Africa/Abidjan.
> +# See Etc/GMT.
>  
>  # Tunisia
>  
> @@ -1599,7 +1477,7 @@ Rule	Tunisia	2005	only	-	Sep	30	 1:00s	0	-
>  Rule	Tunisia	2006	2008	-	Mar	lastSun	 2:00s	1:00	S
>  Rule	Tunisia	2006	2008	-	Oct	lastSun	 2:00s	0	-
>  
> -# See Europe/Paris for PMT-related transitions.
> +# See Europe/Paris commentary for PMT-related transitions.
>  # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
>  Zone	Africa/Tunis	0:40:44 -	LMT	1881 May 12
>  			0:09:21	-	PMT	1911 Mar 11 # Paris Mean Time
> diff --git a/antarctica b/antarctica
> index ed750a8..6b100a7 100644
> --- a/antarctica
> +++ b/antarctica
> @@ -148,7 +148,7 @@ Zone Antarctica/Mawson	0	-	-00	1954 Feb 13
>  #
>  # Alfred Faure, Possession Island, Crozet Islands, -462551+0515152, since 1964;
>  #	sealing & whaling stations operated variously 1802/1911+;
> -#	see Indian/Reunion.
> +#	see Etc/GMT-4.
>  #
>  # Martin-de-Viviès, Amsterdam Island, -374105+0773155, since 1950
>  # Port-aux-Français, Kerguelen Islands, -492110+0701303, since 1951;
> @@ -157,22 +157,10 @@ Zone Antarctica/Mawson	0	-	-00	1954 Feb 13
>  # St Paul Island - near Amsterdam, uninhabited
>  #	fishing stations operated variously 1819/1931
>  #
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Indian/Kerguelen	0	-	-00	1950 # Port-aux-Français
> -			5:00	-	+05
> +# Kerguelen - see Etc/GMT-5.
>  #
>  # year-round base in the main continent
> -# Dumont d'Urville, Île des Pétrels, -6640+14001, since 1956-11
> -# <https://en.wikipedia.org/wiki/Dumont_d'Urville_Station> (2005-12-05)
> -#
> -# Another base at Port-Martin, 50km east, began operation in 1947.
> -# It was destroyed by fire on 1952-01-14.
> -#
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Antarctica/DumontDUrville 0 -	-00	1947
> -			10:00	-	+10	1952 Jan 14
> -			0	-	-00	1956 Nov
> -			10:00	-	+10
> +# Dumont d'Urville - see Etc/GMT-10.
>  
>  # France & Italy - year-round base
>  # Concordia, -750600+1232000, since 2005
> @@ -188,20 +176,7 @@ Zone Antarctica/DumontDUrville 0 -	-00	1947
>  # Zuchelli, Terra Nova Bay, -744140+1640647, since 1986
>  
>  # Japan - year-round bases
> -# Syowa (also known as Showa), -690022+0393524, since 1957
> -#
> -# From Hideyuki Suzuki (1999-02-06):
> -# In all Japanese stations, +0300 is used as the standard time.
> -#
> -# Syowa station, which is the first antarctic station of Japan,
> -# was established on 1957-01-29.  Since Syowa station is still the main
> -# station of Japan, it's appropriate for the principal location.
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Antarctica/Syowa	0	-	-00	1957 Jan 29
> -			3:00	-	+03
> -# See:
> -# NIPR Antarctic Research Activities (1999-08-17)
> -# http://www.nipr.ac.jp/english/ara01.html
> +# See Etc/GMT-3.
>  
>  # S Korea - year-round base
>  # Jang Bogo, Terra Nova Bay, -743700+1641205 since 2014
> @@ -265,31 +240,7 @@ Zone Antarctica/Troll	0	-	-00	2005 Feb 12
>  #	year-round from 1960/61 to 1992
>  
>  # Vostok, since 1957-12-16, temporarily closed 1994-02/1994-11
> -# From Craig Mundell (1994-12-15):
> -# http://quest.arc.nasa.gov/antarctica/QA/computers/Directions,Time,ZIP
> -# Vostok, which is one of the Russian stations, is set on the same
> -# time as Moscow, Russia.
> -#
> -# From Lee Hotz (2001-03-08):
> -# I queried the folks at Columbia who spent the summer at Vostok and this is
> -# what they had to say about time there:
> -# "in the US Camp (East Camp) we have been on New Zealand (McMurdo)
> -# time, which is 12 hours ahead of GMT. The Russian Station Vostok was
> -# 6 hours behind that (although only 2 miles away, i.e. 6 hours ahead
> -# of GMT). This is a time zone I think two hours east of Moscow. The
> -# natural time zone is in between the two: 8 hours ahead of GMT."
> -#
> -# From Paul Eggert (2001-05-04):
> -# This seems to be hopelessly confusing, so I asked Lee Hotz about it
> -# in person.  He said that some Antarctic locations set their local
> -# time so that noon is the warmest part of the day, and that this
> -# changes during the year and does not necessarily correspond to mean
> -# solar noon.  So the Vostok time might have been whatever the clocks
> -# happened to be during their visit.  So we still don't really know what time
> -# it is at Vostok.  But we'll guess +06.
> -#
> -Zone Antarctica/Vostok	0	-	-00	1957 Dec 16
> -			6:00	-	+06
> +# See Etc/GMT-6.
>  
>  # S Africa - year-round bases
>  # Marion Island, -4653+03752
> diff --git a/asia b/asia
> index e2f6446..f1c3d7d 100644
> --- a/asia
> +++ b/asia
> @@ -255,10 +255,7 @@ Zone	Indian/Chagos	4:49:40	-	LMT	1907
>  			6:00	-	+06
>  
>  # Brunei
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Asia/Brunei	7:39:40 -	LMT	1926 Mar # Bandar Seri Begawan
> -			7:30	-	+0730	1933
> -			8:00	-	+08
> +# See Etc/GMT-8.
>  
>  # Burma / Myanmar
>  
> @@ -278,7 +275,7 @@ Zone	Asia/Yangon	6:24:47 -	LMT	1880        # or Rangoon
>  			6:30	-	+0630
>  
>  # Cambodia
> -# See Asia/Bangkok.
> +# See Etc/GMT-7.
>  
>  
>  # China
> @@ -534,7 +531,7 @@ Rule	PRC	1987	1991	-	Apr	Sun>=11	 2:00	1:00	D
>  # In earlier versions of this file, China had many separate Zone entries, but
>  # this was based on what were apparently incorrect data in Shanks & Pottenger.
>  # This has now been simplified to the two entries Asia/Shanghai and
> -# Asia/Urumqi, with the others being links for backward compatibility.
> +# Etc/GMT-6, with the others being links for backward compatibility.
>  # Proposed in 1918 and theoretically in effect until 1949 (although in practice
>  # mainly observed in coastal areas), the five zones were:
>  #
> @@ -556,7 +553,7 @@ Rule	PRC	1987	1991	-	Apr	Sun>=11	 2:00	1:00	D
>  # Yangchun, Yangjiang, Yu'nan, and Yunfu.
>  #
>  # Xin-zang Time ("Xinjiang-Tibet Time") UT +06
> -# This region is now part of either Asia/Urumqi or Asia/Shanghai with
> +# This region is now part of either Etc/GMT-6 or Asia/Shanghai with
>  # current boundaries uncertain; times before 1970 for areas that
>  # disagree with Ürümqi or Shanghai are not recorded here.
>  # The Gansu counties Aksay, Anxi, Dunhuang, Subei; west Qinghai;
> @@ -609,68 +606,14 @@ Rule	PRC	1987	1991	-	Apr	Sun>=11	 2:00	1:00	D
>  # 2. Kashi...
>  # 3. Urumqi...
>  # 4. Kashgar...
> -# ...
> -# 5. It seems that Uyghurs in Ürümqi has been using Xinjiang since at least the
> -# 1960's. I know of one Han, now over 50, who grew up in the surrounding
> -# countryside and used Xinjiang time as a child.
> -#
> -# 6. Likewise for Kashgar and the rest of south Xinjiang I don't know of any
> -# start date for Xinjiang time.
> -#
> -# Without having access to local historical records, nor the ability to legally
> -# publish them, I would go with October 1, 1949, when Xinjiang became the Uyghur
> -# Autonomous Region under the PRC. (Before that Uyghurs, of course, would also
> -# not be using Beijing time, but some local time.)
> -
> -# From David Cochrane (2014-03-26):
> -# Just a confirmation that Ürümqi time was implemented in Ürümqi on 1 Feb 1986:
> -# https://content.time.com/time/magazine/article/0,9171,960684,00.html
> -
> -# From Luther Ma (2014-04-22):
> -# I have interviewed numerous people of various nationalities and from
> -# different localities in Xinjiang and can confirm the information in Guo's
> -# report regarding Xinjiang, as well as the Time article reference by David
> -# Cochrane.  Whether officially recognized or not (and both are officially
> -# recognized), two separate times have been in use in Xinjiang since at least
> -# the Cultural Revolution: Xinjiang Time (XJT), aka Ürümqi Time or local time;
> -# and Beijing Time.  There is no confusion in Xinjiang as to which name refers
> -# to which time. Both are widely used in the province, although in some
> -# population groups might be use one to the exclusion of the other.  The only
> -# problem is that computers and smart phones list Ürümqi (or Kashgar) as
> -# having the same time as Beijing.
> -
> -# From Paul Eggert (2014-06-30):
> -# In the early days of the PRC, Tibet was given its own time zone (UT +06)
> -# but this was withdrawn in 1959 and never reinstated; see Tubten Khétsun,
> -# Memories of life in Lhasa under Chinese Rule, Columbia U Press, ISBN
> -# 978-0231142861 (2008), translator's introduction by Matthew Akester, p x.
> -# As this is before our 1970 cutoff, Tibet doesn't need a separate zone.
> -#
> -# Xinjiang Time is well-documented as being officially recognized.  E.g., see
> -# "The Working-Calendar for The Xinjiang Uygur Autonomous Region Government"
> -# <http://www.sinkiang.gov.cn/service/ourworking/> (2014-04-22).
> -# Unfortunately, we have no good records of time in Xinjiang before 1986.
> -# During the 20th century parts of Xinjiang were ruled by the Qing dynasty,
> -# the Republic of China, various warlords, the First and Second East Turkestan
> -# Republics, the Soviet Union, the Kuomintang, and the People's Republic of
> -# China, and tracking down all these organizations' timekeeping rules would be
> -# quite a trick.  Approximate this lost history by a transition from LMT to
> -# UT +06 at the start of 1928, the year of accession of the warlord Jin Shuren,
> -# which happens to be the date given by Shanks & Pottenger (no doubt as a
> -# guess) as the transition from LMT.  Ignore the usage of +08 before
> -# 1986-02-01 under the theory that the transition date to +08 is unknown and
> -# that the sort of users who prefer Asia/Urumqi now typically ignored the
> -# +08 mandate back then.
>  
>  # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
>  # Beijing time, used throughout China; represented by Shanghai.
>  Zone	Asia/Shanghai	8:05:43	-	LMT	1901
>  			8:00	Shang	C%sT	1949 May 28
>  			8:00	PRC	C%sT
> -# Xinjiang time, used by many in western China; represented by Ürümqi / Ürümchi
> -# / Wulumuqi.  (Please use Asia/Shanghai if you prefer Beijing time.)
> -Zone	Asia/Urumqi	5:50:20	-	LMT	1928
> -			6:00	-	+06
> +# See Etc/GMT-6 for Xinjiang time, used by many in western China.
> +# (Please use Asia/Shanghai if you prefer Beijing time.)
>  
>  
>  # Hong Kong
> @@ -2693,10 +2636,10 @@ Zone	Asia/Pyongyang	8:23:00 -	LMT	1908 Apr  1
>  ###############################################################################
>  
>  # Kuwait
> -# See Asia/Riyadh.
> +# See Etc/GMT-3.
>  
>  # Laos
> -# See Asia/Bangkok.
> +# See Etc/GMT-7.
>  
>  
>  # Lebanon
> @@ -2730,39 +2673,12 @@ Zone	Asia/Beirut	2:22:00 -	LMT	1880
>  			2:00	Lebanon	EE%sT
>  
>  # Malaysia
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
> -Rule	NBorneo	1935	1941	-	Sep	14	0:00	0:20	-
> -Rule	NBorneo	1935	1941	-	Dec	14	0:00	0	-
> -#
> -# peninsular Malaysia
> -# taken from Mok Ly Yng (2003-10-30)
> -# http://www.math.nus.edu.sg/aslaksen/teaching/timezone.html
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Asia/Kuala_Lumpur	6:46:46 -	LMT	1901 Jan  1
> -			6:55:25	-	SMT	1905 Jun  1 # Singapore M.T.
> -			7:00	-	+07	1933 Jan  1
> -			7:00	0:20	+0720	1936 Jan  1
> -			7:20	-	+0720	1941 Sep  1
> -			7:30	-	+0730	1942 Feb 16
> -			9:00	-	+09	1945 Sep 12
> -			7:30	-	+0730	1982 Jan  1
> -			8:00	-	+08
> -# Sabah & Sarawak
> -# From Paul Eggert (2014-08-12):
> -# The data entries here are mostly from Shanks & Pottenger, but the 1942, 1945
> -# and 1982 transition dates are from Mok Ly Yng.
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Asia/Kuching	7:21:20	-	LMT	1926 Mar
> -			7:30	-	+0730	1933
> -			8:00 NBorneo  +08/+0820	1942 Feb 16
> -			9:00	-	+09	1945 Sep 12
> -			8:00	-	+08
> +# For peninsular Malaysia see Asia/Singapore.
> +# For Sabah & Sarawak see Etc/GMT-8.
>  
>  # Maldives
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Indian/Maldives	4:54:00 -	LMT	1880 # Malé
> -			4:54:00	-	MMT	1960 # Malé Mean Time
> -			5:00	-	+05
> +# See Etc/GMT-5.
> +
>  
>  # Mongolia
>  
> @@ -2926,7 +2842,7 @@ Zone	Asia/Kathmandu	5:41:16 -	LMT	1920
>  			5:45	-	+0545
>  
>  # Oman
> -# See Asia/Dubai.
> +# See Etc/GMT-4.
>  
>  # Pakistan
>  
> @@ -3523,54 +3439,11 @@ Zone	Asia/Qatar	3:26:08 -	LMT	1920     # Al Dawhah / Doha
>  			3:00	-	+03
>  
>  # Saudi Arabia
> -#
> -# From Paul Eggert (2018-08-29):
> -# Time in Saudi Arabia and other countries in the Arabian peninsula was not
> -# standardized until 1968 or so; we don't know exactly when, and possibly it
> -# has never been made official.  Richard P Hunt, in "Islam city yielding to
> -# modern times", New York Times (1961-04-09), p 20, wrote that only airlines
> -# observed standard time, and that people in Jeddah mostly observed quasi-solar
> -# time, doing so by setting their watches at sunrise to 6 o'clock (or to 12
> -# o'clock for "Arab" time).
> -#
> -# Timekeeping differed depending on who you were and which part of Saudi
> -# Arabia you were in.  In 1969, Elias Antar wrote that although a common
> -# practice had been to set one's watch to 12:00 (i.e., midnight) at sunset -
> -# which meant that the time on one side of a mountain could differ greatly from
> -# the time on the other side - many foreigners set their watches to 6pm
> -# instead, while airlines instead used UTC +03 (except in Dhahran, where they
> -# used UTC +04), Aramco used UTC +03 with DST, and the Trans-Arabian Pipe Line
> -# Company used Aramco time in eastern Saudi Arabia and airline time in western.
> -# (The American Military Aid Advisory Group used plain UTC.)  Antar writes,
> -# "A man named Higgins, so the story goes, used to run a local power
> -# station. One day, the whole thing became too much for Higgins and he
> -# assembled his staff and laid down the law. 'I've had enough of this,' he
> -# shrieked. 'It is now 12 o'clock Higgins Time, and from now on this station is
> -# going to run on Higgins Time.' And so, until last year, it did."  See:
> -# Antar E. Dinner at When? Saudi Aramco World, 1969 March/April. 2-3.
> -# http://archive.aramcoworld.com/issue/196902/dinner.at.when.htm
> -# Also see: Antar EN. Arabian flying is confusing.
> -# Port Angeles (WA) Evening News. 1965-03-10. page 3.
> -#
> -# The TZ database cannot represent quasi-solar time; airline time is the best
> -# we can do.  The 1946 foreign air news digest of the U.S. Civil Aeronautics
> -# Board (OCLC 42299995) reported that the "... Arabian Government, inaugurated
> -# a weekly Dhahran-Cairo service, via the Saudi Arabian cities of Riyadh and
> -# Jidda, on March 14, 1947".  Shanks & Pottenger guessed 1950; go with the
> -# earlier date.
> -#
> -# Shanks & Pottenger also state that until 1968-05-01 Saudi Arabia had two
> -# time zones; the other zone, at UT +04, was in the far eastern part of
> -# the country.  Presumably this is documenting airline time.  Ignore this,
> -# as it's before our 1970 cutoff.
> -#
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Asia/Riyadh	3:06:52 -	LMT	1947 Mar 14
> -			3:00	-	+03
> +# See Etc/GMT-3.
>  
>  # Singapore
>  # taken from Mok Ly Yng (2003-10-30)
> -# http://www.math.nus.edu.sg/aslaksen/teaching/timezone.html
> +# https://web.archive.org/web/20190822231045/http://www.math.nus.edu.sg/~mathelmr/teaching/timezone.html
>  # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
>  Zone	Asia/Singapore	6:55:25 -	LMT	1901 Jan  1
>  			6:55:25	-	SMT	1905 Jun  1 # Singapore M.T.
> @@ -3819,10 +3692,7 @@ Zone	Asia/Dushanbe	4:35:12 -	LMT	1924 May  2
>  			5:00	-	+05
>  
>  # Thailand
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Asia/Bangkok	6:42:04	-	LMT	1880
> -			6:42:04	-	BMT	1920 Apr # Bangkok Mean Time
> -			7:00	-	+07
> +# See Etc/GMT-7.
>  
>  # Turkmenistan
>  # From Shanks & Pottenger.
> @@ -3834,9 +3704,7 @@ Zone	Asia/Ashgabat	3:53:32 -	LMT	1924 May  2 # or Ashkhabad
>  			5:00	-	+05
>  
>  # United Arab Emirates
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Asia/Dubai	3:41:12 -	LMT	1920
> -			4:00	-	+04
> +# See Etc/GMT-4.
>  
>  # Uzbekistan
>  # Byalokoz 1919 says Uzbekistan was 4:27:53.
> @@ -3926,9 +3794,9 @@ Zone Asia/Ho_Chi_Minh	7:06:40 -	LMT	1906 Jul  1
>  # details are unknown and would likely be too voluminous for this database.
>  #
>  # For timestamps in north Vietnam back to 1970 (the tzdb cutoff),
> -# use Asia/Bangkok; see the VN entries in the file zone1970.tab.
> +# use Etc/GMT-7; see the VN entries in the file zone1970.tab.
>  # For timestamps before 1970, see Asia/Hanoi in the file 'backzone'.
>  
>  
>  # Yemen
> -# See Asia/Riyadh.
> +# See Etc/GMT-3.
> diff --git a/australasia b/australasia
> index 18dfd93..9d3cd2f 100644
> --- a/australasia
> +++ b/australasia
> @@ -252,16 +252,10 @@ Zone Antarctica/Macquarie 0	-	-00	1899 Nov
>  			10:00	AT	AE%sT
>  
>  # Christmas
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Indian/Christmas	7:02:52 -	LMT	1895 Feb
> -			7:00	-	+07
> +# See Etc/GMT-7.
>  
>  # Cocos (Keeling) Is
> -# These islands were ruled by the Ross family from about 1830 to 1978.
> -# We don't know when standard time was introduced; for now, we guess 1900.
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Indian/Cocos	6:27:40	-	LMT	1900
> -			6:30	-	+0630
> +# See Asia/Yangon.
>  
>  
>  # Fiji
> @@ -409,12 +403,9 @@ Zone	Pacific/Fiji	11:55:44 -	LMT	1915 Oct 26 # Suva
>  
>  # French Polynesia
>  # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Pacific/Gambier	 -8:59:48 -	LMT	1912 Oct # Rikitea
> -			 -9:00	-	-09
>  Zone	Pacific/Marquesas -9:18:00 -	LMT	1912 Oct
>  			 -9:30	-	-0930
> -Zone	Pacific/Tahiti	 -9:58:16 -	LMT	1912 Oct # Papeete
> -			-10:00	-	-10
> +# See Etc/GMT+9 for the Gambier Islands and Etc/GMT+10 for the Society Islands.
>  # Clipperton (near North America) is administered from French Polynesia;
>  # it is uninhabited.
>  
> @@ -460,9 +451,8 @@ Zone	Pacific/Guam	-14:21:00 -	LMT	1844 Dec 31
>  			10:00	-	ChST	# Chamorro Standard Time
>  
>  # Kiribati
> +# See Etc/GMT-12 for the Gilbert Islands.
>  # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Pacific/Tarawa	 11:32:04 -	LMT	1901 # Bairiki
> -			 12:00	-	+12
>  Zone Pacific/Enderbury	-11:24:20 -	LMT	1901
>  			-12:00	-	-12	1979 Oct
>  			-11:00	-	-11	1994 Dec 31
> @@ -476,15 +466,8 @@ Zone Pacific/Kiritimati	-10:29:20 -	LMT	1901
>  # See Pacific/Guam.
>  
>  # Marshall Is
> +# See Etc/GMT-12 for most locations.
>  # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Pacific/Majuro	 11:24:48 -	LMT	1901
> -			 11:00	-	+11	1914 Oct
> -			  9:00	-	+09	1919 Feb  1
> -			 11:00	-	+11	1937
> -			 10:00	-	+10	1941 Apr  1
> -			  9:00	-	+09	1944 Jan 30
> -			 11:00	-	+11	1969 Oct
> -			 12:00	-	+12
>  Zone Pacific/Kwajalein	 11:09:20 -	LMT	1901
>  			 11:00	-	+11	1937
>  			 10:00	-	+10	1941 Apr  1
> @@ -494,22 +477,9 @@ Zone Pacific/Kwajalein	 11:09:20 -	LMT	1901
>  			 12:00	-	+12
>  
>  # Micronesia
> +# For Chuuk and Yap see Etc/GMT-10.
> +# For Pohnpei see Etc/GMT-11.
>  # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Pacific/Chuuk	-13:52:52 -	LMT	1844 Dec 31
> -			 10:07:08 -	LMT	1901
> -			 10:00	-	+10	1914 Oct
> -			  9:00	-	+09	1919 Feb  1
> -			 10:00	-	+10	1941 Apr  1
> -			  9:00	-	+09	1945 Aug
> -			 10:00	-	+10
> -Zone Pacific/Pohnpei	-13:27:08 -	LMT	1844 Dec 31	# Kolonia
> -			 10:32:52 -	LMT	1901
> -			 11:00	-	+11	1914 Oct
> -			  9:00	-	+09	1919 Feb  1
> -			 11:00	-	+11	1937
> -			 10:00	-	+10	1941 Apr  1
> -			  9:00	-	+09	1945 Aug
> -			 11:00	-	+11
>  Zone Pacific/Kosrae	-13:08:04 -	LMT	1844 Dec 31
>  			 10:51:56 -	LMT	1901
>  			 11:00	-	+11	1914 Oct
> @@ -658,16 +628,10 @@ Zone	Pacific/Norfolk	11:11:52 -	LMT	1901 # Kingston
>  			11:00	AN	+11/+12
>  
>  # Palau (Belau)
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Pacific/Palau	-15:02:04 -	LMT	1844 Dec 31	# Koror
> -			  8:57:56 -	LMT	1901
> -			  9:00	-	+09
> +# See Etc/GMT-9.
>  
>  # Papua New Guinea
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Pacific/Port_Moresby 9:48:40 -	LMT	1880
> -			9:48:32	-	PMMT	1895 # Port Moresby Mean Time
> -			10:00	-	+10
> +# See Etc/GMT-10 for most locations.
>  #
>  # From Paul Eggert (2014-10-13):
>  # Base the Bougainville entry on the Arawa-Kieta region, which appears to have
> @@ -787,9 +751,8 @@ Zone Pacific/Apia	 12:33:04 -	LMT	1892 Jul  5
>  
>  # Solomon Is
>  # excludes Bougainville, for which see Papua New Guinea
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Pacific/Guadalcanal 10:39:48 -	LMT	1912 Oct # Honiara
> -			11:00	-	+11
> +# See Etc/GMT-11.
> +
>  
>  # Tokelau
>  #
> @@ -830,9 +793,7 @@ Zone Pacific/Tongatapu	12:19:12 -	LMT	1945 Sep 10
>  			13:00	Tonga	+13/+14
>  
>  # Tuvalu
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Pacific/Funafuti	11:56:52 -	LMT	1901
> -			12:00	-	+12
> +# See Etc/GMT-12.
>  
>  
>  # US minor outlying islands
> @@ -891,9 +852,7 @@ Zone Pacific/Funafuti	11:56:52 -	LMT	1901
>  # uninhabited since World War II; was probably like Pacific/Kiritimati
>  
>  # Wake
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Pacific/Wake	11:06:28 -	LMT	1901
> -			12:00	-	+12
> +# See Etc/GMT-12.
>  
>  
>  # Vanuatu
> @@ -932,9 +891,7 @@ Zone	Pacific/Efate	11:13:16 -	LMT	1912 Jan 13 # Vila
>  			11:00	Vanuatu	+11/+12
>  
>  # Wallis and Futuna
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Pacific/Wallis	12:15:20 -	LMT	1901
> -			12:00	-	+12
> +# See Etc/GMT-12.
>  
>  ###############################################################################
>  
> @@ -1834,13 +1791,6 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
>  # Like the Ladrones (see Guam commentary), assume the Spanish East Indies
>  # kept American time until the Philippines switched at the end of 1844.
>  
> -# Alan Eugene Davis writes (1996-03-16),
> -# "I am certain, having lived there for the past decade, that 'Truk'
> -# (now properly known as Chuuk) ... is in the time zone GMT+10."
> -#
> -# Shanks & Pottenger write that Truk switched from UT +10 to +11
> -# on 1978-10-01; ignore this for now.
> -
>  # From Paul Eggert (1999-10-29):
>  # The Federated States of Micronesia Visitors Board writes in
>  # The Federated States of Micronesia - Visitor Information (1999-01-26)
> @@ -2001,9 +1951,6 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
>  # From Michael Deckers (2019-08-14):
>  # https://www.legislation.gov.au/Details/F2019C00010
>  
> -# Palau
> -# See commentary for Micronesia.
> -
>  # Pitcairn
>  
>  # From Rives McDow (1999-11-08):
> @@ -2173,26 +2120,6 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
>  # For now, guess that DST is discontinued.  That's what the IATA is guessing.
>  
>  
> -# Wake
> -
> -# From Vernice Anderson, Personal Secretary to Philip Jessup,
> -# US Ambassador At Large (oral history interview, 1971-02-02):
> -#
> -# Saturday, the 14th [of October, 1950] - ...  The time was all the
> -# more confusing at that point, because we had crossed the
> -# International Date Line, thus getting two Sundays.  Furthermore, we
> -# discovered that Wake Island had two hours of daylight saving time
> -# making calculation of time in Washington difficult if not almost
> -# impossible.
> -#
> -# https://www.trumanlibrary.org/oralhist/andrsonv.htm
> -
> -# From Paul Eggert (2003-03-23):
> -# We have no other report of DST in Wake Island, so omit this info for now.
> -
> -# See also the commentary for Micronesia.
> -
> -
>  ###############################################################################
>  
>  # The International Date Line
> diff --git a/backward b/backward
> index 9b5e6d0..0d9ecfa 100644
> --- a/backward
> +++ b/backward
> @@ -5,30 +5,35 @@
>  
>  # This file provides links between current names for timezones
>  # and their old names.  Many names changed in late 1993.
> +# Many others were moved here in 2021.  Several of these names are
> +# also present in the file 'backzone', which has data important only
> +# for pre-1970 timestamps and so is out of scope for tzdb proper.
>  
>  # Link	TARGET			LINK-NAME
> +Link	Etc/GMT			Africa/Abidjan
> +Link	Etc/GMT			Africa/Accra
>  Link	Africa/Nairobi		Africa/Addis_Ababa
>  Link	Africa/Nairobi		Africa/Asmara
>  Link	Africa/Nairobi		Africa/Asmera
> -Link	Africa/Abidjan		Africa/Bamako
> +Link	Etc/GMT			Africa/Bamako
>  Link	Africa/Lagos		Africa/Bangui
> -Link	Africa/Abidjan		Africa/Banjul
> +Link	Etc/GMT			Africa/Banjul
>  Link	Africa/Maputo		Africa/Blantyre
>  Link	Africa/Lagos		Africa/Brazzaville
>  Link	Africa/Maputo		Africa/Bujumbura
> -Link	Africa/Abidjan		Africa/Conakry
> -Link	Africa/Abidjan		Africa/Dakar
> +Link	Etc/GMT			Africa/Conakry
> +Link	Etc/GMT			Africa/Dakar
>  Link	Africa/Nairobi		Africa/Dar_es_Salaam
>  Link	Africa/Nairobi		Africa/Djibouti
>  Link	Africa/Lagos		Africa/Douala
> -Link	Africa/Abidjan		Africa/Freetown
> +Link	Etc/GMT			Africa/Freetown
>  Link	Africa/Maputo		Africa/Gaborone
>  Link	Africa/Maputo		Africa/Harare
>  Link	Africa/Nairobi		Africa/Kampala
>  Link	Africa/Maputo		Africa/Kigali
>  Link	Africa/Lagos		Africa/Kinshasa
>  Link	Africa/Lagos		Africa/Libreville
> -Link	Africa/Abidjan		Africa/Lome
> +Link	Etc/GMT			Africa/Lome
>  Link	Africa/Lagos		Africa/Luanda
>  Link	Africa/Maputo		Africa/Lubumbashi
>  Link	Africa/Maputo		Africa/Lusaka
> @@ -37,75 +42,95 @@ Link	Africa/Johannesburg	Africa/Maseru
>  Link	Africa/Johannesburg	Africa/Mbabane
>  Link	Africa/Nairobi		Africa/Mogadishu
>  Link	Africa/Lagos		Africa/Niamey
> -Link	Africa/Abidjan		Africa/Nouakchott
> -Link	Africa/Abidjan		Africa/Ouagadougou
> +Link	Etc/GMT			Africa/Nouakchott
> +Link	Etc/GMT			Africa/Ouagadougou
>  Link	Africa/Lagos		Africa/Porto-Novo
> -Link	Africa/Abidjan		Africa/Timbuktu
> -Link	America/Port_of_Spain	America/Anguilla
> -Link	America/Port_of_Spain	America/Antigua
> +Link	Etc/GMT			Africa/Timbuktu
> +Link	America/Puerto_Rico	America/Anguilla
> +Link	America/Puerto_Rico	America/Antigua
>  Link	America/Argentina/Catamarca	America/Argentina/ComodRivadavia
> -Link	America/Curacao		America/Aruba
> +Link	America/Puerto_Rico	America/Aruba
> +Link	America/Panama		America/Atikokan
>  Link	America/Adak		America/Atka
> +Link	America/Puerto_Rico	America/Blanc-Sablon
>  Link	America/Argentina/Buenos_Aires	America/Buenos_Aires
>  Link	America/Argentina/Catamarca	America/Catamarca
> +Link	Etc/GMT+3		America/Cayenne
>  Link	America/Panama		America/Cayman
> -Link	America/Atikokan	America/Coral_Harbour
> +Link	America/Panama		America/Coral_Harbour
>  Link	America/Argentina/Cordoba	America/Cordoba
> -Link	America/Port_of_Spain	America/Dominica
> +Link	America/Phoenix		America/Creston
> +Link	America/Puerto_Rico	America/Curacao
> +Link	America/Puerto_Rico	America/Dominica
>  Link	America/Tijuana		America/Ensenada
>  Link	America/Indiana/Indianapolis	America/Fort_Wayne
>  Link	America/Nuuk		America/Godthab
> -Link	America/Port_of_Spain	America/Grenada
> -Link	America/Port_of_Spain	America/Guadeloupe
> +Link	America/Puerto_Rico	America/Grenada
> +Link	America/Puerto_Rico	America/Guadeloupe
>  Link	America/Indiana/Indianapolis	America/Indianapolis
>  Link	America/Argentina/Jujuy	America/Jujuy
>  Link	America/Indiana/Knox	America/Knox_IN
> -Link	America/Curacao		America/Kralendijk
> +Link	America/Puerto_Rico	America/Kralendijk
> +Link	Etc/GMT+4		America/La_Paz
>  Link	America/Kentucky/Louisville	America/Louisville
> -Link	America/Curacao		America/Lower_Princes
> -Link	America/Port_of_Spain	America/Marigot
> +Link	America/Puerto_Rico	America/Lower_Princes
> +Link	America/Puerto_Rico	America/Marigot
>  Link	America/Argentina/Mendoza	America/Mendoza
>  Link	America/Toronto		America/Montreal
> -Link	America/Port_of_Spain	America/Montserrat
> +Link	America/Puerto_Rico	America/Montserrat
> +Link	America/Toronto		America/Nassau
> +Link	America/Puerto_Rico	America/Port_of_Spain
>  Link	America/Rio_Branco	America/Porto_Acre
>  Link	America/Argentina/Cordoba	America/Rosario
>  Link	America/Tijuana		America/Santa_Isabel
>  Link	America/Denver		America/Shiprock
> -Link	America/Port_of_Spain	America/St_Barthelemy
> -Link	America/Port_of_Spain	America/St_Kitts
> -Link	America/Port_of_Spain	America/St_Lucia
> -Link	America/Port_of_Spain	America/St_Thomas
> -Link	America/Port_of_Spain	America/St_Vincent
> -Link	America/Port_of_Spain	America/Tortola
> -Link	America/Port_of_Spain	America/Virgin
> +Link	America/Puerto_Rico	America/St_Barthelemy
> +Link	America/Puerto_Rico	America/St_Kitts
> +Link	America/Puerto_Rico	America/St_Lucia
> +Link	America/Puerto_Rico	America/St_Thomas
> +Link	America/Puerto_Rico	America/St_Vincent
> +Link	America/Puerto_Rico	America/Tortola
> +Link	America/Puerto_Rico	America/Virgin
> +Link	Etc/GMT-10		Antarctica/DumontDUrville
>  Link	Pacific/Auckland	Antarctica/McMurdo
>  Link	Pacific/Auckland	Antarctica/South_Pole
> -Link	Europe/Oslo		Arctic/Longyearbyen
> -Link	Asia/Riyadh		Asia/Aden
> +Link	Etc/GMT-3		Antarctica/Syowa
> +Link	Etc/GMT-6		Antarctica/Vostok
> +Link	Europe/Berlin		Arctic/Longyearbyen
> +Link	Etc/GMT-3		Asia/Aden
>  Link	Asia/Ashgabat		Asia/Ashkhabad
>  Link	Asia/Qatar		Asia/Bahrain
> +Link	Etc/GMT-7		Asia/Bangkok
> +Link	Etc/GMT-8		Asia/Brunei
>  Link	Asia/Kolkata		Asia/Calcutta
>  Link	Asia/Shanghai		Asia/Chongqing
>  Link	Asia/Shanghai		Asia/Chungking
>  Link	Asia/Dhaka		Asia/Dacca
> +Link	Etc/GMT-4		Asia/Dubai
>  Link	Asia/Shanghai		Asia/Harbin
>  Link	Europe/Istanbul		Asia/Istanbul
> -Link	Asia/Urumqi		Asia/Kashgar
> +Link	Etc/GMT-6		Asia/Kashgar
>  Link	Asia/Kathmandu		Asia/Katmandu
> -Link	Asia/Riyadh		Asia/Kuwait
> +Link	Asia/Singapore		Asia/Kuala_Lumpur
> +Link	Etc/GMT-8		Asia/Kuching
> +Link	Etc/GMT-3		Asia/Kuwait
>  Link	Asia/Macau		Asia/Macao
> -Link	Asia/Dubai		Asia/Muscat
> -Link	Asia/Bangkok		Asia/Phnom_Penh
> +Link	Etc/GMT-4		Asia/Muscat
> +Link	Etc/GMT-7		Asia/Phnom_Penh
>  Link	Asia/Yangon		Asia/Rangoon
> +Link	Etc/GMT-3		Asia/Riyadh
>  Link	Asia/Ho_Chi_Minh	Asia/Saigon
>  Link	Asia/Jerusalem		Asia/Tel_Aviv
>  Link	Asia/Thimphu		Asia/Thimbu
>  Link	Asia/Makassar		Asia/Ujung_Pandang
>  Link	Asia/Ulaanbaatar	Asia/Ulan_Bator
> -Link	Asia/Bangkok		Asia/Vientiane
> +Link	Etc/GMT-6		Asia/Urumqi
> +Link	Etc/GMT-7		Asia/Vientiane
>  Link	Atlantic/Faroe		Atlantic/Faeroe
> -Link	Europe/Oslo		Atlantic/Jan_Mayen
> -Link	Africa/Abidjan		Atlantic/St_Helena
> +Link	Europe/Berlin		Atlantic/Jan_Mayen
> +Link	Etc/GMT			Atlantic/Reykjavik
> +Link	Etc/GMT+2		Atlantic/South_Georgia
> +Link	Etc/GMT			Atlantic/St_Helena
>  Link	Australia/Sydney	Australia/ACT
>  Link	Australia/Sydney	Australia/Canberra
>  Link	Australia/Hobart	Australia/Currie
> @@ -139,19 +164,25 @@ Link	America/Havana		Cuba
>  Link	Africa/Cairo		Egypt
>  Link	Europe/Dublin		Eire
>  Link	Etc/UTC			Etc/UCT
> +Link	Europe/Brussels		Europe/Amsterdam
>  Link	Europe/London		Europe/Belfast
>  Link	Europe/Prague		Europe/Bratislava
>  Link	Europe/Zurich		Europe/Busingen
> +Link	Europe/Berlin		Europe/Copenhagen
>  Link	Europe/London		Europe/Guernsey
>  Link	Europe/London		Europe/Isle_of_Man
>  Link	Europe/London		Europe/Jersey
>  Link	Europe/Belgrade		Europe/Ljubljana
> +Link	Europe/Brussels		Europe/Luxembourg
>  Link	Europe/Helsinki		Europe/Mariehamn
> +Link	Europe/Paris		Europe/Monaco
>  Link	Asia/Nicosia		Europe/Nicosia
> +Link	Europe/Berlin		Europe/Oslo
>  Link	Europe/Belgrade		Europe/Podgorica
>  Link	Europe/Rome		Europe/San_Marino
>  Link	Europe/Belgrade		Europe/Sarajevo
>  Link	Europe/Belgrade		Europe/Skopje
> +Link	Europe/Berlin		Europe/Stockholm
>  Link	Europe/Chisinau		Europe/Tiraspol
>  Link	Europe/Zurich		Europe/Vaduz
>  Link	Europe/Rome		Europe/Vatican
> @@ -163,10 +194,16 @@ Link	Etc/GMT			GMT-0
>  Link	Etc/GMT			GMT0
>  Link	Etc/GMT			Greenwich
>  Link	Asia/Hong_Kong		Hongkong
> -Link	Atlantic/Reykjavik	Iceland
> +Link	Etc/GMT			Iceland
>  Link	Africa/Nairobi		Indian/Antananarivo
> +Link	Etc/GMT-7		Indian/Christmas
> +Link	Asia/Yangon		Indian/Cocos
>  Link	Africa/Nairobi		Indian/Comoro
> +Link	Etc/GMT-5		Indian/Kerguelen
> +Link	Etc/GMT-4		Indian/Mahe
> +Link	Etc/GMT-5		Indian/Maldives
>  Link	Africa/Nairobi		Indian/Mayotte
> +Link	Etc/GMT-4		Indian/Reunion
>  Link	Asia/Tehran		Iran
>  Link	Asia/Jerusalem		Israel
>  Link	America/Jamaica		Jamaica
> @@ -180,13 +217,25 @@ Link	Pacific/Auckland	NZ
>  Link	Pacific/Chatham		NZ-CHAT
>  Link	America/Denver		Navajo
>  Link	Asia/Shanghai		PRC
> +Link	Etc/GMT-10		Pacific/Chuuk
> +Link	Etc/GMT-12		Pacific/Funafuti
> +Link	Etc/GMT+9		Pacific/Gambier
> +Link	Etc/GMT-11		Pacific/Guadalcanal
>  Link	Pacific/Honolulu	Pacific/Johnston
> +Link	Etc/GMT-12		Pacific/Majuro
>  Link	Pacific/Pago_Pago	Pacific/Midway
> -Link	Pacific/Pohnpei		Pacific/Ponape
> +Link	Etc/GMT-9		Pacific/Palau
> +Link	Etc/GMT-11		Pacific/Pohnpei
> +Link	Etc/GMT-11		Pacific/Ponape
> +Link	Etc/GMT-10		Pacific/Port_Moresby
>  Link	Pacific/Guam		Pacific/Saipan
>  Link	Pacific/Pago_Pago	Pacific/Samoa
> -Link	Pacific/Chuuk		Pacific/Truk
> -Link	Pacific/Chuuk		Pacific/Yap
> +Link	Etc/GMT+10		Pacific/Tahiti
> +Link	Etc/GMT-12		Pacific/Tarawa
> +Link	Etc/GMT-10		Pacific/Truk
> +Link	Etc/GMT-12		Pacific/Wake
> +Link	Etc/GMT-12		Pacific/Wallis
> +Link	Etc/GMT-10		Pacific/Yap
>  Link	Europe/Warsaw		Poland
>  Link	Europe/Lisbon		Portugal
>  Link	Asia/Taipei		ROC
> diff --git a/backzone b/backzone
> index 8e4f97a..b58f4d8 100644
> --- a/backzone
> +++ b/backzone
> @@ -68,6 +68,96 @@
>  #
>  # As explained in the zic man page, the zone columns are:
>  # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> +# and the rule columns are:
> +# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
> +
> +
> +# Côte d'Ivoire / Ivory Coast
> +Zone	Africa/Abidjan	-0:16:08 -	LMT	1912
> +			 0:00	-	GMT
> +
> +
> +# Ghana
> +
> +# From P Chan (2020-11-20):
> +# Interpretation Amendment Ordinance, 1915 (No.24 of 1915) [1915-11-02]
> +# Ordinances of the Gold Coast, Ashanti, Northern Territories 1915, p 69-71
> +# https://books.google.com/books?id=ErA-AQAAIAAJ&pg=PA70
> +# This Ordinance added "'Time' shall mean Greenwich Mean Time" to the
> +# Interpretation Ordinance, 1876.
> +#
> +# Determination of the Time Ordinance, 1919 (No. 18 of 1919) [1919-11-24]
> +# Ordinances of the Gold Coast, Ashanti, Northern Territories 1919, p 75-76
> +# https://books.google.com/books?id=MbA-AQAAIAAJ&pg=PA75
> +# This Ordinance removed the previous definition of time and introduced DST.
> +#
> +# Time Determination Ordinance (Cap. 214)
> +# The Laws of the Gold Coast (including Togoland Under British Mandate)
> +# Vol. II (1937), p 2328
> +# https://books.google.com/books?id=Z7M-AQAAIAAJ&pg=PA2328
> +# Revised edition of the 1919 Ordinance.
> +#
> +# Time Determination (Amendment) Ordinance, 1940 (No. 9 of 1940) [1940-04-06]
> +# Annual Volume of the Laws of the Gold Coast:
> +# Containing All Legislation Enacted During Year 1940, p 22
> +# https://books.google.com/books?id=1ao-AQAAIAAJ&pg=PA22
> +# This Ordinance changed the forward transition from September to May.
> +#
> +# Defence (Time Determination Ordinance Amendment) Regulations, 1942
> +# (Regulations No. 6 of 1942) [1942-01-31, commenced on 1942-02-08]
> +# Annual Volume of the Laws of the Gold Coast:
> +# Containing All Legislation Enacted During Year 1942, p 48
> +# https://books.google.com/books?id=Das-AQAAIAAJ&pg=PA48
> +# These regulations advanced the [standard] time by thirty minutes.
> +#
> +# Defence (Time Determination Ordinance Amendment (No.2)) Regulations,
> +# 1942 (Regulations No. 28 of 1942) [1942-04-25]
> +# Annual Volume of the Laws of the Gold Coast:
> +# Containing All Legislation Enacted During Year 1942, p 87
> +# https://books.google.com/books?id=Das-AQAAIAAJ&pg=PA87
> +# These regulations abolished DST and changed the time to GMT+0:30.
> +#
> +# Defence (Revocation) (No.4) Regulations, 1945 (Regulations No. 45 of
> +# 1945) [1945-10-24, commenced on 1946-01-06]
> +# Annual Volume of the Laws of the Gold Coast:
> +# Containing All Legislation Enacted During Year 1945, p 256
> +# https://books.google.com/books?id=9as-AQAAIAAJ&pg=PA256
> +# These regulations revoked the previous two sets of Regulations.
> +#
> +# Time Determination (Amendment) Ordinance, 1945 (No. 18 of 1945) [1946-01-06]
> +# Annual Volume of the Laws of the Gold Coast:
> +# Containing All Legislation Enacted During Year 1945, p 69
> +# https://books.google.com/books?id=9as-AQAAIAAJ&pg=PA69
> +# This Ordinance abolished DST.
> +#
> +# Time Determination (Amendment) Ordinance, 1950 (No. 26 of 1950) [1950-07-22]
> +# Annual Volume of the Laws of the Gold Coast:
> +# Containing All Legislation Enacted During Year 1950, p 35
> +# https://books.google.com/books?id=e60-AQAAIAAJ&pg=PA35
> +# This Ordinance restored DST but with thirty minutes offset.
> +#
> +# Time Determination Ordinance (Cap. 264)
> +# The Laws of the Gold Coast, Vol. V (1954), p 380
> +# https://books.google.com/books?id=Mqc-AQAAIAAJ&pg=PA380
> +# Revised edition of the Time Determination Ordinance.
> +#
> +# Time Determination (Amendment) Ordinance, 1956 (No. 21 of 1956) [1956-08-29]
> +# Annual Volume of the Ordinances of the Gold Coast Enacted During the
> +# Year 1956, p 83
> +# https://books.google.com/books?id=VLE-AQAAIAAJ&pg=PA83
> +# This Ordinance abolished DST.
> +
> +Rule	Ghana	1919	only	-	Nov	24	0:00	0:20	+0020
> +Rule	Ghana	1920	1942	-	Jan	 1	2:00	0	GMT
> +Rule	Ghana	1920	1939	-	Sep	 1	2:00	0:20	+0020
> +Rule	Ghana	1940	1941	-	May	 1	2:00	0:20	+0020
> +Rule	Ghana	1950	1955	-	Sep	 1	2:00	0:30	+0030
> +Rule	Ghana	1951	1956	-	Jan	 1	2:00	0	GMT
> +
> +Zone	Africa/Accra	-0:00:52 -	LMT	1915 Nov  2
> +			 0:00	Ghana	%s	1942 Feb  8
> +			 0:30	-	+0030	1946 Jan  6
> +			 0:00	Ghana	%s
>  
>  # Ethiopia
>  # From Paul Eggert (2014-07-31):
> @@ -201,7 +291,6 @@ Zone	Africa/Douala	0:38:48	-	LMT	1912
>  # https://mm.icann.org/pipermail/tz/2021-February/029866.html
>  # Go with the above.
>  
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
>  Rule	SL	1932	only	-	Dec	 1	 0:00	0:20	-0040
>  Rule	SL	1933	1938	-	Mar	31	24:00	0	-01
>  Rule	SL	1933	1939	-	Aug	31	24:00	0:20	-0040
> @@ -350,6 +439,90 @@ Zone	America/Aruba	-4:40:24 -	LMT	1912 Feb 12 # Oranjestad
>  			-4:30	-	-0430	1965
>  			-4:00	-	AST
>  
> +# Atikokan, Ontario
> +
> +# From Paul Eggert (1997-10-17):
> +# Mark Brader writes that an article in the 1997-10-14 Toronto Star
> +# says that Atikokan, Ontario currently does not observe DST,
> +# but will vote on 11-10 whether to use EST/EDT.
> +# He also writes that the Ontario Time Act (1990, Chapter T.9)
> +# http://www.gov.on.ca/MBS/english/publications/statregs/conttext.html
> +# says that Ontario east of 90W uses EST/EDT, and west of 90W uses CST/CDT.
> +# Officially Atikokan is therefore on CST/CDT, and most likely this report
> +# concerns a non-official time observed as a matter of local practice.
> +#
> +# From Paul Eggert (2000-10-02):
> +# Matthews and Vincent (1998) write that Atikokan, Pickle Lake, and
> +# New Osnaburgh observe CST all year, that Big Trout Lake observes
> +# CST/CDT, and that Upsala and Shebandowan observe EST/EDT, all in
> +# violation of the official Ontario rules.
> +#
> +# From Paul Eggert (2006-07-09):
> +# Chris Walton (2006-07-06) mentioned an article by Stephanie MacLellan in the
> +# 2005-07-21 Chronicle-Journal, which said:
> +#
> +#	The clocks in Atikokan stay set on standard time year-round.
> +#	This means they spend about half the time on central time and
> +#	the other half on eastern time.
> +#
> +#	For the most part, the system works, Mayor Dennis Brown said.
> +#
> +#	"The majority of businesses in Atikokan deal more with Eastern
> +#	Canada, but there are some that deal with Western Canada," he
> +#	said.  "I don't see any changes happening here."
> +#
> +# Walton also writes "Supposedly Pickle Lake and Mishkeegogamang
> +# [New Osnaburgh] follow the same practice."
> +
> +# From Garry McKinnon (2006-07-14) via Chris Walton:
> +# I chatted with a member of my board who has an outstanding memory
> +# and a long history in Atikokan (and in the telecom industry) and he
> +# can say for certain that Atikokan has been practicing the current
> +# time keeping since 1952, at least.
> +
> +# From Paul Eggert (2006-07-17):
> +# Shanks & Pottenger say that Atikokan has agreed with Rainy River
> +# ever since standard time was introduced, but the information from
> +# McKinnon sounds more authoritative.  For now, assume that Atikokan
> +# switched to EST immediately after WWII era daylight saving time
> +# ended.  This matches the old (less-populous) America/Coral_Harbour
> +# entry since our cutoff date of 1970, so we can move
> +# America/Coral_Harbour to the 'backward' file.
> +
> +Zone America/Atikokan	-6:06:28 -	LMT	1895
> +			-6:00	Canada	C%sT	1940 Sep 29
> +			-6:00	1:00	CDT	1942 Feb  9  2:00s
> +			-6:00	Canada	C%sT	1945 Sep 30  2:00
> +			-5:00	-	EST
> +
> +# Quebec east of Natashquan
> +
> +# From Paul Eggert (2021-05-09):
> +# H. David Matthews and Mary Vincent's map
> +# "It's about TIME", _Canadian Geographic_ (September-October 1998)
> +# http://www.canadiangeographic.ca/Magazine/SO98/alacarte.asp
> +# says that Quebec east of the -63 meridian is supposed to observe
> +# AST, but residents as far east as Natashquan use EST/EDT, and
> +# residents east of Natashquan use AST.
> +# The Quebec department of justice writes in
> +# "The situation in Minganie and Basse-Côte-Nord"
> +# https://www.justice.gouv.qc.ca/en/department/ministre/functions-and-responsabilities/legal-time-in-quebec/the-situation-in-minganie-and-basse-cote-nord/
> +# that the coastal strip from just east of Natashquan to Blanc-Sablon
> +# observes Atlantic standard time all year round.
> +# This common practice was codified into law as of 2007; see Legal Time Act,
> +# CQLR c T-5.1 <http://legisquebec.gouv.qc.ca/en/ShowDoc/cs/T-5.1>.
> +# For lack of better info, guess this practice began around 1970, contra to
> +# Shanks & Pottenger who have this region observing AST/ADT.
> +
> +Zone America/Blanc-Sablon -3:48:28 -	LMT	1884
> +			-4:00	Canada	A%sT	1970
> +			-4:00	-	AST
> +
> +# French Guiana
> +Zone	America/Cayenne	-3:29:20 -	LMT	1911 Jul
> +			-4:00	-	-04	1967 Oct
> +			-3:00	-	-03
> +
>  # Cayman Is
>  Zone	America/Cayman	-5:25:32 -	LMT	1890     # Georgetown
>  			-5:07:10 -	KMT	1912 Feb # Kingston Mean Time
> @@ -370,6 +543,85 @@ Zone America/Coral_Harbour -5:32:40 -	LMT	1884
>  			-5:00	NT_YK	E%sT	1946
>  			-5:00	-	EST
>  
> +# From Chris Walton (2011-12-01):
> +# There are two areas within the Canadian province of British Columbia
> +# that do not currently observe daylight saving:
> +# a) The Creston Valley (includes the town of Creston and surrounding area)
> +# b) The eastern half of the Peace River Regional District
> +# (includes the cities of Dawson Creek and Fort St. John)
> +
> +# Earlier this year I stumbled across a detailed article about the time
> +# keeping history of Creston; it was written by Tammy Hardwick who is the
> +# manager of the Creston & District Museum. The article was written in May 2009.
> +# http://www.ilovecreston.com/?p=articles&t=spec&ar=260
> +# According to the article, Creston has not changed its clocks since June 1918.
> +# i.e. Creston has been stuck on UT-7 for 93 years.
> +# Dawson Creek, on the other hand, changed its clocks as recently as April 1972.
> +
> +# Unfortunately the exact date for the time change in June 1918 remains
> +# unknown and will be difficult to ascertain.  I e-mailed Tammy a few months
> +# ago to ask if Sunday June 2 was a reasonable guess.  She said it was just
> +# as plausible as any other date (in June).  She also said that after writing
> +# the article she had discovered another time change in 1916; this is the
> +# subject of another article which she wrote in October 2010.
> +# http://www.creston.museum.bc.ca/index.php?module=comments&uop=view_comment&cm+id=56
> +
> +# Here is a summary of the three clock change events in Creston's history:
> +# 1. 1884 or 1885: adoption of Mountain Standard Time (GMT-7)
> +# Exact date unknown
> +# 2. Oct 1916: switch to Pacific Standard Time (GMT-8)
> +# Exact date in October unknown; Sunday October 1 is a reasonable guess.
> +# 3. June 1918: switch to Pacific Daylight Time (GMT-7)
> +# Exact date in June unknown; Sunday June 2 is a reasonable guess.
> +# note 1:
> +# On Oct 27/1918 when daylight saving ended in the rest of Canada,
> +# Creston did not change its clocks.
> +# note 2:
> +# During WWII when the Federal Government legislated a mandatory clock change,
> +# Creston did not oblige.
> +# note 3:
> +# There is no guarantee that Creston will remain on Mountain Standard Time
> +# (UTC-7) forever.
> +# The subject was debated at least once this year by the town Council.
> +# http://www.bclocalnews.com/kootenay_rockies/crestonvalleyadvance/news/116760809.html
> +
> +# During a period WWII, summer time (Daylight saying) was mandatory in Canada.
> +# In Creston, that was handled by shifting the area to PST (-8:00) then applying
> +# summer time to cause the offset to be -7:00, the same as it had been before
> +# the change.  It can be argued that the timezone abbreviation during this
> +# period should be PDT rather than MST, but that doesn't seem important enough
> +# (to anyone) to further complicate the rules.
> +
> +# The transition dates (and times) are guesses.
> +
> +Zone America/Creston	-7:46:04 -	LMT	1884
> +			-7:00	-	MST	1916 Oct 1
> +			-8:00	-	PST	1918 Jun 2
> +			-7:00	-	MST
> +
> +# Curaçao
> +# Milne gives 4:35:46.9 for Curaçao mean time; round to nearest.
> +#
> +# From Paul Eggert (2006-03-22):
> +# Shanks & Pottenger say that The Bottom and Philipsburg have been at
> +# -4:00 since standard time was introduced on 1912-03-02; and that
> +# Kralendijk and Rincon used Kralendijk Mean Time (-4:33:08) from
> +# 1912-02-02 to 1965-01-01.  The former is dubious, since S&P also say
> +# Saba Island has been like Curaçao.
> +# This all predates our 1970 cutoff, though.
> +#
> +# By July 2007 Curaçao and St Maarten are planned to become
> +# associated states within the Netherlands, much like Aruba;
> +# Bonaire, Saba and St Eustatius would become directly part of the
> +# Netherlands as Kingdom Islands.  This won't affect their time zones
> +# though, as far as we know.
> +#
> +Zone	America/Curacao	-4:35:47 -	LMT	1912 Feb 12 # Willemstad
> +			-4:30	-	-0430	1965
> +			-4:00	-	AST
> +Link	America/Curacao	America/Kralendijk
> +Link	America/Curacao	America/Lower_Princes
> +
>  # Dominica
>  Zone America/Dominica	-4:05:36 -	LMT	1911 Jul  1  0:01 # Roseau
>  			-4:00	-	AST
> @@ -392,6 +644,12 @@ Zone	America/Grenada	-4:07:00 -	LMT	1911 Jul # St George's
>  Zone America/Guadeloupe	-4:06:08 -	LMT	1911 Jun  8 # Pointe-à-Pitre
>  			-4:00	 -	AST
>  
> +# Bolivia
> +Zone	America/La_Paz	-4:32:36 -	LMT	1890
> +			-4:32:36 -	CMT	1931 Oct 15 # Calamarca MT
> +			-4:32:36 1:00	BST	1932 Mar 21 # Bolivia ST
> +			-4:00	-	-04
> +
>  # Canada
>  #
>  # From Paul Eggert (2015-03-24):
> @@ -403,7 +661,6 @@ Zone America/Guadeloupe	-4:06:08 -	LMT	1911 Jun  8 # Pointe-à-Pitre
>  # Pottenger data.  The post-1970 entries have been corrected, but the
>  # pre-1970 entries are unchecked and probably have errors.
>  #
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
>  Rule	Mont	1917	only	-	Mar	25	2:00	1:00	D
>  Rule	Mont	1917	only	-	Apr	24	0:00	0	S
>  Rule	Mont	1919	only	-	Mar	31	2:30	1:00	D
> @@ -439,6 +696,48 @@ Zone America/Montreal	-4:54:16 -	LMT	1884
>  Zone America/Montserrat	-4:08:52 -	LMT	1911 Jul  1  0:01 # Cork Hill
>  			-4:00	-	AST
>  
> +# The Bahamas
> +#
> +# For 1899 Milne gives -5:09:29.5; round that.
> +#
> +# From P Chan (2020-11-27, corrected on 2020-12-02):
> +# There were two periods of DST observed in 1942-1945: 1942-05-01
> +# midnight to 1944-12-31 midnight and 1945-02-01 to 1945-10-17 midnight.
> +# "midnight" should mean 24:00 from the context.
> +#
> +# War Time Order 1942 [1942-05-01] and War Time (No. 2) Order 1942  [1942-09-29]
> +# Appendix to the Statutes of 7 George VI. and the Year 1942. p 34, 43
> +# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA3-PA34
> +# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA3-PA43
> +#
> +# War Time Order 1943 [1943-03-31] and War Time Order 1944 [1943-12-29]
> +# Appendix to the Statutes of 8 George VI. and the Year 1943. p 9-10, 28-29
> +# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA4-PA9
> +# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA4-PA28
> +#
> +# War Time Order 1945 [1945-01-31] and the Order which revoke War Time Order
> +# 1945 [1945-10-16] Appendix to the Statutes of 9 George VI. and the Year
> +# 1945. p 160, 247-248
> +# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA6-PA160
> +# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA6-PA247
> +#
> +# From Sue Williams (2006-12-07):
> +# The Bahamas announced about a month ago that they plan to change their DST
> +# rules to sync with the U.S. starting in 2007....
> +# http://www.jonesbahamas.com/?c=45&a=10412
> +
> +Rule	Bahamas	1942	only	-	May	 1	24:00	1:00	W
> +Rule	Bahamas	1944	only	-	Dec	31	24:00	0	S
> +Rule	Bahamas	1945	only	-	Feb	 1	0:00	1:00	W
> +Rule	Bahamas	1945	only	-	Aug	14	23:00u	1:00	P # Peace
> +Rule	Bahamas	1945	only	-	Oct	17	24:00	0	S
> +Rule	Bahamas	1964	1975	-	Oct	lastSun	2:00	0	S
> +Rule	Bahamas	1964	1975	-	Apr	lastSun	2:00	1:00	D
> +
> +Zone	America/Nassau	-5:09:30 -	LMT	1912 Mar 2
> +			-5:00	Bahamas	E%sT	1976
> +			-5:00	US	E%sT
> +
>  # United States
>  #
>  # From Paul Eggert (2018-03-18):
> @@ -463,6 +762,13 @@ Zone America/Montserrat	-4:08:52 -	LMT	1911 Jul  1  0:01 # Cork Hill
>  # https://cdnc.ucr.edu/cgi-bin/cdnc?a=d&d=DS19470110
>  # front page reports on end.
>  
> +# Trinidad and Tobago
> +Zone America/Port_of_Spain -4:06:04 -	LMT	1912 Mar 2
> +			-4:00	-	AST
> +Link America/Port_of_Spain America/Marigot
> +Link America/Port_of_Spain America/St_Barthelemy
> +Link America/Port_of_Spain America/Virgin
> +
>  # Argentina
>  # This entry was intended for the following areas, but has been superseded by
>  # more detailed zones.
> @@ -486,7 +792,7 @@ Zone America/St_Lucia	-4:04:00 -	LMT	1890 # Castries
>  			-4:04:00 -	CMT	1912 # Castries Mean Time
>  			-4:00	-	AST
>  
> -# Virgin Is
> +# US Virgin Is
>  Zone America/St_Thomas	-4:19:44 -	LMT	1911 Jul # Charlotte Amalie
>  			-4:00	-	AST
>  
> @@ -499,11 +805,65 @@ Zone America/St_Vincent	-4:04:56 -	LMT	1890 # Kingstown
>  Zone America/Tortola	-4:18:28 -	LMT	1911 Jul # Road Town
>  			-4:00	-	AST
>  
> +# Dumont d'Urville, Île des Pétrels, -6640+14001, since 1956-11
> +# <https://en.wikipedia.org/wiki/Dumont_d'Urville_Station> (2005-12-05)
> +#
> +# Another base at Port-Martin, 50km east, began operation in 1947.
> +# It was destroyed by fire on 1952-01-14.
> +#
> +Zone Antarctica/DumontDUrville 0 -	-00	1947
> +			10:00	-	+10	1952 Jan 14
> +			0	-	-00	1956 Nov
> +			10:00	-	+10
> +
>  # McMurdo, Ross Island, since 1955-12
>  Zone Antarctica/McMurdo	0	-	-00	1956
>  			12:00	NZ	NZ%sT
>  Link Antarctica/McMurdo Antarctica/South_Pole
>  
> +# Syowa, Antarctica
> +#
> +# From Hideyuki Suzuki (1999-02-06):
> +# In all Japanese stations, +0300 is used as the standard time.
> +#
> +# Syowa station, which is the first antarctic station of Japan,
> +# was established on 1957-01-29.  Since Syowa station is still the main
> +# station of Japan, it's appropriate for the principal location.
> +Zone Antarctica/Syowa	0	-	-00	1957 Jan 29
> +			3:00	-	+03
> +# See:
> +# NIPR Antarctic Research Activities (1999-08-17)
> +# http://www.nipr.ac.jp/english/ara01.html
> +
> +# Vostok, Antarctica
> +#
> +# Vostok, since 1957-12-16, temporarily closed 1994-02/1994-11
> +# From Craig Mundell (1994-12-15):
> +# http://quest.arc.nasa.gov/antarctica/QA/computers/Directions,Time,ZIP
> +# Vostok, which is one of the Russian stations, is set on the same
> +# time as Moscow, Russia.
> +#
> +# From Lee Hotz (2001-03-08):
> +# I queried the folks at Columbia who spent the summer at Vostok and this is
> +# what they had to say about time there:
> +# "in the US Camp (East Camp) we have been on New Zealand (McMurdo)
> +# time, which is 12 hours ahead of GMT. The Russian Station Vostok was
> +# 6 hours behind that (although only 2 miles away, i.e. 6 hours ahead
> +# of GMT). This is a time zone I think two hours east of Moscow. The
> +# natural time zone is in between the two: 8 hours ahead of GMT."
> +#
> +# From Paul Eggert (2001-05-04):
> +# This seems to be hopelessly confusing, so I asked Lee Hotz about it
> +# in person.  He said that some Antarctic locations set their local
> +# time so that noon is the warmest part of the day, and that this
> +# changes during the year and does not necessarily correspond to mean
> +# solar noon.  So the Vostok time might have been whatever the clocks
> +# happened to be during their visit.  So we still don't really know what time
> +# it is at Vostok.  But we'll guess +06.
> +#
> +Zone Antarctica/Vostok	0	-	-00	1957 Dec 16
> +			6:00	-	+06
> +
>  # Yemen
>  # Milne says 2:59:54 was the meridian of the saluting battery at Aden,
>  # and that Yemen was at 1:55:56, the meridian of the Hagia Sophia.
> @@ -542,6 +902,16 @@ Zone	Asia/Bahrain	3:22:20 -	LMT	1941 Jul 20  # Manamah
>  			4:00	-	+04	1972 Jun
>  			3:00	-	+03
>  
> +# Thailand
> +Zone	Asia/Bangkok	6:42:04	-	LMT	1880
> +			6:42:04	-	BMT	1920 Apr # Bangkok Mean Time
> +			7:00	-	+07
> +
> +# Brunei
> +Zone	Asia/Brunei	7:39:40 -	LMT	1926 Mar # Bandar Seri Begawan
> +			7:30	-	+0730	1933
> +			8:00	-	+08
> +
>  # India
>  #
>  # From Paul Eggert (2014-09-06):
> @@ -567,6 +937,10 @@ Zone	Asia/Chongqing	7:06:20	-	LMT	1928     # or Chungking
>  			8:00	PRC	C%sT
>  Link Asia/Chongqing Asia/Chungking
>  
> +# United Arab Emirates
> +Zone	Asia/Dubai	3:41:12 -	LMT	1920
> +			4:00	-	+04
> +
>  # Vietnam
>  # From Paul Eggert (2014-10-13):
>  # See Asia/Ho_Chi_Minh for the source for this data.
> @@ -597,6 +971,32 @@ Zone	Asia/Kashgar	5:03:56	-	LMT	1928     # or Kashi or Kaxgar
>  			5:00	-	+05	1980 May
>  			8:00	PRC	C%sT
>  
> +# peninsular Malaysia
> +# taken from Mok Ly Yng (2003-10-30)
> +# https://web.archive.org/web/20190822231045/http://www.math.nus.edu.sg/~mathelmr/teaching/timezone.html
> +# This agrees with Singapore since 1905-06-01.
> +Zone Asia/Kuala_Lumpur	6:46:46 -	LMT	1901 Jan  1
> +			6:55:25	-	SMT	1905 Jun  1 # Singapore M.T.
> +			7:00	-	+07	1933 Jan  1
> +			7:00	0:20	+0720	1936 Jan  1
> +			7:20	-	+0720	1941 Sep  1
> +			7:30	-	+0730	1942 Feb 16
> +			9:00	-	+09	1945 Sep 12
> +			7:30	-	+0730	1982 Jan  1
> +			8:00	-	+08
> +#
> +# Sabah & Sarawak
> +# From Paul Eggert (2014-08-12):
> +# The data entries here are mostly from Shanks & Pottenger, but the 1942, 1945
> +# and 1982 transition dates are from Mok Ly Yng.
> +Rule	NBorneo	1935	1941	-	Sep	14	0:00	0:20	-
> +Rule	NBorneo	1935	1941	-	Dec	14	0:00	0	-
> +Zone Asia/Kuching	7:21:20	-	LMT	1926 Mar
> +			7:30	-	+0730	1933
> +			8:00 NBorneo  +08/+0820	1942 Feb 16
> +			9:00	-	+09	1945 Sep 12
> +			8:00	-	+08
> +
>  # Kuwait
>  Zone	Asia/Kuwait	3:11:56 -	LMT	1950
>  			3:00	-	+03
> @@ -646,11 +1046,118 @@ Zone	Asia/Phnom_Penh	6:59:40 -	LMT	1906 Jul  1
>  			9:00	-	+09	1945 Sep  2
>  			7:00	-	+07
>  
> +# Saudi Arabia
> +#
> +# From Paul Eggert (2018-08-29):
> +# Time in Saudi Arabia and other countries in the Arabian peninsula was not
> +# standardized until 1968 or so; we don't know exactly when, and possibly it
> +# has never been made official.  Richard P Hunt, in "Islam city yielding to
> +# modern times", New York Times (1961-04-09), p 20, wrote that only airlines
> +# observed standard time, and that people in Jeddah mostly observed quasi-solar
> +# time, doing so by setting their watches at sunrise to 6 o'clock (or to 12
> +# o'clock for "Arab" time).
> +#
> +# Timekeeping differed depending on who you were and which part of Saudi
> +# Arabia you were in.  In 1969, Elias Antar wrote that although a common
> +# practice had been to set one's watch to 12:00 (i.e., midnight) at sunset -
> +# which meant that the time on one side of a mountain could differ greatly from
> +# the time on the other side - many foreigners set their watches to 6pm
> +# instead, while airlines instead used UTC +03 (except in Dhahran, where they
> +# used UTC +04), Aramco used UTC +03 with DST, and the Trans-Arabian Pipe Line
> +# Company used Aramco time in eastern Saudi Arabia and airline time in western.
> +# (The American Military Aid Advisory Group used plain UTC.)  Antar writes,
> +# "A man named Higgins, so the story goes, used to run a local power
> +# station. One day, the whole thing became too much for Higgins and he
> +# assembled his staff and laid down the law. 'I've had enough of this,' he
> +# shrieked. 'It is now 12 o'clock Higgins Time, and from now on this station is
> +# going to run on Higgins Time.' And so, until last year, it did."  See:
> +# Antar E. Dinner at When? Saudi Aramco World, 1969 March/April. 2-3.
> +# http://archive.aramcoworld.com/issue/196902/dinner.at.when.htm
> +# Also see: Antar EN. Arabian flying is confusing.
> +# Port Angeles (WA) Evening News. 1965-03-10. page 3.
> +#
> +# The TZ database cannot represent quasi-solar time; airline time is the best
> +# we can do.  The 1946 foreign air news digest of the U.S. Civil Aeronautics
> +# Board (OCLC 42299995) reported that the "... Arabian Government, inaugurated
> +# a weekly Dhahran-Cairo service, via the Saudi Arabian cities of Riyadh and
> +# Jidda, on March 14, 1947".  Shanks & Pottenger guessed 1950; go with the
> +# earlier date.
> +#
> +# Shanks & Pottenger also state that until 1968-05-01 Saudi Arabia had two
> +# time zones; the other zone, at UT +04, was in the far eastern part of
> +# the country.  Presumably this is documenting airline time.  Ignore this,
> +# as it's before our 1970 cutoff.
> +#
> +Zone	Asia/Riyadh	3:06:52 -	LMT	1947 Mar 14
> +			3:00	-	+03
> +
> +
>  # Israel
>  Zone	Asia/Tel_Aviv	2:19:04 -	LMT	1880
>  			2:21	-	JMT	1918
>  			2:00	Zion	I%sT
>  
> +
> +# Xinjiang
> +
> +# From Luther Ma (2009-11-19):
> +# It seems that Uyghurs in Ürümqi has been using Xinjiang since at least the
> +# 1960's. I know of one Han, now over 50, who grew up in the surrounding
> +# countryside and used Xinjiang time as a child.
> +#
> +# 6. Likewise for Kashgar and the rest of south Xinjiang I don't know of any
> +# start date for Xinjiang time.
> +#
> +# Without having access to local historical records, nor the ability to legally
> +# publish them, I would go with October 1, 1949, when Xinjiang became the Uyghur
> +# Autonomous Region under the PRC. (Before that Uyghurs, of course, would also
> +# not be using Beijing time, but some local time.)
> +
> +# From David Cochrane (2014-03-26):
> +# Just a confirmation that Ürümqi time was implemented in Ürümqi on 1 Feb 1986:
> +# https://content.time.com/time/magazine/article/0,9171,960684,00.html
> +
> +# From Luther Ma (2014-04-22):
> +# I have interviewed numerous people of various nationalities and from
> +# different localities in Xinjiang and can confirm the information in Guo's
> +# report regarding Xinjiang, as well as the Time article reference by David
> +# Cochrane.  Whether officially recognized or not (and both are officially
> +# recognized), two separate times have been in use in Xinjiang since at least
> +# the Cultural Revolution: Xinjiang Time (XJT), aka Ürümqi Time or local time;
> +# and Beijing Time.  There is no confusion in Xinjiang as to which name refers
> +# to which time. Both are widely used in the province, although in some
> +# population groups might be use one to the exclusion of the other.  The only
> +# problem is that computers and smart phones list Ürümqi (or Kashgar) as
> +# having the same time as Beijing.
> +
> +# From Paul Eggert (2014-06-30):
> +# In the early days of the PRC, Tibet was given its own time zone (UT +06)
> +# but this was withdrawn in 1959 and never reinstated; see Tubten Khétsun,
> +# Memories of life in Lhasa under Chinese Rule, Columbia U Press, ISBN
> +# 978-0231142861 (2008), translator's introduction by Matthew Akester, p x.
> +# As this is before our 1970 cutoff, Tibet doesn't need a separate zone.
> +#
> +# Xinjiang Time is well-documented as being officially recognized.  E.g., see
> +# "The Working-Calendar for The Xinjiang Uygur Autonomous Region Government"
> +# <http://www.sinkiang.gov.cn/service/ourworking/> (2014-04-22).
> +# Unfortunately, we have no good records of time in Xinjiang before 1986.
> +# During the 20th century parts of Xinjiang were ruled by the Qing dynasty,
> +# the Republic of China, various warlords, the First and Second East Turkestan
> +# Republics, the Soviet Union, the Kuomintang, and the People's Republic of
> +# China, and tracking down all these organizations' timekeeping rules would be
> +# quite a trick.  Approximate this lost history by a transition from LMT to
> +# UT +06 at the start of 1928, the year of accession of the warlord Jin Shuren,
> +# which happens to be the date given by Shanks & Pottenger (no doubt as a
> +# guess) as the transition from LMT.  Ignore the usage of +08 before
> +# 1986-02-01 under the theory that the transition date to +08 is unknown and
> +# that the sort of users who prefer Etc/GMT-6 now typically ignored the
> +# +08 mandate back then.
> +
> +# Xinjiang time, used by many in western China; represented by Ürümqi / Ürümchi
> +# / Wulumuqi.  (Please use Asia/Shanghai if you prefer Beijing time.)
> +Zone	Asia/Urumqi	5:50:20	-	LMT	1928
> +			6:00	-	+06
> +
>  # Laos
>  # From Paul Eggert (2014-10-11):
>  # See Asia/Ho_Chi_Minh for the source for most of this data.
> @@ -670,6 +1177,68 @@ Zone	Asia/Vientiane	6:50:24 -	LMT	1906 Jul  1
>  # From Whitman:
>  Zone Atlantic/Jan_Mayen	-1:00	-	-01
>  
> +# Iceland
> +#
> +# From Adam David (1993-11-06):
> +# The name of the timezone in Iceland for system / mail / news purposes is GMT.
> +#
> +# (1993-12-05):
> +# This material is paraphrased from the 1988 edition of the University of
> +# Iceland Almanak.
> +#
> +# From January 1st, 1908 the whole of Iceland was standardised at 1 hour
> +# behind GMT. Previously, local mean solar time was used in different parts
> +# of Iceland, the almanak had been based on Reykjavík mean solar time which
> +# was 1 hour and 28 minutes behind GMT.
> +#
> +# "first day of winter" referred to [below] means the first day of the 26 weeks
> +# of winter, according to the old icelandic calendar that dates back to the
> +# time the norsemen first settled Iceland.  The first day of winter is always
> +# Saturday, but is not dependent on the Julian or Gregorian calendars.
> +#
> +# (1993-12-10):
> +# I have a reference from the Oxford Icelandic-English dictionary for the
> +# beginning of winter, which ties it to the ecclesiastical calendar (and thus
> +# to the julian/gregorian calendar) over the period in question.
> +#	the winter begins on the Saturday next before St. Luke's day
> +#	(old style), or on St. Luke's day, if a Saturday.
> +# St. Luke's day ought to be traceable from ecclesiastical sources. "old style"
> +# might be a reference to the Julian calendar as opposed to Gregorian, or it
> +# might mean something else (???).
> +#
> +# From Paul Eggert (2014-11-22):
> +# The information below is taken from the 1988 Almanak; see
> +# http://www.almanak.hi.is/klukkan.html
> +#
> +Rule	Iceland	1917	1919	-	Feb	19	23:00	1:00	-
> +Rule	Iceland	1917	only	-	Oct	21	 1:00	0	-
> +Rule	Iceland	1918	1919	-	Nov	16	 1:00	0	-
> +Rule	Iceland	1921	only	-	Mar	19	23:00	1:00	-
> +Rule	Iceland	1921	only	-	Jun	23	 1:00	0	-
> +Rule	Iceland	1939	only	-	Apr	29	23:00	1:00	-
> +Rule	Iceland	1939	only	-	Oct	29	 2:00	0	-
> +Rule	Iceland	1940	only	-	Feb	25	 2:00	1:00	-
> +Rule	Iceland	1940	1941	-	Nov	Sun>=2	 1:00s	0	-
> +Rule	Iceland	1941	1942	-	Mar	Sun>=2	 1:00s	1:00	-
> +# 1943-1946 - first Sunday in March until first Sunday in winter
> +Rule	Iceland	1943	1946	-	Mar	Sun>=1	 1:00s	1:00	-
> +Rule	Iceland	1942	1948	-	Oct	Sun>=22	 1:00s	0	-
> +# 1947-1967 - first Sunday in April until first Sunday in winter
> +Rule	Iceland	1947	1967	-	Apr	Sun>=1	 1:00s	1:00	-
> +# 1949 and 1967 Oct transitions delayed by 1 week
> +Rule	Iceland	1949	only	-	Oct	30	 1:00s	0	-
> +Rule	Iceland	1950	1966	-	Oct	Sun>=22	 1:00s	0	-
> +Rule	Iceland	1967	only	-	Oct	29	 1:00s	0	-
> +
> +Zone Atlantic/Reykjavik	-1:28	-	LMT	1908
> +			-1:00	Iceland	-01/+00	1968 Apr  7  1:00s
> +			 0:00	-	GMT
> +Link Atlantic/Reykjavik Iceland
> +
> +# South Georgia
> +Zone Atlantic/South_Georgia -2:26:08 -	LMT	1890 # Grytviken
> +			-2:00	-	-02
> +
>  # St Helena
>  Zone Atlantic/St_Helena	-0:22:48 -	LMT	1890 # Jamestown
>  			-0:22:48 -	JMT	1951 # Jamestown Mean Time
> @@ -681,6 +1250,85 @@ Zone Australia/Currie	9:35:28	-	LMT	1895 Sep
>  			10:00	Aus	AE%sT	1968 Oct 15
>  			10:00	AT	AE%sT
>  
> +
> +# Netherlands
> +
> +# Howse writes that the Netherlands' railways used GMT between 1892 and 1940,
> +# but for other purposes the Netherlands used Amsterdam mean time.
> +
> +# However, Robert H. van Gent writes (2001-04-01):
> +# Howse's statement is only correct up to 1909. From 1909-05-01 (00:00:00
> +# Amsterdam mean time) onwards, the whole of the Netherlands (including
> +# the Dutch railways) was required by law to observe Amsterdam mean time
> +# (19 minutes 32.13 seconds ahead of GMT). This had already been the
> +# common practice (except for the railways) for many decades but it was
> +# not until 1909 when the Dutch government finally defined this by law.
> +# On 1937-07-01 this was changed to 20 minutes (exactly) ahead of GMT and
> +# was generally known as Dutch Time ("Nederlandse Tijd").
> +#
> +# (2001-04-08):
> +# 1892-05-01 was the date when the Dutch railways were by law required to
> +# observe GMT while the remainder of the Netherlands adhered to the common
> +# practice of following Amsterdam mean time.
> +#
> +# (2001-04-09):
> +# In 1835 the authorities of the province of North Holland requested the
> +# municipal authorities of the towns and cities in the province to observe
> +# Amsterdam mean time but I do not know in how many cases this request was
> +# actually followed.
> +#
> +# From 1852 onwards the Dutch telegraph offices were by law required to
> +# observe Amsterdam mean time. As the time signals from the observatory of
> +# Leiden were also distributed by the telegraph system, I assume that most
> +# places linked up with the telegraph (and railway) system automatically
> +# adopted Amsterdam mean time.
> +#
> +# Although the early Dutch railway companies initially observed a variety
> +# of times, most of them had adopted Amsterdam mean time by 1858 but it
> +# was not until 1866 when they were all required by law to observe
> +# Amsterdam mean time.
> +
> +# The data entries before 1945 are taken from
> +# https://www.staff.science.uu.nl/~gent0113/wettijd/wettijd.htm
> +
> +# From Paul Eggert (2021-05-09):
> +# I invented the abbreviations AMT for Amsterdam Mean Time and NST for
> +# Netherlands Summer Time, used in the Netherlands from 1835 to 1937.
> +
> +Rule	Neth	1916	only	-	May	 1	0:00	1:00	NST	# Netherlands Summer Time
> +Rule	Neth	1916	only	-	Oct	 1	0:00	0	AMT	# Amsterdam Mean Time
> +Rule	Neth	1917	only	-	Apr	16	2:00s	1:00	NST
> +Rule	Neth	1917	only	-	Sep	17	2:00s	0	AMT
> +Rule	Neth	1918	1921	-	Apr	Mon>=1	2:00s	1:00	NST
> +Rule	Neth	1918	1921	-	Sep	lastMon	2:00s	0	AMT
> +Rule	Neth	1922	only	-	Mar	lastSun	2:00s	1:00	NST
> +Rule	Neth	1922	1936	-	Oct	Sun>=2	2:00s	0	AMT
> +Rule	Neth	1923	only	-	Jun	Fri>=1	2:00s	1:00	NST
> +Rule	Neth	1924	only	-	Mar	lastSun	2:00s	1:00	NST
> +Rule	Neth	1925	only	-	Jun	Fri>=1	2:00s	1:00	NST
> +# From 1926 through 1939 DST began 05-15, except that it was delayed by a week
> +# in years when 05-15 fell in the Pentecost weekend.
> +Rule	Neth	1926	1931	-	May	15	2:00s	1:00	NST
> +Rule	Neth	1932	only	-	May	22	2:00s	1:00	NST
> +Rule	Neth	1933	1936	-	May	15	2:00s	1:00	NST
> +Rule	Neth	1937	only	-	May	22	2:00s	1:00	NST
> +Rule	Neth	1937	only	-	Jul	 1	0:00	1:00	S
> +Rule	Neth	1937	1939	-	Oct	Sun>=2	2:00s	0	-
> +Rule	Neth	1938	1939	-	May	15	2:00s	1:00	S
> +Rule	Neth	1945	only	-	Apr	 2	2:00s	1:00	S
> +Rule	Neth	1945	only	-	Sep	16	2:00s	0	-
> +#
> +# Amsterdam Mean Time was +00:19:32.13, but the .13 is omitted
> +# below because the current format requires STDOFF to be an integer.
> +#
> +Zone Europe/Amsterdam	0:19:32 -	LMT	1835
> +			0:19:32	Neth	%s	1937 Jul  1
> +			0:20	Neth +0020/+0120 1940 May 16  0:00
> +			1:00	C-Eur	CE%sT	1945 Apr  2  2:00
> +			1:00	Neth	CE%sT	1977
> +			1:00	EU	CE%sT
> +
> +
>  # Northern Ireland
>  Zone	Europe/Belfast	-0:23:40 -	LMT	1880 Aug  2
>  			-0:25:21 -	DMT	1916 May 21  2:00
> @@ -692,6 +1340,60 @@ Zone	Europe/Belfast	-0:23:40 -	LMT	1880 Aug  2
>  			 0:00	GB-Eire	%s	1996
>  			 0:00	EU	GMT/BST
>  
> +
> +# Denmark
> +
> +# From Jesper Nørgaard Welen (2005-04-26):
> +# the law [introducing standard time] was in effect from 1894-01-01....
> +# The page https://www.retsinformation.dk/eli/lta/1893/83
> +# confirms this, and states that the law was put forth 1893-03-29.
> +#
> +# The EU [actually, EEC and Euratom] treaty with effect from 1973:
> +# https://www.retsinformation.dk/eli/lta/1972/21100
> +#
> +# This provoked a new law from 1974 to make possible summer time changes
> +# in subsequent decrees with the law
> +# https://www.retsinformation.dk/eli/lta/1974/223
> +#
> +# It seems however that no decree was set forward until 1980.  I have
> +# not found any decree, but in another related law, the effecting DST
> +# changes are stated explicitly to be from 1980-04-06 at 02:00 to
> +# 1980-09-28 at 02:00.  If this is true, this differs slightly from
> +# the EU rule in that DST runs to 02:00, not 03:00.  We don't know
> +# when Denmark began using the EU rule correctly, but we have only
> +# confirmation of the 1980-time, so I presume it was correct in 1981:
> +# The law is about the management of the extra hour, concerning
> +# working hours reported and effect on obligatory-rest rules (which
> +# was suspended on that night):
> +# https://web.archive.org/web/20140104053304/https://www.retsinformation.dk/Forms/R0710.aspx?id=60267
> +
> +# From Jesper Nørgaard Welen (2005-06-11):
> +# The Herning Folkeblad (1980-09-26) reported that the night between
> +# Saturday and Sunday the clock is set back from three to two.
> +
> +# From Paul Eggert (2005-06-11):
> +# Hence the "02:00" of the 1980 law refers to standard time, not
> +# wall-clock time, and so the EU rules were in effect in 1980.
> +
> +Rule	Denmark	1916	only	-	May	14	23:00	1:00	S
> +Rule	Denmark	1916	only	-	Sep	30	23:00	0	-
> +Rule	Denmark	1940	only	-	May	15	 0:00	1:00	S
> +Rule	Denmark	1945	only	-	Apr	 2	 2:00s	1:00	S
> +Rule	Denmark	1945	only	-	Aug	15	 2:00s	0	-
> +Rule	Denmark	1946	only	-	May	 1	 2:00s	1:00	S
> +Rule	Denmark	1946	only	-	Sep	 1	 2:00s	0	-
> +Rule	Denmark	1947	only	-	May	 4	 2:00s	1:00	S
> +Rule	Denmark	1947	only	-	Aug	10	 2:00s	0	-
> +Rule	Denmark	1948	only	-	May	 9	 2:00s	1:00	S
> +Rule	Denmark	1948	only	-	Aug	 8	 2:00s	0	-
> +#
> +Zone Europe/Copenhagen	 0:50:20 -	LMT	1890
> +			 0:50:20 -	CMT	1894 Jan  1 # Copenhagen MT
> +			 1:00	Denmark	CE%sT	1942 Nov  2  2:00s
> +			 1:00	C-Eur	CE%sT	1945 Apr  2  2:00
> +			 1:00	Denmark	CE%sT	1980
> +			 1:00	EU	CE%sT
> +
>  # Guernsey
>  # Data from Joseph S. Myers
>  # https://mm.icann.org/pipermail/tz/2013-September/019883.html
> @@ -747,6 +1449,85 @@ Zone Europe/Ljubljana	0:58:04	-	LMT	1884
>  			1:00	-	CET	1982 Nov 27
>  			1:00	EU	CE%sT
>  
> +
> +# Luxembourg
> +
> +# Whitman disagrees with most of these dates in minor ways;
> +# go with Shanks & Pottenger.
> +Rule	Lux	1916	only	-	May	14	23:00	1:00	S
> +Rule	Lux	1916	only	-	Oct	 1	 1:00	0	-
> +Rule	Lux	1917	only	-	Apr	28	23:00	1:00	S
> +Rule	Lux	1917	only	-	Sep	17	 1:00	0	-
> +Rule	Lux	1918	only	-	Apr	Mon>=15	 2:00s	1:00	S
> +Rule	Lux	1918	only	-	Sep	Mon>=15	 2:00s	0	-
> +Rule	Lux	1919	only	-	Mar	 1	23:00	1:00	S
> +Rule	Lux	1919	only	-	Oct	 5	 3:00	0	-
> +Rule	Lux	1920	only	-	Feb	14	23:00	1:00	S
> +Rule	Lux	1920	only	-	Oct	24	 2:00	0	-
> +Rule	Lux	1921	only	-	Mar	14	23:00	1:00	S
> +Rule	Lux	1921	only	-	Oct	26	 2:00	0	-
> +Rule	Lux	1922	only	-	Mar	25	23:00	1:00	S
> +Rule	Lux	1922	only	-	Oct	Sun>=2	 1:00	0	-
> +Rule	Lux	1923	only	-	Apr	21	23:00	1:00	S
> +Rule	Lux	1923	only	-	Oct	Sun>=2	 2:00	0	-
> +Rule	Lux	1924	only	-	Mar	29	23:00	1:00	S
> +Rule	Lux	1924	1928	-	Oct	Sun>=2	 1:00	0	-
> +Rule	Lux	1925	only	-	Apr	 5	23:00	1:00	S
> +Rule	Lux	1926	only	-	Apr	17	23:00	1:00	S
> +Rule	Lux	1927	only	-	Apr	 9	23:00	1:00	S
> +Rule	Lux	1928	only	-	Apr	14	23:00	1:00	S
> +Rule	Lux	1929	only	-	Apr	20	23:00	1:00	S
> +
> +Zone Europe/Luxembourg	0:24:36 -	LMT	1904 Jun
> +			1:00	Lux	CE%sT	1918 Nov 25
> +			0:00	Lux	WE%sT	1929 Oct  6  2:00s
> +			0:00	Belgium	WE%sT	1940 May 14  3:00
> +			1:00	C-Eur	WE%sT	1944 Sep 18  3:00
> +			1:00	Belgium	CE%sT	1977
> +			1:00	EU	CE%sT
> +
> +# Monaco
> +#
> +# From Michael Deckers (2020-06-12):
> +# In the "Journal de Monaco" of 1892-05-24, online at
> +# https://journaldemonaco.gouv.mc/var/jdm/storage/original/application/b1c67c12c5af11b41ea888fb048e4fe8.pdf
> +# we read: ...
> +#  [In virtue of a Sovereign Ordinance of the May 13 of the current [year],
> +#   legal time in the Principality will be set to, from the date of June 1,
> +#   1892 onwards, to the meridian of Paris, as in France.]
> +# In the "Journal de Monaco" of 1911-03-28, online at
> +# https://journaldemonaco.gouv.mc/var/jdm/storage/original/application/de74ffb7db53d4f599059fe8f0ed482a.pdf
> +# we read an ordinance of 1911-03-16: ...
> +#  [Legal time in the Principality will be set, from the date of promulgation
> +#   of the present ordinance, to legal time in France....  Consequently, legal
> +#   time will be retarded by 9 minutes and 21 seconds.]
> +#
> +Zone	Europe/Monaco	0:29:32 -	LMT	1892 Jun  1
> +			0:09:21	-	PMT	1911 Mar 29 # Paris Mean Time
> +			0:00	France	WE%sT	1945 Sep 16  3:00
> +			1:00	France	CE%sT	1977
> +			1:00	EU	CE%sT
> +
> +
> +# Norway
> +
> +# http://met.no/met/met_lex/q_u/sommertid.html (2004-01) agrees with Shanks &
> +# Pottenger.
> +Rule	Norway	1916	only	-	May	22	1:00	1:00	S
> +Rule	Norway	1916	only	-	Sep	30	0:00	0	-
> +Rule	Norway	1945	only	-	Apr	 2	2:00s	1:00	S
> +Rule	Norway	1945	only	-	Oct	 1	2:00s	0	-
> +Rule	Norway	1959	1964	-	Mar	Sun>=15	2:00s	1:00	S
> +Rule	Norway	1959	1965	-	Sep	Sun>=15	2:00s	0	-
> +Rule	Norway	1965	only	-	Apr	25	2:00s	1:00	S
> +
> +Zone	Europe/Oslo	0:43:00 -	LMT	1895 Jan  1
> +			1:00	Norway	CE%sT	1940 Aug 10 23:00
> +			1:00	C-Eur	CE%sT	1945 Apr  2  2:00
> +			1:00	Norway	CE%sT	1980
> +			1:00	EU	CE%sT
> +Link	Europe/Oslo	Arctic/Longyearbyen
> +
>  # Bosnia and Herzegovina
>  Zone	Europe/Sarajevo	1:13:40	-	LMT	1884
>  			1:00	-	CET	1941 Apr 18 23:00
> @@ -763,6 +1544,64 @@ Zone	Europe/Skopje	1:25:44	-	LMT	1884
>  			1:00	-	CET	1982 Nov 27
>  			1:00	EU	CE%sT
>  
> +
> +# Sweden
> +
> +# From Ivan Nilsson (2001-04-13), superseding Shanks & Pottenger:
> +#
> +# The law "Svensk författningssamling 1878, no 14" about standard time in 1879:
> +# From the beginning of 1879 (that is 01-01 00:00) the time for all
> +# places in the country is "the mean solar time for the meridian at
> +# three degrees, or twelve minutes of time, to the west of the
> +# meridian of the Observatory of Stockholm".  The law is dated 1878-05-31.
> +#
> +# The observatory at that time had the meridian 18° 03' 30"
> +# eastern longitude = 01:12:14 in time.  Less 12 minutes gives the
> +# national standard time as 01:00:14 ahead of GMT....
> +#
> +# About the beginning of CET in Sweden. The lawtext ("Svensk
> +# författningssamling 1899, no 44") states, that "from the beginning
> +# of 1900... ... the same as the mean solar time for the meridian at
> +# the distance of one hour of time from the meridian of the English
> +# observatory at Greenwich, or at 12 minutes 14 seconds to the west
> +# from the meridian of the Observatory of Stockholm". The law is dated
> +# 1899-06-16.  In short: At 1900-01-01 00:00:00 the new standard time
> +# in Sweden is 01:00:00 ahead of GMT.
> +#
> +# 1916: The lawtext ("Svensk författningssamling 1916, no 124") states
> +# that "1916-05-15 is considered to begin one hour earlier". It is
> +# pretty obvious that at 05-14 23:00 the clocks are set to 05-15 00:00....
> +# Further the law says, that "1916-09-30 is considered to end one hour later".
> +#
> +# The laws regulating [DST] are available on the site of the Swedish
> +# Parliament beginning with 1985 - the laws regulating 1980/1984 are
> +# not available on the site (to my knowledge they are only available
> +# in Swedish): <http://www.riksdagen.se/english/work/sfst.asp> (type
> +# "sommartid" without the quotes in the field "Fritext" and then click
> +# the Sök-button).
> +#
> +# (2001-05-13):
> +#
> +# I have now found a newspaper stating that at 1916-10-01 01:00
> +# summertime the church-clocks etc were set back one hour to show
> +# 1916-10-01 00:00 standard time.  The article also reports that some
> +# people thought the switch to standard time would take place already
> +# at 1916-10-01 00:00 summer time, but they had to wait for another
> +# hour before the event took place.
> +#
> +# Source: The newspaper "Dagens Nyheter", 1916-10-01, page 7 upper left.
> +
> +# An extra-special abbreviation style is SET for Swedish Time (svensk
> +# normaltid) 1879-1899, 3° west of the Stockholm Observatory.
> +
> +Zone Europe/Stockholm	1:12:12 -	LMT	1879 Jan  1
> +			1:00:14	-	SET	1900 Jan  1 # Swedish Time
> +			1:00	-	CET	1916 May 14 23:00
> +			1:00	1:00	CEST	1916 Oct  1  1:00
> +			1:00	-	CET	1980
> +			1:00	EU	CE%sT
> +
> +
>  # Moldova / Transnistria
>  Zone	Europe/Tiraspol	1:58:32	-	LMT	1880
>  			1:55	-	CMT	1918 Feb 15 # Chisinau MT
> @@ -793,18 +1632,118 @@ Zone Indian/Antananarivo 3:10:04 -	LMT	1911 Jul
>  			3:00	1:00	EAST	1954 May 29 23:00s
>  			3:00	-	EAT
>  
> +# Christmas
> +Zone Indian/Christmas	7:02:52 -	LMT	1895 Feb
> +			7:00	-	+07
> +
> +# Cocos (Keeling) Is
> +# These islands were ruled by the Ross family from about 1830 to 1978.
> +# We don't know when standard time was introduced; for now, we guess 1900.
> +Zone	Indian/Cocos	6:27:40	-	LMT	1900
> +			6:30	-	+0630
> +
>  # Comoros
>  Zone	Indian/Comoro	2:53:04 -	LMT	1911 Jul # Moroni, Gran Comoro
>  			3:00	-	EAT
>  
> +# Kerguelen
> +Zone Indian/Kerguelen	0	-	-00	1950 # Port-aux-Français
> +			5:00	-	+05
> +
> +# Seychelles
> +#
> +# From P Chan (2020-11-27):
> +# Standard Time was adopted on 1907-01-01.
> +#
> +# Standard Time Ordinance (Chapter 237)
> +# The Laws of Seychelles in Force on the 31st December, 1971, Vol. 6, p 571
> +# https://books.google.com/books?id=efE-AQAAIAAJ&pg=PA571
> +#
> +# From Tim Parenti (2020-12-05):
> +# A footnote on https://books.google.com/books?id=DYdDAQAAMAAJ&pg=PA1689
> +# confirms that Ordinance No. 9 of 1906 "was brought into force on the 1st
> +# January, 1907."
> +
> +Zone	Indian/Mahe	3:41:48 -	LMT	1907 Jan  1 # Victoria
> +			4:00	-	+04
> +# From Paul Eggert (2001-05-30):
> +# Aldabra, Farquhar, and Desroches, originally dependencies of the
> +# Seychelles, were transferred to the British Indian Ocean Territory
> +# in 1965 and returned to Seychelles control in 1976.  We don't know
> +# whether this affected their time zone, so omit this for now.
> +# Possibly the islands were uninhabited.
> +
> +
> +# Maldives
> +Zone	Indian/Maldives	4:54:00 -	LMT	1880 # Malé
> +			4:54:00	-	MMT	1960 # Malé Mean Time
> +			5:00	-	+05
> +
>  # Mayotte
>  Zone	Indian/Mayotte	3:00:56 -	LMT	1911 Jul # Mamoutzou
>  			3:00	-	EAT
>  
> -# US minor outlying islands
> +# Réunion
> +Zone	Indian/Reunion	3:41:52 -	LMT	1911 Jun # Saint-Denis
> +			4:00	-	+04
> +#
> +# Scattered Islands (Îles Éparses) administered from Réunion are as follows.
> +# The following information about them is taken from
> +# Îles Éparses (<http://www.outre-mer.gouv.fr/domtom/ile.htm>, 1997-07-22,
> +# in French; no longer available as of 1999-08-17).
> +# We have no info about their time zone histories.
> +#
> +# Bassas da India - uninhabited
> +# Europa Island - inhabited from 1905 to 1910 by two families
> +# Glorioso Is - inhabited until at least 1958
> +# Juan de Nova - uninhabited
> +# Tromelin - inhabited until at least 1958
> +
> +# Micronesia
> +# Also see commentary for Micronesia in 'australasia'.
> +#
> +# From Paul Eggert (2018-11-18):
> +# Alan Eugene Davis writes (1996-03-16),
> +# "I am certain, having lived there for the past decade, that 'Truk'
> +# (now properly known as Chuuk) ... is in the time zone GMT+10."
> +# Shanks & Pottenger write that Truk switched from UT +10 to +11
> +# on 1978-10-01; ignore this for now.
> +Zone Pacific/Chuuk	-13:52:52 -	LMT	1844 Dec 31
> +			 10:07:08 -	LMT	1901
> +			 10:00	-	+10	1914 Oct
> +			  9:00	-	+09	1919 Feb  1
> +			 10:00	-	+10	1941 Apr  1
> +			  9:00	-	+09	1945 Aug
> +			 10:00	-	+10
> +Link Pacific/Chuuk Pacific/Truk
> +Link Pacific/Chuuk Pacific/Yap
> +
> +# Tuvalu
> +Zone Pacific/Funafuti	11:56:52 -	LMT	1901
> +			12:00	-	+12
> +
> +# Gambier Islands
> +Zone	Pacific/Gambier	 -8:59:48 -	LMT	1912 Oct # Rikitea
> +			 -9:00	-	-09
> +
> +# Solomon Islands
> +Zone Pacific/Guadalcanal 10:39:48 -	LMT	1912 Oct # Honiara
> +			11:00	-	+11
> +
> +# Johnston
>  Zone Pacific/Johnston	-10:00	-	HST
>  
> -# US minor outlying islands
> +# Marshall Is
> +Zone Pacific/Majuro	 11:24:48 -	LMT	1901
> +			 11:00	-	+11	1914 Oct
> +			  9:00	-	+09	1919 Feb  1
> +			 11:00	-	+11	1937
> +			 10:00	-	+10	1941 Apr  1
> +			  9:00	-	+09	1944 Jan 30
> +			 11:00	-	+11	1969 Oct
> +			 12:00	-	+12
> +
> +# Midway
>  #
>  # From Mark Brader (2005-01-23):
>  # [Fallacies and Fantasies of Air Transport History, by R.E.G. Davies,
> @@ -821,9 +1760,71 @@ Zone Pacific/Midway	-11:49:28 -	LMT	1901
>  			-11:00	1:00	-10	1956 Sep  2
>  			-11:00	-	-11
>  
> +# Palau (Belau)
> +# See commentary for Micronesia in 'australasia'.
> +Zone Pacific/Palau	-15:02:04 -	LMT	1844 Dec 31	# Koror
> +			  8:57:56 -	LMT	1901
> +			  9:00	-	+09
> +
> +# Micronesia
> +# See commentary for Micronesia in 'australasia'.
> +Zone Pacific/Pohnpei	-13:27:08 -	LMT	1844 Dec 31	# Kolonia
> +			 10:32:52 -	LMT	1901
> +			 11:00	-	+11	1914 Oct
> +			  9:00	-	+09	1919 Feb  1
> +			 11:00	-	+11	1937
> +			 10:00	-	+10	1941 Apr  1
> +			  9:00	-	+09	1945 Aug
> +			 11:00	-	+11
> +Link Pacific/Pohnpei Pacific/Ponape
> +
> +# Papua New Guinea
> +Zone Pacific/Port_Moresby 9:48:40 -	LMT	1880
> +			9:48:32	-	PMMT	1895 # Port Moresby Mean Time
> +			10:00	-	+10
> +
>  # N Mariana Is
>  Zone Pacific/Saipan	-14:17:00 -	LMT	1844 Dec 31
>  			 9:43:00 -	LMT	1901
>  			 9:00	-	+09	1969 Oct
>  			10:00	-	+10	2000 Dec 23
>  			10:00	-	ChST	# Chamorro Standard Time
> +
> +# Society Islands
> +Zone	Pacific/Tahiti	 -9:58:16 -	LMT	1912 Oct # Papeete
> +			-10:00	-	-10
> +
> +# Gilbert Islands
> +Zone Pacific/Tarawa	 11:32:04 -	LMT	1901 # Bairiki
> +			 12:00	-	+12
> +
> +
> +# Wake
> +
> +# From Vernice Anderson, Personal Secretary to Philip Jessup,
> +# US Ambassador At Large (oral history interview, 1971-02-02):
> +#
> +# Saturday, the 14th [of October, 1950] - ...  The time was all the
> +# more confusing at that point, because we had crossed the
> +# International Date Line, thus getting two Sundays.  Furthermore, we
> +# discovered that Wake Island had two hours of daylight saving time
> +# making calculation of time in Washington difficult if not almost
> +# impossible.
> +#
> +# https://www.trumanlibrary.org/oralhist/andrsonv.htm
> +
> +# From Paul Eggert (2003-03-23):
> +# We have no other report of DST in Wake Island, so omit this info for now.
> +
> +# Also see commentary for Micronesia in 'australasia'.
> +Zone	Pacific/Wake	11:06:28 -	LMT	1901
> +			12:00	-	+12
> +
> +
> +# Wallis and Futuna
> +Zone	Pacific/Wallis	12:15:20 -	LMT	1901
> +			12:00	-	+12
> +
> +# Local Variables:
> +# coding: utf-8
> +# End:
> diff --git a/checktab.awk b/checktab.awk
> index d5317ac..5748341 100644
> --- a/checktab.awk
> +++ b/checktab.awk
> @@ -147,7 +147,7 @@ $1 ~ /^#/ { next }
>  		ruleUsed[$2] = 1
>  		if ($3 ~ /%/) rulePercentUsed[$2] = 1
>  	}
> -	if (tz && tz ~ /\//) {
> +	if (tz && tz ~ /\// && tz !~ /^Etc\//) {
>  		if (!tztab[tz]) {
>  			printf "%s: no data for '%s'\n", zone_table, tz \
>  				>>"/dev/stderr"
> @@ -171,7 +171,7 @@ END {
>  		}
>  	}
>  	for (tz in tztab) {
> -		if (!zoneSeen[tz]) {
> +		if (!zoneSeen[tz] && tz !~ /^Etc\//) {
>  			printf "%s:%d: no Zone table for '%s'\n", \
>  				zone_table, tz2NR[tz], tz >>"/dev/stderr"
>  			status = 1
> diff --git a/etcetera b/etcetera
> index 1dc7411..dc21c4d 100644
> --- a/etcetera
> +++ b/etcetera
> @@ -12,6 +12,8 @@
>  # Starting with POSIX 1003.1-2001, the entries below are all
>  # unnecessary as settings for the TZ environment variable.  E.g.,
>  # instead of TZ='Etc/GMT+4' one can use the POSIX setting TZ='<-04>+4'.
> +# However, some entries are needed if 'backward' is used:
> +# for example, the 'backward' file links Etc/GMT to Africa/Abidjan.
>  #
>  # Do not use a POSIX TZ setting like TZ='GMT+4', which is four hours
>  # behind GMT but uses the completely misleading abbreviation "GMT".
> diff --git a/europe b/europe
> index 9e73fa9..b9289d3 100644
> --- a/europe
> +++ b/europe
> @@ -68,7 +68,6 @@
>  #        0:00       GMT  BST  BDST  Greenwich, British Summer
>  #        0:00       GMT  IST        Greenwich, Irish Summer
>  #        0:00       WET  WEST WEMT  Western Europe
> -#        0:19:32.13 AMT* NST*       Amsterdam, Netherlands Summer (1835-1937)
>  #        1:00       BST             British Standard (1968-1971)
>  #        1:00       IST  GMT        Irish Standard (1968-) with winter DST
>  #        1:00       CET  CEST CEMT  Central Europe
> @@ -1024,59 +1023,8 @@ Zone	Europe/Prague	0:57:44 -	LMT	1850
>  # Use Europe/Prague also for Slovakia.
>  
>  # Denmark, Faroe Islands, and Greenland
> +# For Denmark see Europe/Berlin.
>  
> -# From Jesper Nørgaard Welen (2005-04-26):
> -# the law [introducing standard time] was in effect from 1894-01-01....
> -# The page https://www.retsinformation.dk/eli/lta/1893/83
> -# confirms this, and states that the law was put forth 1893-03-29.
> -#
> -# The EU [actually, EEC and Euratom] treaty with effect from 1973:
> -# https://www.retsinformation.dk/eli/lta/1972/21100
> -#
> -# This provoked a new law from 1974 to make possible summer time changes
> -# in subsequent decrees with the law
> -# https://www.retsinformation.dk/eli/lta/1974/223
> -#
> -# It seems however that no decree was set forward until 1980.  I have
> -# not found any decree, but in another related law, the effecting DST
> -# changes are stated explicitly to be from 1980-04-06 at 02:00 to
> -# 1980-09-28 at 02:00.  If this is true, this differs slightly from
> -# the EU rule in that DST runs to 02:00, not 03:00.  We don't know
> -# when Denmark began using the EU rule correctly, but we have only
> -# confirmation of the 1980-time, so I presume it was correct in 1981:
> -# The law is about the management of the extra hour, concerning
> -# working hours reported and effect on obligatory-rest rules (which
> -# was suspended on that night):
> -# https://web.archive.org/web/20140104053304/https://www.retsinformation.dk/Forms/R0710.aspx?id=60267
> -
> -# From Jesper Nørgaard Welen (2005-06-11):
> -# The Herning Folkeblad (1980-09-26) reported that the night between
> -# Saturday and Sunday the clock is set back from three to two.
> -
> -# From Paul Eggert (2005-06-11):
> -# Hence the "02:00" of the 1980 law refers to standard time, not
> -# wall-clock time, and so the EU rules were in effect in 1980.
> -
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
> -Rule	Denmark	1916	only	-	May	14	23:00	1:00	S
> -Rule	Denmark	1916	only	-	Sep	30	23:00	0	-
> -Rule	Denmark	1940	only	-	May	15	 0:00	1:00	S
> -Rule	Denmark	1945	only	-	Apr	 2	 2:00s	1:00	S
> -Rule	Denmark	1945	only	-	Aug	15	 2:00s	0	-
> -Rule	Denmark	1946	only	-	May	 1	 2:00s	1:00	S
> -Rule	Denmark	1946	only	-	Sep	 1	 2:00s	0	-
> -Rule	Denmark	1947	only	-	May	 4	 2:00s	1:00	S
> -Rule	Denmark	1947	only	-	Aug	10	 2:00s	0	-
> -Rule	Denmark	1948	only	-	May	 9	 2:00s	1:00	S
> -Rule	Denmark	1948	only	-	Aug	 8	 2:00s	0	-
> -#
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Europe/Copenhagen	 0:50:20 -	LMT	1890
> -			 0:50:20 -	CMT	1894 Jan  1 # Copenhagen MT
> -			 1:00	Denmark	CE%sT	1942 Nov  2  2:00s
> -			 1:00	C-Eur	CE%sT	1945 Apr  2  2:00
> -			 1:00	Denmark	CE%sT	1980
> -			 1:00	EU	CE%sT
>  Zone Atlantic/Faroe	-0:27:04 -	LMT	1908 Jan 11 # Tórshavn
>  			 0:00	-	WET	1981
>  			 0:00	EU	WE%sT
> @@ -1621,62 +1569,7 @@ Zone	Europe/Budapest	1:16:20 -	LMT	1890 Nov  1
>  			1:00	EU	CE%sT
>  
>  # Iceland
> -#
> -# From Adam David (1993-11-06):
> -# The name of the timezone in Iceland for system / mail / news purposes is GMT.
> -#
> -# (1993-12-05):
> -# This material is paraphrased from the 1988 edition of the University of
> -# Iceland Almanak.
> -#
> -# From January 1st, 1908 the whole of Iceland was standardised at 1 hour
> -# behind GMT. Previously, local mean solar time was used in different parts
> -# of Iceland, the almanak had been based on Reykjavík mean solar time which
> -# was 1 hour and 28 minutes behind GMT.
> -#
> -# "first day of winter" referred to [below] means the first day of the 26 weeks
> -# of winter, according to the old icelandic calendar that dates back to the
> -# time the norsemen first settled Iceland.  The first day of winter is always
> -# Saturday, but is not dependent on the Julian or Gregorian calendars.
> -#
> -# (1993-12-10):
> -# I have a reference from the Oxford Icelandic-English dictionary for the
> -# beginning of winter, which ties it to the ecclesiastical calendar (and thus
> -# to the julian/gregorian calendar) over the period in question.
> -#	the winter begins on the Saturday next before St. Luke's day
> -#	(old style), or on St. Luke's day, if a Saturday.
> -# St. Luke's day ought to be traceable from ecclesiastical sources. "old style"
> -# might be a reference to the Julian calendar as opposed to Gregorian, or it
> -# might mean something else (???).
> -#
> -# From Paul Eggert (2014-11-22):
> -# The information below is taken from the 1988 Almanak; see
> -# http://www.almanak.hi.is/klukkan.html
> -#
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
> -Rule	Iceland	1917	1919	-	Feb	19	23:00	1:00	-
> -Rule	Iceland	1917	only	-	Oct	21	 1:00	0	-
> -Rule	Iceland	1918	1919	-	Nov	16	 1:00	0	-
> -Rule	Iceland	1921	only	-	Mar	19	23:00	1:00	-
> -Rule	Iceland	1921	only	-	Jun	23	 1:00	0	-
> -Rule	Iceland	1939	only	-	Apr	29	23:00	1:00	-
> -Rule	Iceland	1939	only	-	Oct	29	 2:00	0	-
> -Rule	Iceland	1940	only	-	Feb	25	 2:00	1:00	-
> -Rule	Iceland	1940	1941	-	Nov	Sun>=2	 1:00s	0	-
> -Rule	Iceland	1941	1942	-	Mar	Sun>=2	 1:00s	1:00	-
> -# 1943-1946 - first Sunday in March until first Sunday in winter
> -Rule	Iceland	1943	1946	-	Mar	Sun>=1	 1:00s	1:00	-
> -Rule	Iceland	1942	1948	-	Oct	Sun>=22	 1:00s	0	-
> -# 1947-1967 - first Sunday in April until first Sunday in winter
> -Rule	Iceland	1947	1967	-	Apr	Sun>=1	 1:00s	1:00	-
> -# 1949 and 1967 Oct transitions delayed by 1 week
> -Rule	Iceland	1949	only	-	Oct	30	 1:00s	0	-
> -Rule	Iceland	1950	1966	-	Oct	Sun>=22	 1:00s	0	-
> -Rule	Iceland	1967	only	-	Oct	29	 1:00s	0	-
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Atlantic/Reykjavik	-1:28	-	LMT	1908
> -			-1:00	Iceland	-01/+00	1968 Apr  7  1:00s
> -			 0:00	-	GMT
> +# See Etc/GMT.
>  
>  # Italy
>  #
> @@ -1947,40 +1840,7 @@ Zone	Europe/Vilnius	1:41:16	-	LMT	1880
>  			2:00	EU	EE%sT
>  
>  # Luxembourg
> -# Whitman disagrees with most of these dates in minor ways;
> -# go with Shanks & Pottenger.
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
> -Rule	Lux	1916	only	-	May	14	23:00	1:00	S
> -Rule	Lux	1916	only	-	Oct	 1	 1:00	0	-
> -Rule	Lux	1917	only	-	Apr	28	23:00	1:00	S
> -Rule	Lux	1917	only	-	Sep	17	 1:00	0	-
> -Rule	Lux	1918	only	-	Apr	Mon>=15	 2:00s	1:00	S
> -Rule	Lux	1918	only	-	Sep	Mon>=15	 2:00s	0	-
> -Rule	Lux	1919	only	-	Mar	 1	23:00	1:00	S
> -Rule	Lux	1919	only	-	Oct	 5	 3:00	0	-
> -Rule	Lux	1920	only	-	Feb	14	23:00	1:00	S
> -Rule	Lux	1920	only	-	Oct	24	 2:00	0	-
> -Rule	Lux	1921	only	-	Mar	14	23:00	1:00	S
> -Rule	Lux	1921	only	-	Oct	26	 2:00	0	-
> -Rule	Lux	1922	only	-	Mar	25	23:00	1:00	S
> -Rule	Lux	1922	only	-	Oct	Sun>=2	 1:00	0	-
> -Rule	Lux	1923	only	-	Apr	21	23:00	1:00	S
> -Rule	Lux	1923	only	-	Oct	Sun>=2	 2:00	0	-
> -Rule	Lux	1924	only	-	Mar	29	23:00	1:00	S
> -Rule	Lux	1924	1928	-	Oct	Sun>=2	 1:00	0	-
> -Rule	Lux	1925	only	-	Apr	 5	23:00	1:00	S
> -Rule	Lux	1926	only	-	Apr	17	23:00	1:00	S
> -Rule	Lux	1927	only	-	Apr	 9	23:00	1:00	S
> -Rule	Lux	1928	only	-	Apr	14	23:00	1:00	S
> -Rule	Lux	1929	only	-	Apr	20	23:00	1:00	S
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Europe/Luxembourg	0:24:36 -	LMT	1904 Jun
> -			1:00	Lux	CE%sT	1918 Nov 25
> -			0:00	Lux	WE%sT	1929 Oct  6  2:00s
> -			0:00	Belgium	WE%sT	1940 May 14  3:00
> -			1:00	C-Eur	WE%sT	1944 Sep 18  3:00
> -			1:00	Belgium	CE%sT	1977
> -			1:00	EU	CE%sT
> +# See Europe/Brussels.
>  
>  # North Macedonia
>  # See Europe/Belgrade.
> @@ -2081,122 +1941,16 @@ Zone	Europe/Chisinau	1:55:20 -	LMT	1880
>  			2:00	Moldova	EE%sT
>  
>  # Monaco
> -#
> -# From Michael Deckers (2020-06-12):
> -# In the "Journal de Monaco" of 1892-05-24, online at
> -# https://journaldemonaco.gouv.mc/var/jdm/storage/original/application/b1c67c12c5af11b41ea888fb048e4fe8.pdf
> -# we read: ...
> -#  [In virtue of a Sovereign Ordinance of the May 13 of the current [year],
> -#   legal time in the Principality will be set to, from the date of June 1,
> -#   1892 onwards, to the meridian of Paris, as in France.]
> -# In the "Journal de Monaco" of 1911-03-28, online at
> -# https://journaldemonaco.gouv.mc/var/jdm/storage/original/application/de74ffb7db53d4f599059fe8f0ed482a.pdf
> -# we read an ordinance of 1911-03-16: ...
> -#  [Legal time in the Principality will be set, from the date of promulgation
> -#   of the present ordinance, to legal time in France....  Consequently, legal
> -#   time will be retarded by 9 minutes and 21 seconds.]
> -#
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Europe/Monaco	0:29:32 -	LMT	1892 Jun  1
> -			0:09:21	-	PMT	1911 Mar 29 # Paris Mean Time
> -			0:00	France	WE%sT	1945 Sep 16  3:00
> -			1:00	France	CE%sT	1977
> -			1:00	EU	CE%sT
> +# See Europe/Paris.
>  
>  # Montenegro
>  # See Europe/Belgrade.
>  
>  # Netherlands
> -
> -# Howse writes that the Netherlands' railways used GMT between 1892 and 1940,
> -# but for other purposes the Netherlands used Amsterdam mean time.
> -
> -# However, Robert H. van Gent writes (2001-04-01):
> -# Howse's statement is only correct up to 1909. From 1909-05-01 (00:00:00
> -# Amsterdam mean time) onwards, the whole of the Netherlands (including
> -# the Dutch railways) was required by law to observe Amsterdam mean time
> -# (19 minutes 32.13 seconds ahead of GMT). This had already been the
> -# common practice (except for the railways) for many decades but it was
> -# not until 1909 when the Dutch government finally defined this by law.
> -# On 1937-07-01 this was changed to 20 minutes (exactly) ahead of GMT and
> -# was generally known as Dutch Time ("Nederlandse Tijd").
> -#
> -# (2001-04-08):
> -# 1892-05-01 was the date when the Dutch railways were by law required to
> -# observe GMT while the remainder of the Netherlands adhered to the common
> -# practice of following Amsterdam mean time.
> -#
> -# (2001-04-09):
> -# In 1835 the authorities of the province of North Holland requested the
> -# municipal authorities of the towns and cities in the province to observe
> -# Amsterdam mean time but I do not know in how many cases this request was
> -# actually followed.
> -#
> -# From 1852 onwards the Dutch telegraph offices were by law required to
> -# observe Amsterdam mean time. As the time signals from the observatory of
> -# Leiden were also distributed by the telegraph system, I assume that most
> -# places linked up with the telegraph (and railway) system automatically
> -# adopted Amsterdam mean time.
> -#
> -# Although the early Dutch railway companies initially observed a variety
> -# of times, most of them had adopted Amsterdam mean time by 1858 but it
> -# was not until 1866 when they were all required by law to observe
> -# Amsterdam mean time.
> -
> -# The data entries before 1945 are taken from
> -# https://www.staff.science.uu.nl/~gent0113/wettijd/wettijd.htm
> -
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
> -Rule	Neth	1916	only	-	May	 1	0:00	1:00	NST	# Netherlands Summer Time
> -Rule	Neth	1916	only	-	Oct	 1	0:00	0	AMT	# Amsterdam Mean Time
> -Rule	Neth	1917	only	-	Apr	16	2:00s	1:00	NST
> -Rule	Neth	1917	only	-	Sep	17	2:00s	0	AMT
> -Rule	Neth	1918	1921	-	Apr	Mon>=1	2:00s	1:00	NST
> -Rule	Neth	1918	1921	-	Sep	lastMon	2:00s	0	AMT
> -Rule	Neth	1922	only	-	Mar	lastSun	2:00s	1:00	NST
> -Rule	Neth	1922	1936	-	Oct	Sun>=2	2:00s	0	AMT
> -Rule	Neth	1923	only	-	Jun	Fri>=1	2:00s	1:00	NST
> -Rule	Neth	1924	only	-	Mar	lastSun	2:00s	1:00	NST
> -Rule	Neth	1925	only	-	Jun	Fri>=1	2:00s	1:00	NST
> -# From 1926 through 1939 DST began 05-15, except that it was delayed by a week
> -# in years when 05-15 fell in the Pentecost weekend.
> -Rule	Neth	1926	1931	-	May	15	2:00s	1:00	NST
> -Rule	Neth	1932	only	-	May	22	2:00s	1:00	NST
> -Rule	Neth	1933	1936	-	May	15	2:00s	1:00	NST
> -Rule	Neth	1937	only	-	May	22	2:00s	1:00	NST
> -Rule	Neth	1937	only	-	Jul	 1	0:00	1:00	S
> -Rule	Neth	1937	1939	-	Oct	Sun>=2	2:00s	0	-
> -Rule	Neth	1938	1939	-	May	15	2:00s	1:00	S
> -Rule	Neth	1945	only	-	Apr	 2	2:00s	1:00	S
> -Rule	Neth	1945	only	-	Sep	16	2:00s	0	-
> -#
> -# Amsterdam Mean Time was +00:19:32.13, but the .13 is omitted
> -# below because the current format requires STDOFF to be an integer.
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Europe/Amsterdam	0:19:32 -	LMT	1835
> -			0:19:32	Neth	%s	1937 Jul  1
> -			0:20	Neth +0020/+0120 1940 May 16  0:00
> -			1:00	C-Eur	CE%sT	1945 Apr  2  2:00
> -			1:00	Neth	CE%sT	1977
> -			1:00	EU	CE%sT
> +# See Europe/Brussels.
>  
>  # Norway
> -# http://met.no/met/met_lex/q_u/sommertid.html (2004-01) agrees with Shanks &
> -# Pottenger.
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
> -Rule	Norway	1916	only	-	May	22	1:00	1:00	S
> -Rule	Norway	1916	only	-	Sep	30	0:00	0	-
> -Rule	Norway	1945	only	-	Apr	 2	2:00s	1:00	S
> -Rule	Norway	1945	only	-	Oct	 1	2:00s	0	-
> -Rule	Norway	1959	1964	-	Mar	Sun>=15	2:00s	1:00	S
> -Rule	Norway	1959	1965	-	Sep	Sun>=15	2:00s	0	-
> -Rule	Norway	1965	only	-	Apr	25	2:00s	1:00	S
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	Europe/Oslo	0:43:00 -	LMT	1895 Jan  1
> -			1:00	Norway	CE%sT	1940 Aug 10 23:00
> -			1:00	C-Eur	CE%sT	1945 Apr  2  2:00
> -			1:00	Norway	CE%sT	1980
> -			1:00	EU	CE%sT
> +# See Europe/Berlin.
>  
>  # Svalbard & Jan Mayen
>  
> @@ -2243,7 +1997,7 @@ Zone	Europe/Oslo	0:43:00 -	LMT	1895 Jan  1
>  # the German armed forces at the Svalbard weather station code-named
>  # Haudegen did not surrender to the Allies until September 1945.
>  #
> -# All these events predate our cutoff date of 1970, so use Europe/Oslo
> +# All these events predate our cutoff date of 1970, so use Europe/Berlin
>  # for these regions.
>  
>  
> @@ -3627,58 +3381,7 @@ Zone	Atlantic/Canary	-1:01:36 -	LMT	1922 Mar # Las Palmas de Gran C.
>  # Ignore this for now, as the Canaries are part of the EU.
>  
>  # Sweden
> -
> -# From Ivan Nilsson (2001-04-13), superseding Shanks & Pottenger:
> -#
> -# The law "Svensk författningssamling 1878, no 14" about standard time in 1879:
> -# From the beginning of 1879 (that is 01-01 00:00) the time for all
> -# places in the country is "the mean solar time for the meridian at
> -# three degrees, or twelve minutes of time, to the west of the
> -# meridian of the Observatory of Stockholm".  The law is dated 1878-05-31.
> -#
> -# The observatory at that time had the meridian 18° 03' 30"
> -# eastern longitude = 01:12:14 in time.  Less 12 minutes gives the
> -# national standard time as 01:00:14 ahead of GMT....
> -#
> -# About the beginning of CET in Sweden. The lawtext ("Svensk
> -# författningssamling 1899, no 44") states, that "from the beginning
> -# of 1900... ... the same as the mean solar time for the meridian at
> -# the distance of one hour of time from the meridian of the English
> -# observatory at Greenwich, or at 12 minutes 14 seconds to the west
> -# from the meridian of the Observatory of Stockholm". The law is dated
> -# 1899-06-16.  In short: At 1900-01-01 00:00:00 the new standard time
> -# in Sweden is 01:00:00 ahead of GMT.
> -#
> -# 1916: The lawtext ("Svensk författningssamling 1916, no 124") states
> -# that "1916-05-15 is considered to begin one hour earlier". It is
> -# pretty obvious that at 05-14 23:00 the clocks are set to 05-15 00:00....
> -# Further the law says, that "1916-09-30 is considered to end one hour later".
> -#
> -# The laws regulating [DST] are available on the site of the Swedish
> -# Parliament beginning with 1985 - the laws regulating 1980/1984 are
> -# not available on the site (to my knowledge they are only available
> -# in Swedish): <http://www.riksdagen.se/english/work/sfst.asp> (type
> -# "sommartid" without the quotes in the field "Fritext" and then click
> -# the Sök-button).
> -#
> -# (2001-05-13):
> -#
> -# I have now found a newspaper stating that at 1916-10-01 01:00
> -# summertime the church-clocks etc were set back one hour to show
> -# 1916-10-01 00:00 standard time.  The article also reports that some
> -# people thought the switch to standard time would take place already
> -# at 1916-10-01 00:00 summer time, but they had to wait for another
> -# hour before the event took place.
> -#
> -# Source: The newspaper "Dagens Nyheter", 1916-10-01, page 7 upper left.
> -
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Europe/Stockholm	1:12:12 -	LMT	1879 Jan  1
> -			1:00:14	-	SET	1900 Jan  1 # Swedish Time
> -			1:00	-	CET	1916 May 14 23:00
> -			1:00	1:00	CEST	1916 Oct  1  1:00
> -			1:00	-	CET	1980
> -			1:00	EU	CE%sT
> +# See Europe/Berlin.
>  
>  # Switzerland
>  # From Howse:
> diff --git a/northamerica b/northamerica
> index b27311a..7edd8ef 100644
> --- a/northamerica
> +++ b/northamerica
> @@ -1593,24 +1593,7 @@ Zone America/Moncton	-4:19:08 -	LMT	1883 Dec  9
>  # From Paul Eggert (2020-01-10):
>  # See America/Toronto for most of Quebec, including Montreal.
>  # See America/Halifax for the ÃŽles de la Madeleine and the Listuguj reserve.
> -#
> -# Matthews and Vincent (1998) also write that Quebec east of the -63
> -# meridian is supposed to observe AST, but residents as far east as
> -# Natashquan use EST/EDT, and residents east of Natashquan use AST.
> -# The Quebec department of justice writes in
> -# "The situation in Minganie and Basse-Côte-Nord"
> -# https://www.justice.gouv.qc.ca/en/department/ministre/functions-and-responsabilities/legal-time-in-quebec/the-situation-in-minganie-and-basse-cote-nord/
> -# that the coastal strip from just east of Natashquan to Blanc-Sablon
> -# observes Atlantic standard time all year round.
> -# This common practice was codified into law as of 2007; see Legal Time Act,
> -# CQLR c T-5.1 <http://legisquebec.gouv.qc.ca/en/ShowDoc/cs/T-5.1>.
> -# For lack of better info, guess this practice began around 1970, contra to
> -# Shanks & Pottenger who have this region observing AST/ADT.
> -
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone America/Blanc-Sablon -3:48:28 -	LMT	1884
> -			-4:00	Canada	A%sT	1970
> -			-4:00	-	AST
> +# See America/Puerto_Rico for east of Natashquan.
>  
>  # Ontario
>  
> @@ -1649,54 +1632,6 @@ Zone America/Blanc-Sablon -3:48:28 -	LMT	1884
>  # time became a comic failure in Orillia. Toronto Star 2017-07-08.
>  # https://www.thestar.com/news/insight/2017/07/08/bold-attempt-at-daylight-saving-time-became-a-comic-failure-in-orillia.html
>  
> -# From Paul Eggert (1997-10-17):
> -# Mark Brader writes that an article in the 1997-10-14 Toronto Star
> -# says that Atikokan, Ontario currently does not observe DST,
> -# but will vote on 11-10 whether to use EST/EDT.
> -# He also writes that the Ontario Time Act (1990, Chapter T.9)
> -# http://www.gov.on.ca/MBS/english/publications/statregs/conttext.html
> -# says that Ontario east of 90W uses EST/EDT, and west of 90W uses CST/CDT.
> -# Officially Atikokan is therefore on CST/CDT, and most likely this report
> -# concerns a non-official time observed as a matter of local practice.
> -#
> -# From Paul Eggert (2000-10-02):
> -# Matthews and Vincent (1998) write that Atikokan, Pickle Lake, and
> -# New Osnaburgh observe CST all year, that Big Trout Lake observes
> -# CST/CDT, and that Upsala and Shebandowan observe EST/EDT, all in
> -# violation of the official Ontario rules.
> -#
> -# From Paul Eggert (2006-07-09):
> -# Chris Walton (2006-07-06) mentioned an article by Stephanie MacLellan in the
> -# 2005-07-21 Chronicle-Journal, which said:
> -#
> -#	The clocks in Atikokan stay set on standard time year-round.
> -#	This means they spend about half the time on central time and
> -#	the other half on eastern time.
> -#
> -#	For the most part, the system works, Mayor Dennis Brown said.
> -#
> -#	"The majority of businesses in Atikokan deal more with Eastern
> -#	Canada, but there are some that deal with Western Canada," he
> -#	said.  "I don't see any changes happening here."
> -#
> -# Walton also writes "Supposedly Pickle Lake and Mishkeegogamang
> -# [New Osnaburgh] follow the same practice."
> -
> -# From Garry McKinnon (2006-07-14) via Chris Walton:
> -# I chatted with a member of my board who has an outstanding memory
> -# and a long history in Atikokan (and in the telecom industry) and he
> -# can say for certain that Atikokan has been practicing the current
> -# time keeping since 1952, at least.
> -
> -# From Paul Eggert (2006-07-17):
> -# Shanks & Pottenger say that Atikokan has agreed with Rainy River
> -# ever since standard time was introduced, but the information from
> -# McKinnon sounds more authoritative.  For now, assume that Atikokan
> -# switched to EST immediately after WWII era daylight saving time
> -# ended.  This matches the old (less-populous) America/Coral_Harbour
> -# entry since our cutoff date of 1970, so we can move
> -# America/Coral_Harbour to the 'backward' file.
> -
>  # From Mark Brader (2010-03-06):
>  #
>  # Currently the database has:
> @@ -1842,11 +1777,7 @@ Zone America/Rainy_River -6:18:16 -	LMT	1895
>  			-6:00	Canada	C%sT	1940 Sep 29
>  			-6:00	1:00	CDT	1942 Feb  9  2:00s
>  			-6:00	Canada	C%sT
> -Zone America/Atikokan	-6:06:28 -	LMT	1895
> -			-6:00	Canada	C%sT	1940 Sep 29
> -			-6:00	1:00	CDT	1942 Feb  9  2:00s
> -			-6:00	Canada	C%sT	1945 Sep 30  2:00
> -			-5:00	-	EST
> +# For Atikokan see America/Panama.
>  
>  
>  # Manitoba
> @@ -2037,60 +1968,6 @@ Zone America/Edmonton	-7:33:52 -	LMT	1906 Sep
>  # Shanks & Pottenger write that since 1970 most of this region has
>  # been like Vancouver.
>  # Dawson Creek uses MST.  Much of east BC is like Edmonton.
> -# Matthews and Vincent (1998) write that Creston is like Dawson Creek.
> -
> -# It seems though that (re: Creston) is not entirely correct:
> -
> -# From Chris Walton (2011-12-01):
> -# There are two areas within the Canadian province of British Columbia
> -# that do not currently observe daylight saving:
> -# a) The Creston Valley (includes the town of Creston and surrounding area)
> -# b) The eastern half of the Peace River Regional District
> -# (includes the cities of Dawson Creek and Fort St. John)
> -
> -# Earlier this year I stumbled across a detailed article about the time
> -# keeping history of Creston; it was written by Tammy Hardwick who is the
> -# manager of the Creston & District Museum. The article was written in May 2009.
> -# http://www.ilovecreston.com/?p=articles&t=spec&ar=260
> -# According to the article, Creston has not changed its clocks since June 1918.
> -# i.e. Creston has been stuck on UT-7 for 93 years.
> -# Dawson Creek, on the other hand, changed its clocks as recently as April 1972.
> -
> -# Unfortunately the exact date for the time change in June 1918 remains
> -# unknown and will be difficult to ascertain.  I e-mailed Tammy a few months
> -# ago to ask if Sunday June 2 was a reasonable guess.  She said it was just
> -# as plausible as any other date (in June).  She also said that after writing
> -# the article she had discovered another time change in 1916; this is the
> -# subject of another article which she wrote in October 2010.
> -# http://www.creston.museum.bc.ca/index.php?module=comments&uop=view_comment&cm+id=56
> -
> -# Here is a summary of the three clock change events in Creston's history:
> -# 1. 1884 or 1885: adoption of Mountain Standard Time (GMT-7)
> -# Exact date unknown
> -# 2. Oct 1916: switch to Pacific Standard Time (GMT-8)
> -# Exact date in October unknown; Sunday October 1 is a reasonable guess.
> -# 3. June 1918: switch to Pacific Daylight Time (GMT-7)
> -# Exact date in June unknown; Sunday June 2 is a reasonable guess.
> -# note 1:
> -# On Oct 27/1918 when daylight saving ended in the rest of Canada,
> -# Creston did not change its clocks.
> -# note 2:
> -# During WWII when the Federal Government legislated a mandatory clock change,
> -# Creston did not oblige.
> -# note 3:
> -# There is no guarantee that Creston will remain on Mountain Standard Time
> -# (UTC-7) forever.
> -# The subject was debated at least once this year by the town Council.
> -# http://www.bclocalnews.com/kootenay_rockies/crestonvalleyadvance/news/116760809.html
> -
> -# During a period WWII, summer time (Daylight saying) was mandatory in Canada.
> -# In Creston, that was handled by shifting the area to PST (-8:00) then applying
> -# summer time to cause the offset to be -7:00, the same as it had been before
> -# the change.  It can be argued that the timezone abbreviation during this
> -# period should be PDT rather than MST, but that doesn't seem important enough
> -# (to anyone) to further complicate the rules.
> -
> -# The transition dates (and times) are guesses.
>  
>  # From Matt Johnson (2015-09-21):
>  # Fort Nelson, BC, Canada will cancel DST this year.  So while previously they
> @@ -2144,10 +2021,7 @@ Zone America/Fort_Nelson	-8:10:47 -	LMT	1884
>  			-8:00	Vanc	P%sT	1987
>  			-8:00	Canada	P%sT	2015 Mar  8  2:00
>  			-7:00	-	MST
> -Zone America/Creston	-7:46:04 -	LMT	1884
> -			-7:00	-	MST	1916 Oct 1
> -			-8:00	-	PST	1918 Jun 2
> -			-7:00	-	MST
> +# For Creston see America/Phoenix.
>  
>  # Northwest Territories, Nunavut, Yukon
>  
> @@ -2929,50 +2803,11 @@ Zone America/Tijuana	-7:48:04 -	LMT	1922 Jan  1  0:11:56
>  
>  # Anguilla
>  # Antigua and Barbuda
> -# See America/Port_of_Spain.
> +# See America/Puerto_Rico.
>  
>  # The Bahamas
> -#
> -# For 1899 Milne gives -5:09:29.5; round that.
> -#
> -# From P Chan (2020-11-27, corrected on 2020-12-02):
> -# There were two periods of DST observed in 1942-1945: 1942-05-01
> -# midnight to 1944-12-31 midnight and 1945-02-01 to 1945-10-17 midnight.
> -# "midnight" should mean 24:00 from the context.
> -#
> -# War Time Order 1942 [1942-05-01] and War Time (No. 2) Order 1942  [1942-09-29]
> -# Appendix to the Statutes of 7 George VI. and the Year 1942. p 34, 43
> -# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA3-PA34
> -# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA3-PA43
> -#
> -# War Time Order 1943 [1943-03-31] and War Time Order 1944 [1943-12-29]
> -# Appendix to the Statutes of 8 George VI. and the Year 1943. p 9-10, 28-29
> -# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA4-PA9
> -# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA4-PA28
> -#
> -# War Time Order 1945 [1945-01-31] and the Order which revoke War Time Order
> -# 1945 [1945-10-16] Appendix to the Statutes of 9 George VI. and the Year
> -# 1945. p 160, 247-248
> -# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA6-PA160
> -# https://books.google.com/books?id=5rlNAQAAIAAJ&pg=RA6-PA247
> -#
> -# From Sue Williams (2006-12-07):
> -# The Bahamas announced about a month ago that they plan to change their DST
> -# rules to sync with the U.S. starting in 2007....
> -# http://www.jonesbahamas.com/?c=45&a=10412
> +# See America/Montreal.
>  
> -# Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
> -Rule	Bahamas	1942	only	-	May	 1	24:00	1:00	W
> -Rule	Bahamas	1944	only	-	Dec	31	24:00	0	S
> -Rule	Bahamas	1945	only	-	Feb	 1	0:00	1:00	W
> -Rule	Bahamas	1945	only	-	Aug	14	23:00u	1:00	P # Peace
> -Rule	Bahamas	1945	only	-	Oct	17	24:00	0	S
> -Rule	Bahamas	1964	1975	-	Oct	lastSun	2:00	0	S
> -Rule	Bahamas	1964	1975	-	Apr	lastSun	2:00	1:00	D
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	America/Nassau	-5:09:30 -	LMT	1912 Mar 2
> -			-5:00	Bahamas	E%sT	1976
> -			-5:00	US	E%sT
>  
>  # Barbados
>  
> @@ -3185,7 +3020,7 @@ Zone Atlantic/Bermuda	-4:19:18 -	LMT	1890	# Hamilton
>  			-4:00	US	A%sT
>  
>  # Caribbean Netherlands
> -# See America/Curacao.
> +# See America/Puerto_Rico.
>  
>  # Cayman Is
>  # See America/Panama.
> @@ -3415,7 +3250,7 @@ Zone	America/Havana	-5:29:28 -	LMT	1890
>  			-5:00	Cuba	C%sT
>  
>  # Dominica
> -# See America/Port_of_Spain.
> +# See America/Puerto_Rico.
>  
>  # Dominican Republic
>  
> @@ -3467,7 +3302,7 @@ Zone America/El_Salvador -5:56:48 -	LMT	1921 # San Salvador
>  # Guadeloupe
>  # St Barthélemy
>  # St Martin (French part)
> -# See America/Port_of_Spain.
> +# See America/Puerto_Rico.
>  
>  # Guatemala
>  #
> @@ -3654,7 +3489,7 @@ Zone America/Martinique	-4:04:20 -      LMT	1890        # Fort-de-France
>  			-4:00	-	AST
>  
>  # Montserrat
> -# See America/Port_of_Spain.
> +# See America/Puerto_Rico.
>  
>  # Nicaragua
>  #
> @@ -3737,7 +3572,7 @@ Zone America/Puerto_Rico -4:24:25 -	LMT	1899 Mar 28 12:00 # San Juan
>  
>  # St Kitts-Nevis
>  # St Lucia
> -# See America/Port_of_Spain.
> +# See America/Puerto_Rico.
>  
>  # St Pierre and Miquelon
>  # There are too many St Pierres elsewhere, so we'll use 'Miquelon'.
> @@ -3748,10 +3583,10 @@ Zone America/Miquelon	-3:44:40 -	LMT	1911 May 15 # St Pierre
>  			-3:00	Canada	-03/-02
>  
>  # St Vincent and the Grenadines
> -# See America/Port_of_Spain.
> +# See America/Puerto_Rico.
>  
>  # Sint Maarten
> -# See America/Curacao.
> +# See America/Puerto_Rico.
>  
>  # Turks and Caicos
>  #
> @@ -3823,7 +3658,7 @@ Zone America/Grand_Turk	-4:44:32 -	LMT	1890
>  
>  # British Virgin Is
>  # US Virgin Is
> -# See America/Port_of_Spain.
> +# See America/Puerto_Rico.
>  
>  
>  # Local Variables:
> diff --git a/southamerica b/southamerica
> index eb987c5..7bc3e70 100644
> --- a/southamerica
> +++ b/southamerica
> @@ -574,14 +574,11 @@ Zone America/Argentina/Ushuaia -4:33:12 - LMT	1894 Oct 31
>  			-3:00	-	-03
>  
>  # Aruba
> -# See America/Curacao.
> +# See America/Puerto_Rico.
>  
>  # Bolivia
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	America/La_Paz	-4:32:36 -	LMT	1890
> -			-4:32:36 -	CMT	1931 Oct 15 # Calamarca MT
> -			-4:32:36 1:00	BST	1932 Mar 21 # Bolivia ST
> -			-4:00	-	-04
> +# See Etc/GMT+4.
> +
>  
>  # Brazil
>  
> @@ -1369,33 +1366,12 @@ Zone	America/Bogota	-4:56:16 -	LMT	1884 Mar 13
>  # no information; probably like America/Bogota
>  
>  # Curaçao
> -
> -# Milne gives 4:35:46.9 for Curaçao mean time; round to nearest.
> +# See America/Puerto_Rico.
>  #
> -# From Paul Eggert (2006-03-22):
> -# Shanks & Pottenger say that The Bottom and Philipsburg have been at
> -# -4:00 since standard time was introduced on 1912-03-02; and that
> -# Kralendijk and Rincon used Kralendijk Mean Time (-4:33:08) from
> -# 1912-02-02 to 1965-01-01.  The former is dubious, since S&P also say
> -# Saba Island has been like Curaçao.
> -# This all predates our 1970 cutoff, though.
> -#
> -# By July 2007 Curaçao and St Maarten are planned to become
> -# associated states within the Netherlands, much like Aruba;
> -# Bonaire, Saba and St Eustatius would become directly part of the
> -# Netherlands as Kingdom Islands.  This won't affect their time zones
> -# though, as far as we know.
> -#
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone	America/Curacao	-4:35:47 -	LMT	1912 Feb 12 # Willemstad
> -			-4:30	-	-0430	1965
> -			-4:00	-	AST
> -
>  # From Arthur David Olson (2011-06-15):
>  # use links for places with new iso3166 codes.
>  # The name "Lower Prince's Quarter" is both longer than fourteen characters
> -# and contains an apostrophe; use "Lower_Princes" below.
> -
> +# and contains an apostrophe; use "Lower_Princes"....
>  # From Paul Eggert (2021-05-06):
>  # These backward-compatibility links now are in the 'backward' file.
>  
> @@ -1534,10 +1510,8 @@ Zone Atlantic/Stanley	-3:51:24 -	LMT	1890
>  			-3:00	-	-03
>  
>  # French Guiana
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone America/Cayenne	-3:29:20 -	LMT	1911 Jul
> -			-4:00	-	-04	1967 Oct
> -			-3:00	-	-03
> +# See Etc/GMT+3.
> +
>  
>  # Guyana
>  
> @@ -1698,9 +1672,7 @@ Zone	America/Lima	-5:08:12 -	LMT	1890
>  			-5:00	Peru	-05/-04
>  
>  # South Georgia
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone Atlantic/South_Georgia -2:26:08 -	LMT	1890 # Grytviken
> -			-2:00	-	-02
> +# See Etc/GMT+2.
>  
>  # South Sandwich Is
>  # uninhabited; scientific personnel have wintered
> @@ -1714,9 +1686,7 @@ Zone America/Paramaribo	-3:40:40 -	LMT	1911
>  			-3:00	-	-03
>  
>  # Trinidad and Tobago
> -# Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
> -Zone America/Port_of_Spain -4:06:04 -	LMT	1912 Mar 2
> -			-4:00	-	AST
> +# See America/Puerto_Rico.
>  
>  # Uruguay
>  # From Paul Eggert (1993-11-18):
> diff --git a/theory.html b/theory.html
> index 80942e6..47a7b2d 100644
> --- a/theory.html
> +++ b/theory.html
> @@ -192,8 +192,8 @@ in decreasing order of importance:
>      <code>TZ</code> strings</a>.
>      A file name component must not exceed 14 characters or start with
>      '<code>-</code>'.
> -    E.g., prefer <code>Asia/Brunei</code> to
> -    <code>Asia/Bandar_Seri_Begawan</code>.
> +    E.g., prefer <code>America/Noronha</code> to
> +    <code>America/Fernando_de_Noronha</code>.
>      Exceptions: see the discussion of legacy names below.
>    </li>
>    <li>
> @@ -475,10 +475,10 @@ in decreasing order of importance:
>  
>      <p>
>      <small>These abbreviations are:
> -      AMT Amsterdam, Asunción, Athens;
> -      BMT Baghdad, Bangkok, Batavia, Bermuda, Bern, Bogotá, Bridgetown,
> +      AMT Asunción, Athens;
> +      BMT Baghdad, Batavia, Bermuda, Bern, Bogotá, Bridgetown,
>          Brussels, Bucharest;
> -      CMT Calamarca, Caracas, Chisinau, Colón, Copenhagen, Córdoba;
> +      CMT Calamarca, Caracas, Chisinau, Colón, Córdoba;
>        DMT Dublin/Dunsink;
>        EMT Easter;
>        FFMT Fort-de-France;
> @@ -493,7 +493,6 @@ in decreasing order of importance:
>  	Moratuwa, Moscow;
>        PLMT Phù Liễn;
>        PMT Paramaribo, Paris, Perm, Pontianak, Prague;
> -      PMMT Port Moresby;
>        QMT Quito;
>        RMT Rangoon, Riga, Rome;
>        SDMT Santo Domingo;
> @@ -516,9 +515,7 @@ in decreasing order of importance:
>  	1880–1916,
>        MMT/MST/MDST for Moscow 1880–1919, and
>        RMT/LST for Riga Mean Time and Latvian Summer time 1880–1926.
> -    An extra-special case is SET for Swedish Time (<em>svensk
> -    normaltid</em>) 1879–1899, 3° west of the Stockholm
> -    Observatory.</small>
> +    </small>
>      </p>
>    </li>
>    <li>
> @@ -705,11 +702,9 @@ href="https://www.dissentmagazine.org/blog/booked-a-global-history-of-time-vanes
>    <li>
>      Sometimes historical timekeeping was specified more precisely
>      than what the <code><abbr>tz</abbr></code> code can handle.
> -    For example, from 1909 to 1937 <a
> -    href="https://www.staff.science.uu.nl/~gent0113/wettijd/wettijd.htm"
> -    hreflang="nl">Netherlands clocks</a> were legally Amsterdam Mean
> +    For example, from 1880 to 1916 clocks in Ireland observed Dublin Mean
>      Time (estimated to be <abbr>UT</abbr>
> -    +00:19:32.13), but the <code><abbr>tz</abbr></code>
> +    −00:25:21.1), but the <code><abbr>tz</abbr></code>
>      code cannot represent the fractional second.
>      In practice these old specifications were rarely if ever
>      implemented to subsecond precision.
> @@ -759,7 +754,7 @@ href="https://www.dissentmagazine.org/blog/booked-a-global-history-of-time-vanes
>      such as that required by POSIX.
>      If <abbr>DST</abbr> is not used a different time zone
>      can often do the trick; for example, in Kenya a <code>TZ</code> setting
> -    like <code><-03>3</code> or <code>America/Cayenne</code> starts
> +    like <code><-03>3</code> starts
>      the day six hours later than <code>Africa/Nairobi</code> does.
>    </li>
>    <li>
> @@ -1240,11 +1235,11 @@ based on guesswork and these guesses may be corrected or improved.
>  
>  <p>
>  Timezone boundaries are not part of the stable interface.
> -For example, even though the <samp>Asia/Bangkok</samp> timezone
> -currently includes Chang Mai, Hanoi, and Phnom Penh, this is not part
> +For example, even though the <samp>Asia/Singapore</samp> timezone
> +currently includes peninsular Malaysia as well as Singapore, this is not part
>  of the stable interface and the timezone can split at any time.
>  If a calendar application records a future event in some location other
> -than Bangkok by putting "<samp>Asia/Bangkok</samp>" in the event's record,
> +than Singapore by putting "<samp>Asia/Singapore</samp>" in the event's record,
>  the application should be robust in the presence of timezone splits
>  between now and the future time.
>  </p>
> diff --git a/zone.tab b/zone.tab
> index 291e4f3..4954ae3 100644
> --- a/zone.tab
> +++ b/zone.tab
> @@ -27,23 +27,23 @@
>  #country-
>  #code	coordinates	TZ			comments
>  AD	+4230+00131	Europe/Andorra
> -AE	+2518+05518	Asia/Dubai
> +AE	+2518+05518	Etc/GMT-4
>  AF	+3431+06912	Asia/Kabul
> -AG	+1703-06148	America/Port_of_Spain
> -AI	+1812-06304	America/Port_of_Spain
> +AG	+1703-06148	America/Puerto_Rico
> +AI	+1812-06304	America/Puerto_Rico
>  AL	+4120+01950	Europe/Tirane
>  AM	+4011+04430	Asia/Yerevan
>  AO	-0848+01314	Africa/Lagos
>  AQ	-7750+16636	Pacific/Auckland	New Zealand time - McMurdo, South Pole
>  AQ	-6617+11031	Antarctica/Casey	Casey
>  AQ	-6835+07758	Antarctica/Davis	Davis
> -AQ	-6640+14001	Antarctica/DumontDUrville	Dumont-d'Urville
> +AQ	-6640+14001	Etc/GMT-10	Dumont-d'Urville
>  AQ	-6736+06253	Antarctica/Mawson	Mawson
>  AQ	-6448-06406	Antarctica/Palmer	Palmer
>  AQ	-6734-06808	Antarctica/Rothera	Rothera
> -AQ	-690022+0393524	Antarctica/Syowa	Syowa
> +AQ	-690022+0393524	Etc/GMT-3	Syowa
>  AQ	-720041+0023206	Antarctica/Troll	Troll
> -AQ	-7824+10654	Antarctica/Vostok	Vostok
> +AQ	-7824+10654	Etc/GMT-6	Vostok
>  AR	-3436-05827	America/Argentina/Buenos_Aires	Buenos Aires (BA, CF)
>  AR	-3124-06411	America/Argentina/Cordoba	Argentina (most areas: CB, CC, CN, ER, FM, MN, SE, SF)
>  AR	-2447-06525	America/Argentina/Salta	Salta (SA, LP, NQ, RN)
> @@ -70,23 +70,23 @@ AU	-3455+13835	Australia/Adelaide	South Australia
>  AU	-1228+13050	Australia/Darwin	Northern Territory
>  AU	-3157+11551	Australia/Perth	Western Australia (most areas)
>  AU	-3143+12852	Australia/Eucla	Western Australia (Eucla)
> -AW	+1230-06958	America/Curacao
> +AW	+1230-06958	America/Puerto_Rico
>  AX	+6006+01957	Europe/Helsinki
>  AZ	+4023+04951	Asia/Baku
>  BA	+4352+01825	Europe/Belgrade
>  BB	+1306-05937	America/Barbados
>  BD	+2343+09025	Asia/Dhaka
>  BE	+5050+00420	Europe/Brussels
> -BF	+1222-00131	Africa/Abidjan
> +BF	+1222-00131	Etc/GMT
>  BG	+4241+02319	Europe/Sofia
>  BH	+2623+05035	Asia/Qatar
>  BI	-0323+02922	Africa/Maputo
>  BJ	+0629+00237	Africa/Lagos
> -BL	+1753-06251	America/Port_of_Spain
> +BL	+1753-06251	America/Puerto_Rico
>  BM	+3217-06446	Atlantic/Bermuda
> -BN	+0456+11455	Asia/Brunei
> -BO	-1630-06809	America/La_Paz
> -BQ	+120903-0681636	America/Curacao
> +BN	+0456+11455	Etc/GMT-8
> +BO	-1630-06809	Etc/GMT+4
> +BQ	+120903-0681636	America/Puerto_Rico
>  BR	-0351-03225	America/Noronha	Atlantic islands
>  BR	-0127-04829	America/Belem	Para (east); Amapa
>  BR	-0343-03830	America/Fortaleza	Brazil (northeast: MA, PI, CE, RN, PB)
> @@ -103,7 +103,7 @@ BR	+0249-06040	America/Boa_Vista	Roraima
>  BR	-0308-06001	America/Manaus	Amazonas (east)
>  BR	-0640-06952	America/Eirunepe	Amazonas (west)
>  BR	-0958-06748	America/Rio_Branco	Acre
> -BS	+2505-07721	America/Nassau
> +BS	+2505-07721	America/Toronto
>  BT	+2728+08939	Asia/Thimphu
>  BW	-2439+02555	Africa/Maputo
>  BY	+5354+02734	Europe/Minsk
> @@ -113,13 +113,13 @@ CA	+4439-06336	America/Halifax	Atlantic - NS (most areas); PE
>  CA	+4612-05957	America/Glace_Bay	Atlantic - NS (Cape Breton)
>  CA	+4606-06447	America/Moncton	Atlantic - New Brunswick
>  CA	+5320-06025	America/Goose_Bay	Atlantic - Labrador (most areas)
> -CA	+5125-05707	America/Blanc-Sablon	AST - QC (Lower North Shore)
> +CA	+5125-05707	America/Puerto_Rico	AST - QC (Lower North Shore)
>  CA	+4339-07923	America/Toronto	Eastern - ON, QC (most areas)
>  CA	+4901-08816	America/Nipigon	Eastern - ON, QC (no DST 1967-73)
>  CA	+4823-08915	America/Thunder_Bay	Eastern - ON (Thunder Bay)
>  CA	+6344-06828	America/Iqaluit	Eastern - NU (most east areas)
>  CA	+6608-06544	America/Pangnirtung	Eastern - NU (Pangnirtung)
> -CA	+484531-0913718	America/Atikokan	EST - ON (Atikokan); NU (Coral H)
> +CA	+484531-0913718	America/Panama	EST - ON (Atikokan); NU (Coral H)
>  CA	+4953-09709	America/Winnipeg	Central - ON (west); Manitoba
>  CA	+4843-09434	America/Rainy_River	Central - ON (Rainy R, Ft Frances)
>  CA	+744144-0944945	America/Resolute	Central - NU (Resolute)
> @@ -130,40 +130,40 @@ CA	+5333-11328	America/Edmonton	Mountain - AB; BC (E); SK (W)
>  CA	+690650-1050310	America/Cambridge_Bay	Mountain - NU (west)
>  CA	+6227-11421	America/Yellowknife	Mountain - NT (central)
>  CA	+682059-1334300	America/Inuvik	Mountain - NT (west)
> -CA	+4906-11631	America/Creston	MST - BC (Creston)
> +CA	+4906-11631	America/Phoenix	MST - BC (Creston)
>  CA	+5946-12014	America/Dawson_Creek	MST - BC (Dawson Cr, Ft St John)
>  CA	+5848-12242	America/Fort_Nelson	MST - BC (Ft Nelson)
>  CA	+6043-13503	America/Whitehorse	MST - Yukon (east)
>  CA	+6404-13925	America/Dawson	MST - Yukon (west)
>  CA	+4916-12307	America/Vancouver	Pacific - BC (most areas)
> -CC	-1210+09655	Indian/Cocos
> +CC	-1210+09655	Asia/Yangon
>  CD	-0418+01518	Africa/Lagos	Dem. Rep. of Congo (west)
>  CD	-1140+02728	Africa/Maputo	Dem. Rep. of Congo (east)
>  CF	+0422+01835	Africa/Lagos
>  CG	-0416+01517	Africa/Lagos
>  CH	+4723+00832	Europe/Zurich
> -CI	+0519-00402	Africa/Abidjan
> +CI	+0519-00402	Etc/GMT
>  CK	-2114-15946	Pacific/Rarotonga
>  CL	-3327-07040	America/Santiago	Chile (most areas)
>  CL	-5309-07055	America/Punta_Arenas	Region of Magallanes
>  CL	-2709-10926	Pacific/Easter	Easter Island
>  CM	+0403+00942	Africa/Lagos
>  CN	+3114+12128	Asia/Shanghai	Beijing Time
> -CN	+4348+08735	Asia/Urumqi	Xinjiang Time
> +CN	+4348+08735	Etc/GMT-6	Xinjiang Time
>  CO	+0436-07405	America/Bogota
>  CR	+0956-08405	America/Costa_Rica
>  CU	+2308-08222	America/Havana
>  CV	+1455-02331	Atlantic/Cape_Verde
> -CW	+1211-06900	America/Curacao
> -CX	-1025+10543	Indian/Christmas
> +CW	+1211-06900	America/Puerto_Rico
> +CX	-1025+10543	Etc/GMT-7
>  CY	+3510+03322	Asia/Nicosia	Cyprus (most areas)
>  CY	+3507+03357	Asia/Famagusta	Northern Cyprus
>  CZ	+5005+01426	Europe/Prague
>  DE	+5230+01322	Europe/Berlin	Germany (most areas)
>  DE	+4742+00841	Europe/Zurich	Swiss time
>  DJ	+1136+04309	Africa/Nairobi
> -DK	+5540+01235	Europe/Copenhagen
> -DM	+1518-06124	America/Port_of_Spain
> +DK	+5540+01235	Europe/Berlin
> +DM	+1518-06124	America/Puerto_Rico
>  DO	+1828-06954	America/Santo_Domingo
>  DZ	+3647+00303	Africa/Algiers
>  EC	-0210-07950	America/Guayaquil	Ecuador (mainland)
> @@ -179,29 +179,29 @@ ET	+0902+03842	Africa/Nairobi
>  FI	+6010+02458	Europe/Helsinki
>  FJ	-1808+17825	Pacific/Fiji
>  FK	-5142-05751	Atlantic/Stanley
> -FM	+0725+15147	Pacific/Chuuk	Chuuk/Truk, Yap
> -FM	+0658+15813	Pacific/Pohnpei	Pohnpei/Ponape
> +FM	+0725+15147	Etc/GMT-10	Chuuk/Truk, Yap
> +FM	+0658+15813	Etc/GMT-11	Pohnpei/Ponape
>  FM	+0519+16259	Pacific/Kosrae	Kosrae
>  FO	+6201-00646	Atlantic/Faroe
>  FR	+4852+00220	Europe/Paris
>  GA	+0023+00927	Africa/Lagos
>  GB	+513030-0000731	Europe/London
> -GD	+1203-06145	America/Port_of_Spain
> +GD	+1203-06145	America/Puerto_Rico
>  GE	+4143+04449	Asia/Tbilisi
> -GF	+0456-05220	America/Cayenne
> +GF	+0456-05220	Etc/GMT+3
>  GG	+492717-0023210	Europe/London
> -GH	+0533-00013	Africa/Accra
> +GH	+0533-00013	Etc/GMT
>  GI	+3608-00521	Europe/Gibraltar
>  GL	+6411-05144	America/Nuuk	Greenland (most areas)
>  GL	+7646-01840	America/Danmarkshavn	National Park (east coast)
>  GL	+7029-02158	America/Scoresbysund	Scoresbysund/Ittoqqortoormiit
>  GL	+7634-06847	America/Thule	Thule/Pituffik
> -GM	+1328-01639	Africa/Abidjan
> -GN	+0931-01343	Africa/Abidjan
> -GP	+1614-06132	America/Port_of_Spain
> +GM	+1328-01639	Etc/GMT
> +GN	+0931-01343	Etc/GMT
> +GP	+1614-06132	America/Puerto_Rico
>  GQ	+0345+00847	Africa/Lagos
>  GR	+3758+02343	Europe/Athens
> -GS	-5416-03632	Atlantic/South_Georgia
> +GS	-5416-03632	Etc/GMT+2
>  GT	+1438-09031	America/Guatemala
>  GU	+1328+14445	Pacific/Guam
>  GW	+1151-01535	Africa/Bissau
> @@ -222,7 +222,7 @@ IN	+2232+08822	Asia/Kolkata
>  IO	-0720+07225	Indian/Chagos
>  IQ	+3321+04425	Asia/Baghdad
>  IR	+3540+05126	Asia/Tehran
> -IS	+6409-02151	Atlantic/Reykjavik
> +IS	+6409-02151	Etc/GMT
>  IT	+4154+01229	Europe/Rome
>  JE	+491101-0020624	Europe/London
>  JM	+175805-0764736	America/Jamaica
> @@ -230,15 +230,15 @@ JO	+3157+03556	Asia/Amman
>  JP	+353916+1394441	Asia/Tokyo
>  KE	-0117+03649	Africa/Nairobi
>  KG	+4254+07436	Asia/Bishkek
> -KH	+1133+10455	Asia/Bangkok
> -KI	+0125+17300	Pacific/Tarawa	Gilbert Islands
> +KH	+1133+10455	Etc/GMT-7
> +KI	+0125+17300	Etc/GMT-12	Gilbert Islands
>  KI	-0308-17105	Pacific/Enderbury	Phoenix Islands
>  KI	+0152-15720	Pacific/Kiritimati	Line Islands
>  KM	-1141+04316	Africa/Nairobi
> -KN	+1718-06243	America/Port_of_Spain
> +KN	+1718-06243	America/Puerto_Rico
>  KP	+3901+12545	Asia/Pyongyang
>  KR	+3733+12658	Asia/Seoul
> -KW	+2920+04759	Asia/Riyadh
> +KW	+2920+04759	Etc/GMT-3
>  KY	+1918-08123	America/Panama
>  KZ	+4315+07657	Asia/Almaty	Kazakhstan (most areas)
>  KZ	+4448+06528	Asia/Qyzylorda	Qyzylorda/Kyzylorda/Kzyl-Orda
> @@ -247,27 +247,27 @@ KZ	+5017+05710	Asia/Aqtobe	Aqtobe/Aktobe
>  KZ	+4431+05016	Asia/Aqtau	Mangghystau/Mankistau
>  KZ	+4707+05156	Asia/Atyrau	Atyrau/Atirau/Gur'yev
>  KZ	+5113+05121	Asia/Oral	West Kazakhstan
> -LA	+1758+10236	Asia/Bangkok
> +LA	+1758+10236	Etc/GMT-7
>  LB	+3353+03530	Asia/Beirut
> -LC	+1401-06100	America/Port_of_Spain
> +LC	+1401-06100	America/Puerto_Rico
>  LI	+4709+00931	Europe/Zurich
>  LK	+0656+07951	Asia/Colombo
>  LR	+0618-01047	Africa/Monrovia
>  LS	-2928+02730	Africa/Johannesburg
>  LT	+5441+02519	Europe/Vilnius
> -LU	+4936+00609	Europe/Luxembourg
> +LU	+4936+00609	Europe/Brussels
>  LV	+5657+02406	Europe/Riga
>  LY	+3254+01311	Africa/Tripoli
>  MA	+3339-00735	Africa/Casablanca
> -MC	+4342+00723	Europe/Monaco
> +MC	+4342+00723	Europe/Paris
>  MD	+4700+02850	Europe/Chisinau
>  ME	+4226+01916	Europe/Belgrade
> -MF	+1804-06305	America/Port_of_Spain
> +MF	+1804-06305	America/Puerto_Rico
>  MG	-1855+04731	Africa/Nairobi
> -MH	+0709+17112	Pacific/Majuro	Marshall Islands (most areas)
> +MH	+0709+17112	Etc/GMT-12	Marshall Islands (most areas)
>  MH	+0905+16720	Pacific/Kwajalein	Kwajalein
>  MK	+4159+02126	Europe/Belgrade
> -ML	+1239-00800	Africa/Abidjan
> +ML	+1239-00800	Etc/GMT
>  MM	+1647+09610	Asia/Yangon
>  MN	+4755+10653	Asia/Ulaanbaatar	Mongolia (most areas)
>  MN	+4801+09139	Asia/Hovd	Bayan-Olgiy, Govi-Altai, Hovd, Uvs, Zavkhan
> @@ -275,11 +275,11 @@ MN	+4804+11430	Asia/Choibalsan	Dornod, Sukhbaatar
>  MO	+221150+1133230	Asia/Macau
>  MP	+1512+14545	Pacific/Guam
>  MQ	+1436-06105	America/Martinique
> -MR	+1806-01557	Africa/Abidjan
> -MS	+1643-06213	America/Port_of_Spain
> +MR	+1806-01557	Etc/GMT
> +MS	+1643-06213	America/Puerto_Rico
>  MT	+3554+01431	Europe/Malta
>  MU	-2010+05730	Indian/Mauritius
> -MV	+0410+07330	Indian/Maldives
> +MV	+0410+07330	Etc/GMT-5
>  MW	-1547+03500	Africa/Maputo
>  MX	+1924-09909	America/Mexico_City	Central Time
>  MX	+2105-08646	America/Cancun	Eastern Standard Time - Quintana Roo
> @@ -292,8 +292,8 @@ MX	+2934-10425	America/Ojinaga	Mountain Time US - Chihuahua (US border)
>  MX	+2904-11058	America/Hermosillo	Mountain Standard Time - Sonora
>  MX	+3232-11701	America/Tijuana	Pacific Time US - Baja California
>  MX	+2048-10515	America/Bahia_Banderas	Central Time - Bahia de Banderas
> -MY	+0310+10142	Asia/Kuala_Lumpur	Malaysia (peninsula)
> -MY	+0133+11020	Asia/Kuching	Sabah, Sarawak
> +MY	+0310+10142	Asia/Singapore	Malaysia (peninsula)
> +MY	+0133+11020	Etc/GMT-8	Sabah, Sarawak
>  MZ	-2558+03235	Africa/Maputo
>  NA	-2234+01706	Africa/Windhoek
>  NC	-2216+16627	Pacific/Noumea
> @@ -301,20 +301,20 @@ NE	+1331+00207	Africa/Lagos
>  NF	-2903+16758	Pacific/Norfolk
>  NG	+0627+00324	Africa/Lagos
>  NI	+1209-08617	America/Managua
> -NL	+5222+00454	Europe/Amsterdam
> -NO	+5955+01045	Europe/Oslo
> +NL	+5222+00454	Europe/Brussels
> +NO	+5955+01045	Europe/Berlin
>  NP	+2743+08519	Asia/Kathmandu
>  NR	-0031+16655	Pacific/Nauru
>  NU	-1901-16955	Pacific/Niue
>  NZ	-3652+17446	Pacific/Auckland	New Zealand (most areas)
>  NZ	-4357-17633	Pacific/Chatham	Chatham Islands
> -OM	+2336+05835	Asia/Dubai
> +OM	+2336+05835	Etc/GMT-4
>  PA	+0858-07932	America/Panama
>  PE	-1203-07703	America/Lima
> -PF	-1732-14934	Pacific/Tahiti	Society Islands
> +PF	-1732-14934	Etc/GMT+10	Society Islands
>  PF	-0900-13930	Pacific/Marquesas	Marquesas Islands
> -PF	-2308-13457	Pacific/Gambier	Gambier Islands
> -PG	-0930+14710	Pacific/Port_Moresby	Papua New Guinea (most areas)
> +PF	-2308-13457	Etc/GMT+9	Gambier Islands
> +PG	-0930+14710	Etc/GMT-10	Papua New Guinea (most areas)
>  PG	-0613+15534	Pacific/Bougainville	Bougainville
>  PH	+1435+12100	Asia/Manila
>  PK	+2452+06703	Asia/Karachi
> @@ -327,10 +327,10 @@ PS	+313200+0350542	Asia/Hebron	West Bank
>  PT	+3843-00908	Europe/Lisbon	Portugal (mainland)
>  PT	+3238-01654	Atlantic/Madeira	Madeira Islands
>  PT	+3744-02540	Atlantic/Azores	Azores
> -PW	+0720+13429	Pacific/Palau
> +PW	+0720+13429	Etc/GMT-9
>  PY	-2516-05740	America/Asuncion
>  QA	+2517+05132	Asia/Qatar
> -RE	-2052+05528	Indian/Reunion
> +RE	-2052+05528	Etc/GMT-4
>  RO	+4426+02606	Europe/Bucharest
>  RS	+4450+02030	Europe/Belgrade
>  RU	+5443+02030	Europe/Kaliningrad	MSK-01 - Kaliningrad
> @@ -364,32 +364,32 @@ RU	+6728+15343	Asia/Srednekolymsk	MSK+08 - Sakha (E); North Kuril Is
>  RU	+5301+15839	Asia/Kamchatka	MSK+09 - Kamchatka
>  RU	+6445+17729	Asia/Anadyr	MSK+09 - Bering Sea
>  RW	-0157+03004	Africa/Maputo
> -SA	+2438+04643	Asia/Riyadh
> -SB	-0932+16012	Pacific/Guadalcanal
> -SC	-0440+05528	Indian/Mahe
> +SA	+2438+04643	Etc/GMT-3
> +SB	-0932+16012	Etc/GMT-11
> +SC	-0440+05528	Etc/GMT-4
>  SD	+1536+03232	Africa/Khartoum
> -SE	+5920+01803	Europe/Stockholm
> +SE	+5920+01803	Europe/Berlin
>  SG	+0117+10351	Asia/Singapore
> -SH	-1555-00542	Africa/Abidjan
> +SH	-1555-00542	Etc/GMT
>  SI	+4603+01431	Europe/Belgrade
> -SJ	+7800+01600	Europe/Oslo
> +SJ	+7800+01600	Europe/Berlin
>  SK	+4809+01707	Europe/Prague
> -SL	+0830-01315	Africa/Abidjan
> +SL	+0830-01315	Etc/GMT
>  SM	+4355+01228	Europe/Rome
> -SN	+1440-01726	Africa/Abidjan
> +SN	+1440-01726	Etc/GMT
>  SO	+0204+04522	Africa/Nairobi
>  SR	+0550-05510	America/Paramaribo
>  SS	+0451+03137	Africa/Juba
>  ST	+0020+00644	Africa/Sao_Tome
>  SV	+1342-08912	America/El_Salvador
> -SX	+180305-0630250	America/Curacao
> +SX	+180305-0630250	America/Puerto_Rico
>  SY	+3330+03618	Asia/Damascus
>  SZ	-2618+03106	Africa/Johannesburg
>  TC	+2128-07108	America/Grand_Turk
>  TD	+1207+01503	Africa/Ndjamena
> -TF	-492110+0701303	Indian/Kerguelen
> -TG	+0608+00113	Africa/Abidjan
> -TH	+1345+10031	Asia/Bangkok
> +TF	-492110+0701303	Etc/GMT-5
> +TG	+0608+00113	Etc/GMT
> +TH	+1345+10031	Etc/GMT-7
>  TJ	+3835+06848	Asia/Dushanbe
>  TK	-0922-17114	Pacific/Fakaofo
>  TL	-0833+12535	Asia/Dili
> @@ -397,8 +397,8 @@ TM	+3757+05823	Asia/Ashgabat
>  TN	+3648+01011	Africa/Tunis
>  TO	-210800-1751200	Pacific/Tongatapu
>  TR	+4101+02858	Europe/Istanbul
> -TT	+1039-06131	America/Port_of_Spain
> -TV	-0831+17913	Pacific/Funafuti
> +TT	+1039-06131	America/Puerto_Rico
> +TV	-0831+17913	Etc/GMT-12
>  TW	+2503+12130	Asia/Taipei
>  TZ	-0648+03917	Africa/Nairobi
>  UA	+5026+03031	Europe/Kiev	Ukraine (most areas)
> @@ -406,7 +406,7 @@ UA	+4837+02218	Europe/Uzhgorod	Transcarpathia
>  UA	+4750+03510	Europe/Zaporozhye	Zaporozhye and east Lugansk
>  UG	+0019+03225	Africa/Nairobi
>  UM	+2813-17722	Pacific/Pago_Pago	Midway Islands
> -UM	+1917+16637	Pacific/Wake	Wake Island
> +UM	+1917+16637	Etc/GMT-12	Wake Island
>  US	+404251-0740023	America/New_York	Eastern (most areas)
>  US	+421953-0830245	America/Detroit	Eastern - MI (most areas)
>  US	+381515-0854534	America/Kentucky/Louisville	Eastern - KY (Louisville area)
> @@ -440,16 +440,16 @@ UY	-345433-0561245	America/Montevideo
>  UZ	+3940+06648	Asia/Samarkand	Uzbekistan (west)
>  UZ	+4120+06918	Asia/Tashkent	Uzbekistan (east)
>  VA	+415408+0122711	Europe/Rome
> -VC	+1309-06114	America/Port_of_Spain
> +VC	+1309-06114	America/Puerto_Rico
>  VE	+1030-06656	America/Caracas
> -VG	+1827-06437	America/Port_of_Spain
> -VI	+1821-06456	America/Port_of_Spain
> -VN	+2102+10551	Asia/Bangkok	Vietnam (north)
> +VG	+1827-06437	America/Puerto_Rico
> +VI	+1821-06456	America/Puerto_Rico
> +VN	+2102+10551	Etc/GMT-7	Vietnam (north)
>  VN	+1045+10640	Asia/Ho_Chi_Minh	Vietnam (south)
>  VU	-1740+16825	Pacific/Efate
> -WF	-1318-17610	Pacific/Wallis
> +WF	-1318-17610	Etc/GMT-12
>  WS	-1350-17144	Pacific/Apia
> -YE	+1245+04512	Asia/Riyadh
> +YE	+1245+04512	Etc/GMT-3
>  YT	-1247+04514	Africa/Nairobi
>  ZA	-2615+02800	Africa/Johannesburg
>  ZM	-1525+02817	Africa/Maputo
> diff --git a/zone1970.tab b/zone1970.tab
> index ddb2321..8cadd48 100644
> --- a/zone1970.tab
> +++ b/zone1970.tab
> @@ -34,19 +34,18 @@
>  #country-
>  #codes	coordinates	TZ	comments
>  AD	+4230+00131	Europe/Andorra
> -AE,OM	+2518+05518	Asia/Dubai
> +AE,OM,RE,SC,TF	+2518+05518	Etc/GMT-4	UAE, Oman, Réunion, Seychelles, Crozet, Scattered Is
>  AF	+3431+06912	Asia/Kabul
>  AL	+4120+01950	Europe/Tirane
>  AM	+4011+04430	Asia/Yerevan
>  AQ	-6617+11031	Antarctica/Casey	Casey
>  AQ	-6835+07758	Antarctica/Davis	Davis
> -AQ	-6640+14001	Antarctica/DumontDUrville	Dumont-d'Urville
>  AQ	-6736+06253	Antarctica/Mawson	Mawson
>  AQ	-6448-06406	Antarctica/Palmer	Palmer
>  AQ	-6734-06808	Antarctica/Rothera	Rothera
> -AQ	-690022+0393524	Antarctica/Syowa	Syowa
>  AQ	-720041+0023206	Antarctica/Troll	Troll
> -AQ	-7824+10654	Antarctica/Vostok	Vostok
> +AQ,KW,SA,YE	+2438+04643	Etc/GMT-3	Arabia, Syowa
> +AQ,FM,PG	-0930+14710	Etc/GMT-10	Papua New Guinea (most areas), Chuuk, Yap, Dumont d'Urville
>  AR	-3436-05827	America/Argentina/Buenos_Aires	Buenos Aires (BA, CF)
>  AR	-3124-06411	America/Argentina/Cordoba	Argentina (most areas: CB, CC, CN, ER, FM, MN, SE, SF)
>  AR	-2447-06525	America/Argentina/Salta	Salta (SA, LP, NQ, RN)
> @@ -76,11 +75,12 @@ AU	-3143+12852	Australia/Eucla	Western Australia (Eucla)
>  AZ	+4023+04951	Asia/Baku
>  BB	+1306-05937	America/Barbados
>  BD	+2343+09025	Asia/Dhaka
> -BE	+5050+00420	Europe/Brussels
> +BE,LU,NL	+5050+00420	Europe/Brussels
> +BF,CI,GH,GM,GN,IS,ML,MR,SH,SL,SN,TG	+0519-00402	Etc/GMT
>  BG	+4241+02319	Europe/Sofia
>  BM	+3217-06446	Atlantic/Bermuda
> -BN	+0456+11455	Asia/Brunei
> -BO	-1630-06809	America/La_Paz
> +BN,MY	+0133+11020	Etc/GMT-8	Sabah, Sarawak, Brunei
> +BO	-1630-06809	Etc/GMT+4
>  BR	-0351-03225	America/Noronha	Atlantic islands
>  BR	-0127-04829	America/Belem	Pará (east); Amapá
>  BR	-0343-03830	America/Fortaleza	Brazil (northeast: MA, PI, CE, RN, PB)
> @@ -97,7 +97,6 @@ BR	+0249-06040	America/Boa_Vista	Roraima
>  BR	-0308-06001	America/Manaus	Amazonas (east)
>  BR	-0640-06952	America/Eirunepe	Amazonas (west)
>  BR	-0958-06748	America/Rio_Branco	Acre
> -BS	+2505-07721	America/Nassau
>  BT	+2728+08939	Asia/Thimphu
>  BY	+5354+02734	Europe/Minsk
>  BZ	+1730-08812	America/Belize
> @@ -106,13 +105,11 @@ CA	+4439-06336	America/Halifax	Atlantic - NS (most areas); PE
>  CA	+4612-05957	America/Glace_Bay	Atlantic - NS (Cape Breton)
>  CA	+4606-06447	America/Moncton	Atlantic - New Brunswick
>  CA	+5320-06025	America/Goose_Bay	Atlantic - Labrador (most areas)
> -CA	+5125-05707	America/Blanc-Sablon	AST - QC (Lower North Shore)
> -CA	+4339-07923	America/Toronto	Eastern - ON, QC (most areas)
> +CA,BS	+4339-07923	America/Toronto	Eastern - ON, QC (most areas), Bahamas
>  CA	+4901-08816	America/Nipigon	Eastern - ON, QC (no DST 1967-73)
>  CA	+4823-08915	America/Thunder_Bay	Eastern - ON (Thunder Bay)
>  CA	+6344-06828	America/Iqaluit	Eastern - NU (most east areas)
>  CA	+6608-06544	America/Pangnirtung	Eastern - NU (Pangnirtung)
> -CA	+484531-0913718	America/Atikokan	EST - ON (Atikokan); NU (Coral H)
>  CA	+4953-09709	America/Winnipeg	Central - ON (west); Manitoba
>  CA	+4843-09434	America/Rainy_River	Central - ON (Rainy R, Ft Frances)
>  CA	+744144-0944945	America/Resolute	Central - NU (Resolute)
> @@ -123,32 +120,27 @@ CA	+5333-11328	America/Edmonton	Mountain - AB; BC (E); SK (W)
>  CA	+690650-1050310	America/Cambridge_Bay	Mountain - NU (west)
>  CA	+6227-11421	America/Yellowknife	Mountain - NT (central)
>  CA	+682059-1334300	America/Inuvik	Mountain - NT (west)
> -CA	+4906-11631	America/Creston	MST - BC (Creston)
>  CA	+5946-12014	America/Dawson_Creek	MST - BC (Dawson Cr, Ft St John)
>  CA	+5848-12242	America/Fort_Nelson	MST - BC (Ft Nelson)
>  CA	+6043-13503	America/Whitehorse	MST - Yukon (east)
>  CA	+6404-13925	America/Dawson	MST - Yukon (west)
>  CA	+4916-12307	America/Vancouver	Pacific - BC (most areas)
> -CC	-1210+09655	Indian/Cocos
>  CH,DE,LI	+4723+00832	Europe/Zurich	Swiss time
> -CI,BF,GM,GN,ML,MR,SH,SL,SN,TG	+0519-00402	Africa/Abidjan
>  CK	-2114-15946	Pacific/Rarotonga
>  CL	-3327-07040	America/Santiago	Chile (most areas)
>  CL	-5309-07055	America/Punta_Arenas	Region of Magallanes
>  CL	-2709-10926	Pacific/Easter	Easter Island
>  CN	+3114+12128	Asia/Shanghai	Beijing Time
> -CN	+4348+08735	Asia/Urumqi	Xinjiang Time
> +CN,AQ	+4348+08735	Etc/GMT-6	Xinjiang Time, Vostok
>  CO	+0436-07405	America/Bogota
>  CR	+0956-08405	America/Costa_Rica
>  CU	+2308-08222	America/Havana
>  CV	+1455-02331	Atlantic/Cape_Verde
> -CW,AW,BQ,SX	+1211-06900	America/Curacao
> -CX	-1025+10543	Indian/Christmas
> +CX,KH,LA,TH,VN	+1345+10031	Etc/GMT-7	Indochina (most areas)
>  CY	+3510+03322	Asia/Nicosia	Cyprus (most areas)
>  CY	+3507+03357	Asia/Famagusta	Northern Cyprus
>  CZ,SK	+5005+01426	Europe/Prague
> -DE	+5230+01322	Europe/Berlin	Germany (most areas)
> -DK	+5540+01235	Europe/Copenhagen
> +DE,DK,NO,SE,SJ	+5230+01322	Europe/Berlin	Germany (most areas), Scandinavia
>  DO	+1828-06954	America/Santo_Domingo
>  DZ	+3647+00303	Africa/Algiers
>  EC	-0210-07950	America/Guayaquil	Ecuador (mainland)
> @@ -162,22 +154,19 @@ ES	+2806-01524	Atlantic/Canary	Canary Islands
>  FI,AX	+6010+02458	Europe/Helsinki
>  FJ	-1808+17825	Pacific/Fiji
>  FK	-5142-05751	Atlantic/Stanley
> -FM	+0725+15147	Pacific/Chuuk	Chuuk/Truk, Yap
> -FM	+0658+15813	Pacific/Pohnpei	Pohnpei/Ponape
>  FM	+0519+16259	Pacific/Kosrae	Kosrae
>  FO	+6201-00646	Atlantic/Faroe
> -FR	+4852+00220	Europe/Paris
> +FR,MC	+4852+00220	Europe/Paris
>  GB,GG,IM,JE	+513030-0000731	Europe/London
>  GE	+4143+04449	Asia/Tbilisi
> -GF	+0456-05220	America/Cayenne
> -GH	+0533-00013	Africa/Accra
> +GF	+0456-05220	Etc/GMT+3
>  GI	+3608-00521	Europe/Gibraltar
>  GL	+6411-05144	America/Nuuk	Greenland (most areas)
>  GL	+7646-01840	America/Danmarkshavn	National Park (east coast)
>  GL	+7029-02158	America/Scoresbysund	Scoresbysund/Ittoqqortoormiit
>  GL	+7634-06847	America/Thule	Thule/Pituffik
>  GR	+3758+02343	Europe/Athens
> -GS	-5416-03632	Atlantic/South_Georgia
> +GS	-5416-03632	Etc/GMT+2
>  GT	+1438-09031	America/Guatemala
>  GU,MP	+1328+14445	Pacific/Guam
>  GW	+1151-01535	Africa/Bissau
> @@ -196,16 +185,15 @@ IN	+2232+08822	Asia/Kolkata
>  IO	-0720+07225	Indian/Chagos
>  IQ	+3321+04425	Asia/Baghdad
>  IR	+3540+05126	Asia/Tehran
> -IS	+6409-02151	Atlantic/Reykjavik
>  IT,SM,VA	+4154+01229	Europe/Rome
>  JM	+175805-0764736	America/Jamaica
>  JO	+3157+03556	Asia/Amman
>  JP	+353916+1394441	Asia/Tokyo
>  KE,DJ,ER,ET,KM,MG,SO,TZ,UG,YT	-0117+03649	Africa/Nairobi
>  KG	+4254+07436	Asia/Bishkek
> -KI	+0125+17300	Pacific/Tarawa	Gilbert Islands
>  KI	-0308-17105	Pacific/Enderbury	Phoenix Islands
>  KI	+0152-15720	Pacific/Kiritimati	Line Islands
> +KI,MH,TV,UM,WF	+0125+17300	Etc/GMT-12	Gilberts, Marshalls, Tuvalu, Wallis & Futuna, Wake
>  KP	+3901+12545	Asia/Pyongyang
>  KR	+3733+12658	Asia/Seoul
>  KZ	+4315+07657	Asia/Almaty	Kazakhstan (most areas)
> @@ -219,15 +207,12 @@ LB	+3353+03530	Asia/Beirut
>  LK	+0656+07951	Asia/Colombo
>  LR	+0618-01047	Africa/Monrovia
>  LT	+5441+02519	Europe/Vilnius
> -LU	+4936+00609	Europe/Luxembourg
>  LV	+5657+02406	Europe/Riga
>  LY	+3254+01311	Africa/Tripoli
>  MA	+3339-00735	Africa/Casablanca
> -MC	+4342+00723	Europe/Monaco
>  MD	+4700+02850	Europe/Chisinau
> -MH	+0709+17112	Pacific/Majuro	Marshall Islands (most areas)
>  MH	+0905+16720	Pacific/Kwajalein	Kwajalein
> -MM	+1647+09610	Asia/Yangon
> +MM,CC	+1647+09610	Asia/Yangon
>  MN	+4755+10653	Asia/Ulaanbaatar	Mongolia (most areas)
>  MN	+4801+09139	Asia/Hovd	Bayan-Ölgii, Govi-Altai, Hovd, Uvs, Zavkhan
>  MN	+4804+11430	Asia/Choibalsan	Dornod, Sükhbaatar
> @@ -235,7 +220,7 @@ MO	+221150+1133230	Asia/Macau
>  MQ	+1436-06105	America/Martinique
>  MT	+3554+01431	Europe/Malta
>  MU	-2010+05730	Indian/Mauritius
> -MV	+0410+07330	Indian/Maldives
> +MV,TF	+0410+07330	Etc/GMT-5	Maldives, Kerguelen, St Paul I, Amsterdam I
>  MX	+1924-09909	America/Mexico_City	Central Time
>  MX	+2105-08646	America/Cancun	Eastern Standard Time - Quintana Roo
>  MX	+2058-08937	America/Merida	Central Time - Campeche, Yucatán
> @@ -247,43 +232,37 @@ MX	+2934-10425	America/Ojinaga	Mountain Time US - Chihuahua (US border)
>  MX	+2904-11058	America/Hermosillo	Mountain Standard Time - Sonora
>  MX	+3232-11701	America/Tijuana	Pacific Time US - Baja California
>  MX	+2048-10515	America/Bahia_Banderas	Central Time - Bahía de Banderas
> -MY	+0310+10142	Asia/Kuala_Lumpur	Malaysia (peninsula)
> -MY	+0133+11020	Asia/Kuching	Sabah, Sarawak
>  MZ,BI,BW,CD,MW,RW,ZM,ZW	-2558+03235	Africa/Maputo	Central Africa Time
>  NA	-2234+01706	Africa/Windhoek
>  NC	-2216+16627	Pacific/Noumea
>  NF	-2903+16758	Pacific/Norfolk
>  NG,AO,BJ,CD,CF,CG,CM,GA,GQ,NE	+0627+00324	Africa/Lagos	West Africa Time
>  NI	+1209-08617	America/Managua
> -NL	+5222+00454	Europe/Amsterdam
> -NO,SJ	+5955+01045	Europe/Oslo
>  NP	+2743+08519	Asia/Kathmandu
>  NR	-0031+16655	Pacific/Nauru
>  NU	-1901-16955	Pacific/Niue
>  NZ,AQ	-3652+17446	Pacific/Auckland	New Zealand time
>  NZ	-4357-17633	Pacific/Chatham	Chatham Islands
> -PA,KY	+0858-07932	America/Panama
> +PA,CA,KY	+0858-07932	America/Panama	EST - Panama, Cayman, ON (Atikokan), NU (Coral H)
>  PE	-1203-07703	America/Lima
> -PF	-1732-14934	Pacific/Tahiti	Society Islands
> +PF	-1732-14934	Etc/GMT+10	Society Islands
>  PF	-0900-13930	Pacific/Marquesas	Marquesas Islands
> -PF	-2308-13457	Pacific/Gambier	Gambier Islands
> -PG	-0930+14710	Pacific/Port_Moresby	Papua New Guinea (most areas)
> +PF	-2308-13457	Etc/GMT+9	Gambier Islands
>  PG	-0613+15534	Pacific/Bougainville	Bougainville
>  PH	+1435+12100	Asia/Manila
>  PK	+2452+06703	Asia/Karachi
>  PL	+5215+02100	Europe/Warsaw
>  PM	+4703-05620	America/Miquelon
>  PN	-2504-13005	Pacific/Pitcairn
> -PR	+182806-0660622	America/Puerto_Rico
> +PR,AG,CA,AI,AW,BL,BQ,CW,DM,GD,GP,KN,LC,MF,MS,SX,TT,VC,VG,VI	+182806-0660622	America/Puerto_Rico	AST
>  PS	+3130+03428	Asia/Gaza	Gaza Strip
>  PS	+313200+0350542	Asia/Hebron	West Bank
>  PT	+3843-00908	Europe/Lisbon	Portugal (mainland)
>  PT	+3238-01654	Atlantic/Madeira	Madeira Islands
>  PT	+3744-02540	Atlantic/Azores	Azores
> -PW	+0720+13429	Pacific/Palau
> +PW	+0720+13429	Etc/GMT-9
>  PY	-2516-05740	America/Asuncion
>  QA,BH	+2517+05132	Asia/Qatar
> -RE,TF	-2052+05528	Indian/Reunion	Réunion, Crozet, Scattered Islands
>  RO	+4426+02606	Europe/Bucharest
>  RS,BA,HR,ME,MK,SI	+4450+02030	Europe/Belgrade
>  RU	+5443+02030	Europe/Kaliningrad	MSK-01 - Kaliningrad
> @@ -314,12 +293,9 @@ RU	+4658+14242	Asia/Sakhalin	MSK+08 - Sakhalin Island
>  RU	+6728+15343	Asia/Srednekolymsk	MSK+08 - Sakha (E); North Kuril Is
>  RU	+5301+15839	Asia/Kamchatka	MSK+09 - Kamchatka
>  RU	+6445+17729	Asia/Anadyr	MSK+09 - Bering Sea
> -SA,KW,YE	+2438+04643	Asia/Riyadh
> -SB	-0932+16012	Pacific/Guadalcanal
> -SC	-0440+05528	Indian/Mahe
> +SB,FM	-0932+16012	Etc/GMT-11	Solomons, Pohnpei
>  SD	+1536+03232	Africa/Khartoum
> -SE	+5920+01803	Europe/Stockholm
> -SG	+0117+10351	Asia/Singapore
> +SG,MY	+0117+10351	Asia/Singapore	Singapore, peninsular Malaysia
>  SR	+0550-05510	America/Paramaribo
>  SS	+0451+03137	Africa/Juba
>  ST	+0020+00644	Africa/Sao_Tome
> @@ -327,8 +303,6 @@ SV	+1342-08912	America/El_Salvador
>  SY	+3330+03618	Asia/Damascus
>  TC	+2128-07108	America/Grand_Turk
>  TD	+1207+01503	Africa/Ndjamena
> -TF	-492110+0701303	Indian/Kerguelen	Kerguelen, St Paul Island, Amsterdam Island
> -TH,KH,LA,VN	+1345+10031	Asia/Bangkok	Indochina (most areas)
>  TJ	+3835+06848	Asia/Dushanbe
>  TK	-0922-17114	Pacific/Fakaofo
>  TL	-0833+12535	Asia/Dili
> @@ -336,13 +310,10 @@ TM	+3757+05823	Asia/Ashgabat
>  TN	+3648+01011	Africa/Tunis
>  TO	-210800-1751200	Pacific/Tongatapu
>  TR	+4101+02858	Europe/Istanbul
> -TT,AG,AI,BL,DM,GD,GP,KN,LC,MF,MS,VC,VG,VI	+1039-06131	America/Port_of_Spain
> -TV	-0831+17913	Pacific/Funafuti
>  TW	+2503+12130	Asia/Taipei
>  UA	+5026+03031	Europe/Kiev	Ukraine (most areas)
>  UA	+4837+02218	Europe/Uzhgorod	Transcarpathia
>  UA	+4750+03510	Europe/Zaporozhye	Zaporozhye and east Lugansk
> -UM	+1917+16637	Pacific/Wake	Wake Island
>  US	+404251-0740023	America/New_York	Eastern (most areas)
>  US	+421953-0830245	America/Detroit	Eastern - MI (most areas)
>  US	+381515-0854534	America/Kentucky/Louisville	Eastern - KY (Louisville area)
> @@ -362,7 +333,7 @@ US	+465042-1012439	America/North_Dakota/New_Salem	Central - ND (Morton rural)
>  US	+471551-1014640	America/North_Dakota/Beulah	Central - ND (Mercer)
>  US	+394421-1045903	America/Denver	Mountain (most areas)
>  US	+433649-1161209	America/Boise	Mountain - ID (south); OR (east)
> -US	+332654-1120424	America/Phoenix	MST - Arizona (except Navajo)
> +US,CA	+332654-1120424	America/Phoenix	MST - Arizona (except Navajo), Creston BC
>  US	+340308-1181434	America/Los_Angeles	Pacific
>  US	+611305-1495401	America/Anchorage	Alaska (most areas)
>  US	+581807-1342511	America/Juneau	Alaska - Juneau area
> @@ -378,6 +349,5 @@ UZ	+4120+06918	Asia/Tashkent	Uzbekistan (east)
>  VE	+1030-06656	America/Caracas
>  VN	+1045+10640	Asia/Ho_Chi_Minh	Vietnam (south)
>  VU	-1740+16825	Pacific/Efate
> -WF	-1318-17610	Pacific/Wallis
>  WS	-1350-17144	Pacific/Apia
>  ZA,LS,SZ	-2615+02800	Africa/Johannesburg
> -- 
> 2.27.0
> 

> diff --git a/Makefile b/Makefile
> index 8714c16..ce018ec 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -529,7 +529,7 @@ TZS_YEAR=	2050
>  TZS_CUTOFF_FLAG=	-c $(TZS_YEAR)
>  TZS=		to$(TZS_YEAR).tzs
>  TZS_NEW=	to$(TZS_YEAR)new.tzs
> -TZS_DEPS=	$(PRIMARY_YDATA) asctime.c localtime.c \
> +TZS_DEPS=	$(YDATA) asctime.c localtime.c \
>  			private.h tzfile.h zdump.c zic.c
>  # EIGHT_YARDS is just a yard short of the whole ENCHILADA.
>  EIGHT_YARDS = $(COMMON) $(DOCS) $(SOURCES) $(DATA) $(MISC) tzdata.zi
> diff --git a/NEWS b/NEWS
> index 6d1cd09..435a40f 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -26,6 +26,23 @@ Unreleased, experimental changes
>      (Thanks to P Chan, Michael Deckers, Alexander Krivenyshev and
>      Alois Treindl.)
>  
> +    Merge timezones whose timestamps agree since 1970, since pre-1970
> +    timestamps are out of scope.  This change does not affect
> +    post-1970 timestamps, and timezone historians who build with 'make
> +    PACKRATDATA=backzone' should see no changes to pre-1970 timestamps.
> +    When merging, keep the most-populous location's data, and move
> +    data for other locations to 'backzone' with a backward
> +    compatibility link in 'backward'.  Also, merge timezones with
> +    neither post-1970 clock changes nor alphabetic abbreviations into
> +    their Etc counterparts.  For example, move the Europe/Oslo data to
> +    'backzone' with a link in 'backward' from Europe/Berlin because
> +    the two timezones' timestamps agree since 1970; this change
> +    affects some pre-1966 timestamps in Europe/Oslo because Berlin and
> +    Oslo disagreed before 1966.  For another example, move the
> +    Asia/Aden data to 'backzone' with a link in 'backward' from
> +    Etc/GMT-3.  Affected entries range from Africa/Abidjan to
> +    Pacific/Yap.
> +
>    Changes to maintenance procedure
>  
>      The new file SECURITY covers how to report security-related bugs.
> diff --git a/backzone b/backzone
> index 6c77378..b58f4d8 100644
> --- a/backzone
> +++ b/backzone
> @@ -619,6 +619,8 @@ Zone America/Creston	-7:46:04 -	LMT	1884
>  Zone	America/Curacao	-4:35:47 -	LMT	1912 Feb 12 # Willemstad
>  			-4:30	-	-0430	1965
>  			-4:00	-	AST
> +Link	America/Curacao	America/Kralendijk
> +Link	America/Curacao	America/Lower_Princes
>  
>  # Dominica
>  Zone America/Dominica	-4:05:36 -	LMT	1911 Jul  1  0:01 # Roseau
> @@ -763,6 +765,9 @@ Zone	America/Nassau	-5:09:30 -	LMT	1912 Mar 2
>  # Trinidad and Tobago
>  Zone America/Port_of_Spain -4:06:04 -	LMT	1912 Mar 2
>  			-4:00	-	AST
> +Link America/Port_of_Spain America/Marigot
> +Link America/Port_of_Spain America/St_Barthelemy
> +Link America/Port_of_Spain America/Virgin
>  
>  # Argentina
>  # This entry was intended for the following areas, but has been superseded by
> @@ -1228,6 +1233,7 @@ Rule	Iceland	1967	only	-	Oct	29	 1:00s	0	-
>  Zone Atlantic/Reykjavik	-1:28	-	LMT	1908
>  			-1:00	Iceland	-01/+00	1968 Apr  7  1:00s
>  			 0:00	-	GMT
> +Link Atlantic/Reykjavik Iceland
>  
>  # South Georgia
>  Zone Atlantic/South_Georgia -2:26:08 -	LMT	1890 # Grytviken
> @@ -1520,6 +1526,7 @@ Zone	Europe/Oslo	0:43:00 -	LMT	1895 Jan  1
>  			1:00	C-Eur	CE%sT	1945 Apr  2  2:00
>  			1:00	Norway	CE%sT	1980
>  			1:00	EU	CE%sT
> +Link	Europe/Oslo	Arctic/Longyearbyen
>  
>  # Bosnia and Herzegovina
>  Zone	Europe/Sarajevo	1:13:40	-	LMT	1884
> @@ -1708,6 +1715,8 @@ Zone Pacific/Chuuk	-13:52:52 -	LMT	1844 Dec 31
>  			 10:00	-	+10	1941 Apr  1
>  			  9:00	-	+09	1945 Aug
>  			 10:00	-	+10
> +Link Pacific/Chuuk Pacific/Truk
> +Link Pacific/Chuuk Pacific/Yap
>  
>  # Tuvalu
>  Zone Pacific/Funafuti	11:56:52 -	LMT	1901
> @@ -1767,6 +1776,7 @@ Zone Pacific/Pohnpei	-13:27:08 -	LMT	1844 Dec 31	# Kolonia
>  			 10:00	-	+10	1941 Apr  1
>  			  9:00	-	+09	1945 Aug
>  			 11:00	-	+11
> +Link Pacific/Pohnpei Pacific/Ponape
>  
>  # Papua New Guinea
>  Zone Pacific/Port_Moresby 9:48:40 -	LMT	1880
> diff --git a/etcetera b/etcetera
> index 1dc7411..dc21c4d 100644
> --- a/etcetera
> +++ b/etcetera
> @@ -12,6 +12,8 @@
>  # Starting with POSIX 1003.1-2001, the entries below are all
>  # unnecessary as settings for the TZ environment variable.  E.g.,
>  # instead of TZ='Etc/GMT+4' one can use the POSIX setting TZ='<-04>+4'.
> +# However, some entries are needed if 'backward' is used:
> +# for example, the 'backward' file links Etc/GMT to Africa/Abidjan.
>  #
>  # Do not use a POSIX TZ setting like TZ='GMT+4', which is four hours
>  # behind GMT but uses the completely misleading abbreviation "GMT".
> diff --git a/theory.html b/theory.html
> index 5251c96..47a7b2d 100644
> --- a/theory.html
> +++ b/theory.html
> @@ -42,12 +42,13 @@ href="https://en.wikipedia.org/wiki/Unix_time">POSIX Epoch</a>
>  (1970-01-01 00:00:00 <a
>  href="https://en.wikipedia.org/wiki/Coordinated_Universal_Time"><abbr
>  title="Coordinated Universal Time">UTC</abbr></a>).
> -The database labels each timezone with a notable location and
> -records all known clock transitions for that location.
>  Although 1970 is a somewhat-arbitrary cutoff, there are significant
>  challenges to moving the cutoff earlier even by a decade or two, due
>  to the wide variety of local practices before computer timekeeping
>  became prevalent.
> +Most timezones correspond to a notable location and the database
> +records all known clock transitions for that location;
> +some timezones correspond instead to a fixed <abbr>UTC</abbr> offset.
>  </p>
>  
>  <p>
> @@ -68,7 +70,7 @@ time but differs from other timezones for some timestamps after 1970.
>  </p>
>  
>  <p>
> -Clock transitions before 1970 are recorded for each timezone,
> +Clock transitions before 1970 are recorded for location-based timezones,
>  because most systems support timestamps before 1970 and could
>  misbehave if data entries were omitted for pre-1970 transitions.
>  However, the database is not designed for and does not suffice for


-- 
Magnus Fromreide					+46-13 17 68 48
Tornhagsvägen 24, 2tr					magfr at lysator.liu.se
SE-582 37  LINKÖPING


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