proposed tz changes for Israel, Azerbaijan, etc.

Paul Eggert eggert at CS.UCLA.EDU
Tue Feb 22 23:30:39 UTC 2005 

Here are proposed changes to the tz database, spurred by Ephraim
Silverberg's report about Israel.

Changes to near-future time stamps:

 * Israel has revamped its daylight-saving rules this year, which
   means the unpatched tz database will mishandle time stamps starting
   April 1.  Thanks to Ephraim Silverberg for the detailed analysis
   (including Emacs source code!).

Changes to past time stamps:

 * Fix a glitch for time stamps in Azerbaijan on 1992-09-26.
   Thanks to Klaus Schmid for reporting the problem.

Changes to commentary:

 * Irish laws relating to time zones and daylight-saving time are available
   on the web.  Thanks to Joseph S. Myers for this info.

 * Pan Am used some unusual time zone designations for Midway in 1936.
   Thanks to Mark Brader for this info.

Changes to the tz-link.htm web page:

 * Mention Unicode's CLDR project.  Thanks to Mark Davis for mentioning
   CLDR.  Also, point at the current time zone table for CLDR, and update
   some obsolete references to ICU.

 * Mention some problems with numeric time zone abbreviations.
   Thanks to Peter Thoeny for mentioning the confusions in this area.

 * Use <abbr> and <code> more systematically.


===================================================================
RCS file: RCS/asia,v
retrieving revision 2005.5
retrieving revision 2005.5.0.2
diff -pu -r2005.5 -r2005.5.0.2
--- asia	2005/02/07 21:19:41	2005.5
+++ asia	2005/02/22 22:49:40	2005.5.0.2
@@ -107,7 +107,7 @@ Zone	Asia/Baku	3:19:24 -	LMT	1924 May  2
 			3:00	-	BAKT	1957 Mar    # Baku Time
 			4:00 RussiaAsia BAK%sT	1991 Mar 31 2:00s
 			3:00	1:00	BAKST	1991 Aug 30 # independence
-			3:00 RussiaAsia	AZ%sT	1992 Sep lastSun 2:00s
+			3:00 RussiaAsia	AZ%sT	1992 Sep lastSat 23:00
 			4:00	-	AZT	1996 # Azerbaijan time
 			4:00	EUAsia	AZ%sT	1997
 			4:00	Azer	AZ%sT
@@ -639,7 +639,8 @@ Rule	Zion	1988	only	-	Apr	 9	0:00	1:00	D
 Rule	Zion	1988	only	-	Sep	 3	0:00	0	S
 
 # From Ephraim Silverberg <ephraim at cs.huji.ac.il>
-# (1997-03-04, 1998-03-16, 1998-12-28, 2000-01-17, 2000-07-25, and 2004-12-22):
+# (1997-03-04, 1998-03-16, 1998-12-28, 2000-01-17, 2000-07-25, 2004-12-22,
+# and 2005-02-17):
 
 # According to the Office of the Secretary General of the Ministry of
 # Interior, there is NO set rule for Daylight-Savings/Standard time changes.
@@ -735,91 +736,74 @@ Rule	Zion	2003	only	-	Oct	 3	1:00	0	S
 Rule	Zion	2004	only	-	Apr	 7	1:00	1:00	D
 Rule	Zion	2004	only	-	Sep	22	1:00	0	S
 
-# Yesterday, the Knesset Interior Committee passed a proposed (originally
-# in March 2004) change to the Time Setting Law that would make the dates
-# for DST from 2005 and beyond so that DST starts on the night _after_ the
-# first night of the Passover holiday at midnight until midnight of the
-# Saturday night _before_ the fast of Yom Kippur.
-#
-# Those who can read Hebrew can view the proposal at:
-#
-#	ftp://ftp.cs.huji.ac.il/pub/tz/announcements/2005+.ps
-#
-# The proposal still has to be passed by the Knesset (three readings) for
-# it to become law....
-
-# From Paul Eggert (2004-12-22):
-# For now, guess that the rules proposed on 2004-12-20 will be adopted.
-# This is quite possibly wrong, but it is more likely than no DST at all.
-# I used Ed Reingold's cal-hebrew in GNU Emacs 21.3, along with code
-# written by Ephraim Silverberg, to generate this list.
-# Rule	NAME    FROM    TO      TYPE    IN      ON      AT      SAVE    LETTER/S
-Rule	Zion	2005	only	-	Apr	25	0:00	1:00	D
-Rule	Zion	2005	only	-	Oct	 9	0:00	0	S
-Rule	Zion	2006	only	-	Apr	14	0:00	1:00	D
-Rule	Zion	2006	only	-	Oct	 1	0:00	0	S
-Rule	Zion	2007	only	-	Apr	 4	0:00	1:00	D
-Rule	Zion	2007	only	-	Sep	16	0:00	0	S
-Rule	Zion	2008	only	-	Apr	21	0:00	1:00	D
-Rule	Zion	2008	only	-	Oct	 5	0:00	0	S
-Rule	Zion	2009	only	-	Apr	10	0:00	1:00	D
-Rule	Zion	2009	only	-	Sep	27	0:00	0	S
-Rule	Zion	2010	only	-	Mar	31	0:00	1:00	D
-Rule	Zion	2010	only	-	Sep	12	0:00	0	S
-Rule	Zion	2011	only	-	Apr	20	0:00	1:00	D
-Rule	Zion	2011	only	-	Oct	 2	0:00	0	S
-Rule	Zion	2012	only	-	Apr	 8	0:00	1:00	D
-Rule	Zion	2012	only	-	Sep	23	0:00	0	S
-Rule	Zion	2013	only	-	Mar	27	0:00	1:00	D
-Rule	Zion	2013	only	-	Sep	 8	0:00	0	S
-Rule	Zion	2014	only	-	Apr	16	0:00	1:00	D
-Rule	Zion	2014	only	-	Sep	28	0:00	0	S
-Rule	Zion	2015	only	-	Apr	 5	0:00	1:00	D
-Rule	Zion	2015	only	-	Sep	20	0:00	0	S
-Rule	Zion	2016	only	-	Apr	24	0:00	1:00	D
-Rule	Zion	2016	only	-	Oct	 9	0:00	0	S
-Rule	Zion	2017	only	-	Apr	12	0:00	1:00	D
-Rule	Zion	2017	only	-	Sep	24	0:00	0	S
-Rule	Zion	2018	only	-	Apr	 1	0:00	1:00	D
-Rule	Zion	2018	only	-	Sep	16	0:00	0	S
-Rule	Zion	2019	only	-	Apr	21	0:00	1:00	D
-Rule	Zion	2019	only	-	Oct	 6	0:00	0	S
-Rule	Zion	2020	only	-	Apr	10	0:00	1:00	D
-Rule	Zion	2020	only	-	Sep	27	0:00	0	S
-Rule	Zion	2021	only	-	Mar	29	0:00	1:00	D
-Rule	Zion	2021	only	-	Sep	12	0:00	0	S
-Rule	Zion	2022	only	-	Apr	17	0:00	1:00	D
-Rule	Zion	2022	only	-	Oct	 2	0:00	0	S
-Rule	Zion	2023	only	-	Apr	 7	0:00	1:00	D
-Rule	Zion	2023	only	-	Sep	24	0:00	0	S
-Rule	Zion	2024	only	-	Apr	24	0:00	1:00	D
-Rule	Zion	2024	only	-	Oct	 6	0:00	0	S
-Rule	Zion	2025	only	-	Apr	14	0:00	1:00	D
-Rule	Zion	2025	only	-	Sep	28	0:00	0	S
-Rule	Zion	2026	only	-	Apr	 3	0:00	1:00	D
-Rule	Zion	2026	only	-	Sep	20	0:00	0	S
-Rule	Zion	2027	only	-	Apr	23	0:00	1:00	D
-Rule	Zion	2027	only	-	Oct	10	0:00	0	S
-Rule	Zion	2028	only	-	Apr	12	0:00	1:00	D
-Rule	Zion	2028	only	-	Sep	24	0:00	0	S
-Rule	Zion	2029	only	-	Apr	 1	0:00	1:00	D
-Rule	Zion	2029	only	-	Sep	16	0:00	0	S
-Rule	Zion	2030	only	-	Apr	19	0:00	1:00	D
-Rule	Zion	2030	only	-	Oct	 6	0:00	0	S
-Rule	Zion	2031	only	-	Apr	 9	0:00	1:00	D
-Rule	Zion	2031	only	-	Sep	21	0:00	0	S
-Rule	Zion	2032	only	-	Mar	28	0:00	1:00	D
-Rule	Zion	2032	only	-	Sep	12	0:00	0	S
-Rule	Zion	2033	only	-	Apr	15	0:00	1:00	D
-Rule	Zion	2033	only	-	Oct	 2	0:00	0	S
-Rule	Zion	2034	only	-	Apr	 5	0:00	1:00	D
-Rule	Zion	2034	only	-	Sep	17	0:00	0	S
-Rule	Zion	2035	only	-	Apr	25	0:00	1:00	D
-Rule	Zion	2035	only	-	Oct	 7	0:00	0	S
-Rule	Zion	2036	only	-	Apr	13	0:00	1:00	D
-Rule	Zion	2036	only	-	Sep	28	0:00	0	S
-Rule	Zion	2037	only	-	Apr	 1	0:00	1:00	D
-Rule	Zion	2037	only	-	Sep	13	0:00	0	S
+# The proposed law agreed upon by the Knesset Interior Committee on
+# 2005-02-14 is that, for 2005 and beyond, DST starts at 02:00 the
+# last Friday before April 2nd (i.e. the last Friday in March or April
+# 1st itself if it falls on a Friday) and ends at 02:00 on the Saturday
+# night _before_ the fast of Yom Kippur.
+#
+# Those who can read Hebrew can view the announcement at:
+#
+#	ftp://ftp.cs.huji.ac.il/pub/tz/announcements/2005+beyond.ps
+
+# From Paul Eggert (2005-02-22):
+# I used Ephraim Silverberg's dst-israel.el program
+# <ftp://ftp.cs.huji.ac.il/pub/tz/software/dst-israel.el> (2005-02-20)
+# along with Ed Reingold's cal-hebrew in GNU Emacs 21.4,
+# to generate the transitions in this list.
+# (I replaced "lastFri" with "Fri>=26" by hand.)
+# The spring transitions below all correspond to the following Rule:
+#
+# Rule	Zion	2005	max	-	Mar	Fri>=26	2:00	1:00	D
+#
+# but older zic implementations (e.g., Solaris 8) do not support
+# "Fri>=26" to mean April 1 in years like 2005, so for now we list the
+# springtime transitions explicitly.
+
+# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
+Rule	Zion	2005	only	-	Apr	 1	2:00	1:00	D
+Rule	Zion	2005	only	-	Oct	 9	2:00	0	S
+Rule	Zion	2006	2010	-	Mar	Fri>=26	2:00	1:00	D
+Rule	Zion	2006	only	-	Oct	 1	2:00	0	S
+Rule	Zion	2007	only	-	Sep	16	2:00	0	S
+Rule	Zion	2008	only	-	Oct	 5	2:00	0	S
+Rule	Zion	2009	only	-	Sep	27	2:00	0	S
+Rule	Zion	2010	only	-	Sep	12	2:00	0	S
+Rule	Zion	2011	only	-	Apr	 1	2:00	1:00	D
+Rule	Zion	2011	only	-	Oct	 2	2:00	0	S
+Rule	Zion	2012	2015	-	Mar	Fri>=26	2:00	1:00	D
+Rule	Zion	2012	only	-	Sep	23	2:00	0	S
+Rule	Zion	2013	only	-	Sep	 8	2:00	0	S
+Rule	Zion	2014	only	-	Sep	28	2:00	0	S
+Rule	Zion	2015	only	-	Sep	20	2:00	0	S
+Rule	Zion	2016	only	-	Apr	 1	2:00	1:00	D
+Rule	Zion	2016	only	-	Oct	 9	2:00	0	S
+Rule	Zion	2017	2021	-	Mar	Fri>=26	2:00	1:00	D
+Rule	Zion	2017	only	-	Sep	24	2:00	0	S
+Rule	Zion	2018	only	-	Sep	16	2:00	0	S
+Rule	Zion	2019	only	-	Oct	 6	2:00	0	S
+Rule	Zion	2020	only	-	Sep	27	2:00	0	S
+Rule	Zion	2021	only	-	Sep	12	2:00	0	S
+Rule	Zion	2022	only	-	Apr	 1	2:00	1:00	D
+Rule	Zion	2022	only	-	Oct	 2	2:00	0	S
+Rule	Zion	2023	2032	-	Mar	Fri>=26	2:00	1:00	D
+Rule	Zion	2023	only	-	Sep	24	2:00	0	S
+Rule	Zion	2024	only	-	Oct	 6	2:00	0	S
+Rule	Zion	2025	only	-	Sep	28	2:00	0	S
+Rule	Zion	2026	only	-	Sep	20	2:00	0	S
+Rule	Zion	2027	only	-	Oct	10	2:00	0	S
+Rule	Zion	2028	only	-	Sep	24	2:00	0	S
+Rule	Zion	2029	only	-	Sep	16	2:00	0	S
+Rule	Zion	2030	only	-	Oct	 6	2:00	0	S
+Rule	Zion	2031	only	-	Sep	21	2:00	0	S
+Rule	Zion	2032	only	-	Sep	12	2:00	0	S
+Rule	Zion	2033	only	-	Apr	 1	2:00	1:00	D
+Rule	Zion	2033	only	-	Oct	 2	2:00	0	S
+Rule	Zion	2034	2037	-	Mar	Fri>=26	2:00	1:00	D
+Rule	Zion	2034	only	-	Sep	17	2:00	0	S
+Rule	Zion	2035	only	-	Oct	 7	2:00	0	S
+Rule	Zion	2036	only	-	Sep	28	2:00	0	S
+Rule	Zion	2037	only	-	Sep	13	2:00	0	S
 
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Asia/Jerusalem	2:20:56 -	LMT	1880
===================================================================
RCS file: RCS/australasia,v
retrieving revision 2003.4
retrieving revision 2003.4.0.1
diff -pu -r2003.4 -r2003.4.0.1
--- australasia	2003/10/06 13:32:20	2003.4
+++ australasia	2005/02/22 22:51:26	2003.4.0.1
@@ -434,6 +434,17 @@ Zone Pacific/Johnston	-10:00	-	HST
 # uninhabited
 
 # Midway
+#
+# From Mark Brader (2005-01-23):
+# [Fallacies and Fantasies of Air Transport History, by R.E.G. Davies,
+# published 1994 by Paladwr Press, McLean, VA, USA; ISBN 0-9626483-5-3]
+# reproduced a Pan American Airways timeables from 1936, for their weekly
+# "Orient Express" flights between San Francisco and Manila, and connecting
+# flights to Chicago and the US East Coast.  As it uses some time zone
+# designations that I've never seen before:....
+# Fri. 6:30A Lv. HONOLOLU (Pearl Harbor), H.I.   H.L.T. Ar. 5:30P Sun.
+#  "   3:00P Ar. MIDWAY ISLAND . . . . . . . . . M.L.T. Lv. 6:00A  "
+#
 Zone Pacific/Midway	-11:49:28 -	LMT	1901
 			-11:00	-	NST	1956 Jun  3
 			-11:00	1:00	NDT	1956 Sep  2
===================================================================
RCS file: RCS/europe,v
retrieving revision 2005.3
retrieving revision 2005.3.0.1
diff -pu -r2005.3 -r2005.3.0.1
--- europe	2005/01/17 23:36:17	2005.3
+++ europe	2005/02/22 22:50:34	2005.3.0.1
@@ -255,6 +255,35 @@
 #   "Timeball on the ballast office is down.  Dunsink time."
 #   -- James Joyce, Ulysses
 
+# From Joseph S. Myers (2005-01-26):
+# Irish laws are available online at www.irishstatutebook.ie.  These include 
+# various relating to legal time, for example:
+# 
+# ZZA13Y1923.html ZZA12Y1924.html ZZA8Y1925.html ZZSIV20PG1267.html
+# 
+# ZZSI71Y1947.html ZZSI128Y1948.html ZZSI23Y1949.html ZZSI41Y1950.html
+# ZZSI27Y1951.html ZZSI73Y1952.html
+# 
+# ZZSI11Y1961.html ZZSI232Y1961.html ZZSI182Y1962.html
+# ZZSI167Y1963.html ZZSI257Y1964.html ZZSI198Y1967.html
+# ZZA23Y1968.html ZZA17Y1971.html
+# 
+# ZZSI67Y1981.html ZZSI212Y1982.html ZZSI45Y1986.html
+# ZZSI264Y1988.html ZZSI52Y1990.html ZZSI371Y1992.html
+# ZZSI395Y1994.html ZZSI484Y1997.html ZZSI506Y2001.html
+#
+# [These are all relative to the root, e.g., the first is
+# <http://www.irishstatutebook.ie/ZZA13Y1923.html>.]
+# 
+# (These are those I found, but there could be more.  In any case these 
+# should allow various updates to the comments in the europe file to cover 
+# the laws applicable in Ireland.)
+# 
+# (Note that the time in the Republic of Ireland since 1968 has been defined 
+# in terms of standard time being GMT+1 with a period of winter time when it 
+# is GMT, rather than standard time being GMT with a period of summer time 
+# being GMT+1.)
+
 # From Paul Eggert (1999-03-28):
 # Clive Feather (<news:859845706.26043.0 at office.demon.net>, 1997-03-31)
 # reports that Folkestone (Cheriton) Shuttle Terminal uses Concession Time
===================================================================
RCS file: RCS/tz-link.htm,v
retrieving revision 2005.3
retrieving revision 2005.3.0.1
diff -pu -r2005.3 -r2005.3.0.1
--- tz-link.htm	2005/01/17 23:36:19	2005.3
+++ tz-link.htm	2005/02/22 23:10:33	2005.3.0.1
@@ -36,9 +36,9 @@ This database (often called <code>tz</co
 is used by several implementations,
 including
 <a href="http://www.gnu.org/software/libc/">the
-<acronym title="GNU's Not Unix">GNU</acronym>
+<abbr title="GNU's Not Unix">GNU</abbr>
 C Library</a> used in
-<a href="http://www.linux.org/"><acronym>GNU</acronym>/Linux</a>,
+<a href="http://www.linux.org/"><abbr>GNU</abbr>/Linux</a>,
 <a href="http://www.freebsd.org/">FreeBSD</a>,
 <a href="http://www.netbsd.org/">NetBSD</a>,
 <a href="http://www.openbsd.org/">OpenBSD</a>,
@@ -80,7 +80,7 @@ where <code><var>C</var></code> is the c
 similarly, the data are in <code>tzdata<var>D</var>.tar.gz</code>,
 where <code><var>D</var></code> is the data's version.
 The following shell commands download
-these files to a <acronym>GNU</acronym>/Linux or similar host;
+these files to a <abbr>GNU</abbr>/Linux or similar host;
 see the downloaded
 <code>README</code> file for what to do next.</p>
 <pre style="margin-left: 2em"><code><a href="http://www.gnu.org/software/wget/">wget</a> 'ftp://elsie.nci.nih.gov/pub/tz*.tar.gz'
@@ -164,7 +164,7 @@ Timezone Converter</a> describes a progr
 <code>tz</code> source into iCalendar-compatible VTIMEZONE files.
 Vzic is freely
 available under the <a
-href="http://www.gnu.org/copyleft/gpl.html"><acronym>GNU</acronym>
+href="http://www.gnu.org/copyleft/gpl.html"><abbr>GNU</abbr>
 General Public License (<abbr
 title="General Public License">GPL</abbr>)</a>.</li>
 <li><a
@@ -180,7 +180,7 @@ transition in the <code>tz</code> databa
 <li><a href="http://oss.software.ibm.com/icu/"><abbr
 title="International Components for Unicode">ICU</abbr></a>
 contains a C/C++ library for internationalization that
-has a compiler from <samp>tz</samp> source
+has a compiler from <code>tz</code> source
 into an <abbr>ICU</abbr>-specific format.
 <abbr>ICU</abbr> is freely available under a
 <abbr title="Berkeley Software Distribution">BSD</abbr>-style license.</li>
@@ -198,18 +198,18 @@ It is freely available under a <abbr>BSD
 <h2>Other <code>tz</code> binary file readers</h2>
 <ul>
 <li>The <a
-href="http://www.gnu.org/software/libc/"><acronym>GNU</acronym> C
+href="http://www.gnu.org/software/libc/"><abbr>GNU</abbr> C
 Library</a>
 has an independent, thread-safe implementation of
 a <code>tz</code> binary file reader.
 This library is freely available under the
 <a href="http://www.gnu.org/copyleft/lesser.html">
-<acronym>GNU</acronym> Lesser General Public License
+<abbr>GNU</abbr> Lesser General Public License
 (<abbr title="Lesser General Public License">LGPL</abbr>)</a>,
-and is widely used in <acronym>GNU</acronym>/Linux systems.</li>
+and is widely used in <abbr>GNU</abbr>/Linux systems.</li>
 <li><a href="http://www.bmsi.com/java/#TZ">ZoneInfo.java</a>
 is a <code>tz</code> binary file reader written in Java.
-It is freely available under the <acronym>GNU</acronym>
+It is freely available under the <abbr>GNU</abbr>
 <abbr>LGPL</abbr>.</li>
 <li><a href="http://s.keim.free.fr/tz/doc.html">Python time zones</a>
 is a <code>tz</code> binary file reader written in Python.
@@ -218,7 +218,7 @@ It is freely available under a <abbr>BSD
 <h2>Other <code>tz</code>-based time zone conversion software</h2>
 <ul>
 <li><a href="http://java.sun.com/">Sun Java</a> releases since 1.4
-contain a copy of a subset of a recent <samp>tz</samp> database in a
+contain a copy of a subset of a recent <code>tz</code> database in a
 Java-specific format.</li>
 <li><a
 href="http://www1.tip.nl/~t876506/AboutTimeZonesHC.html">HyperCard
@@ -287,7 +287,7 @@ zone boundaries for multizone countries<
 boundaries between time zones within countries.</li>
 <li>Manifold.net's <a
 href="http://www.manifold.net/download/freemaps.html">Free Maps and
-<acronym title="Geographic Information Systems">GIS</acronym>
+<abbr title="Geographic Information Systems">GIS</abbr>
 Data</a> includes a Manifold-format map of
 world time zone boundaries distributed under the
 <abbr>GPL</abbr>.</li>
@@ -413,8 +413,8 @@ Times</a> explains more abstruse astrono
 <abbr title="Barycentric Dynamic Time">TDB</abbr>.</li>
 <li>The <a href="http://www.iau.org/"><abbr
 title="International Astronomical Union">IAU</abbr></a>'s <a
-href="http://www.iau-sofa.rl.ac.uk/"><acronym
-title="Standards Of Fundamental Astronomy">SOFA</acronym></a>
+href="http://www.iau-sofa.rl.ac.uk/"><abbr
+title="Standards Of Fundamental Astronomy">SOFA</abbr></a>
 initiative publishes Fortran
 code for converting among time scales like
 <abbr title="International Atomic Time">TAI</abbr>,
@@ -484,13 +484,21 @@ protocols.</li>
 Best of Dates, the Worst of Dates</a> covers many problems encountered
 by software developers when handling dates and time stamps.</li>
 <li><a
-href="http://oss.software.ibm.com/cvs/icu/~checkout~/locale/docs/design/formatting/time_zone_localization.html">Time
-Zone Localization</a> is a proposed mechanism for localizing time zone
-labels and abbreviations; for example, one might use it to specify
+href="http://ibm.com/software/globalization/icu"><abbr
+title="International Components for Unicode">ICU</abbr></a> contains a
+mechanism for localizing time zone
+labels and abbreviations; for example, one can use it to specify
 Russian translations for "Eastern European Summer Time",
 "<abbr title="Eastern European Summer Time">EEST</abbr>",
-and <code>Europe/Bucharest</code>.</li>
-<li> Alphabetic time zone abbreviations should not be used as unique
+and <code>Europe/Bucharest</code>.
+This mechanism is part of the
+<a href="http://unicode.org/cldr/">Unicode
+<abbr title="Common Locale Data Repository">CLDR</abbr> Project</a>;
+for example, the <a
+href="http://www.unicode.org/cldr/data/diff/by_type/dates_timeZoneNames.html">By-Type
+Chart for //ldml/dates/timeZoneNames/&hellip;</a>
+shows values for time zone names in many locales.</li>
+<li>Alphabetic time zone abbreviations should not be used as unique
 identifiers for <abbr>UTC</abbr> offsets as they are ambiguous in
 practice. For example, "<abbr>EST</abbr>" denotes 5 hours behind
 <abbr>UTC</abbr> in English-speaking North America, but it denotes 10
@@ -501,6 +509,21 @@ French-speaking North Americans prefer
 database contains English abbreviations for all time stamps but in
 many cases these are merely inventions of the database
 maintainers.</li>
+<li>Numeric time zone abbreviations typically count hours east of
+<abbr>UTC</abbr>, e.g., <code>+09</code> for Japan and
+<code>-10</code> for Hawaii. However, the <abbr>POSIX</abbr>
+<code>TZ</code> environment variable uses the opposite convention. For
+example, one might use <code>TZ="JST-9"</code> and
+<code>TZ="HST10"</code> for Japan and Hawaii, respectively. If the
+<code>tz</code> database is available, it is usually better to use
+settings like <code>TZ="Asia/Tokyo"</code> and
+<code>TZ="Pacific/Honolulu"</code> instead, as this should avoid
+confusion, handle old timestamps better, and insulate you better from
+any future changes to the rules. One should never set
+<abbr>POSIX</abbr> <code>TZ</code> to a value like
+<code>"GMT-9"</code>, though, since this would falsely claim that
+local time is nine hours ahead of <abbr>UTC</abbr> and the time zone
+is called "<abbr>GMT</abbr>".</li>
 </ul>
 <h2>Related indexes</h2>
 <ul>

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