From a36efc81178675a45aa64e1047a8c1c45b2059aa Mon Sep 17 00:00:00 2001
From: Tim Parenti <tim@timtimeonline.com>
Date: Tue, 9 Apr 2024 08:16:22 -0700
Subject: [WORK-IN-PROGRESS v1.3] Improve data for Portugal and former
 possessions

Based on a close reading of old Portuguese legislation,
fix timestamps for Africa/Maputo before 1909, for
Atlantic/Azores before 1994, for Atlantic/Madeira before 1987,
for Europe/Lisbon before 1986, and for Asia/Dili before 1912.
* asia (Asia/Dili): 1912 transition is at 00:00 UT, not local time.
* europe (Port, Europe/Lisbon, Atlantic/Azores, Atlantic/Madeira):
Simplify and make several changes to follow decrees.
---
 NEWS     |   4 +-
 africa   |   9 +-
 asia     |   9 +-
 backzone |  13 +--
 europe   | 308 +++++++++++++++++++++++++++++++++++++++++++++----------
 5 files changed, 270 insertions(+), 73 deletions(-)

diff --git a/NEWS b/NEWS
index 0d6a1513..087b2763 100644
--- a/NEWS
+++ b/NEWS
@@ -17,7 +17,9 @@ Unreleased, experimental changes
     Rearguard form still avoids %z, to support obsolescent parsers.
 
     Some transitions for Portugal and possessions have been changed.
-    This affects timestamps for Africa/Maputo before 1909.
+    This affects timestamps for Africa/Maputo before 1909, for
+    Atlantic/Azores before 1994, for Atlantic/Madeira before 1987,
+    for Europe/Lisbon before 1986, and for Asia/Dili before 1912.
 
     Asia/Almaty has been removed from zonenow.tab as it now agrees
     with Asia/Tashkent for future timestamps, due to Kazakhstan's
diff --git a/africa b/africa
index 695d66ed..cb3f2344 100644
--- a/africa
+++ b/africa
@@ -105,11 +105,11 @@ Zone	Africa/Algiers	0:12:12 -	LMT	1891 Mar 16
 #
 # From Paul Eggert (2018-02-16):
 # Shanks gives 1907 for the transition to +02.
-# For now, ignore that and follow the 1911-05-26 Portuguese decree
+# For now, ignore that and follow the 1911-05-24 Portuguese decree
 # (see Europe/Lisbon).
 #
 # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
-Zone Atlantic/Cape_Verde -1:34:04 -	LMT	1912 Jan 01  2:00u # Praia
+Zone Atlantic/Cape_Verde -1:34:04 -	LMT	1912 Jan  1  2:00u # Praia
 			-2:00	-	%z	1942 Sep
 			-2:00	1:00	%z	1945 Oct 15
 			-2:00	-	%z	1975 Nov 25  2:00
@@ -345,10 +345,7 @@ Zone	Africa/Cairo	2:05:09 -	LMT	1900 Oct
 
 # Guinea-Bissau
 #
-# From Paul Eggert (2018-02-16):
-# Shanks gives 1911-05-26 for the transition to WAT,
-# evidently confusing the date of the Portuguese decree
-# (see Europe/Lisbon) with the date that it took effect.
+# For timestamps before independence see Europe/Lisbon commentary.
 #
 # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
 Zone	Africa/Bissau	-1:02:20 -	LMT	1912 Jan  1  1:00u
diff --git a/asia b/asia
index 0766bb1e..4e30cade 100644
--- a/asia
+++ b/asia
@@ -1210,6 +1210,13 @@ Zone	Asia/Tbilisi	2:59:11 -	LMT	1880
 
 # East Timor
 
+# From Tim Parenti (2024-03-XXX):
+# The 1912-01-01 transition occurred at 00:00 new time, per the 1911-05-24
+# Portuguese decree (see Europe/Lisbon).  A provision in article 5(c) of the
+# decree prescribed that Timor "will keep counting time in harmony with
+# neighboring foreign colonies, [for] as long as they do not adopt the time
+# that belongs to them in [the Washington Convention] system."
+
 # See Indonesia for the 1945 transition.
 
 # From João Carrascalão, brother of the former governor of East Timor, in
@@ -1233,7 +1240,7 @@ Zone	Asia/Tbilisi	2:59:11 -	LMT	1880
 # midnight on Saturday, September 16.
 
 # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
-Zone	Asia/Dili	8:22:20 -	LMT	1912 Jan  1
+Zone	Asia/Dili	8:22:20 -	LMT	1911 Dec 31 16:00u
 			8:00	-	%z	1942 Feb 21 23:00
 			9:00	-	%z	1976 May  3
 			8:00	-	%z	2000 Sep 17  0:00
diff --git a/backzone b/backzone
index f4525034..87ed7e6e 100644
--- a/backzone
+++ b/backzone
@@ -346,10 +346,7 @@ Zone	Africa/Lome	0:04:52 -	LMT	1893
 
 # Angola
 #
-# From Paul Eggert (2018-02-16):
-# Shanks gives 1911-05-26 for the transition to WAT,
-# evidently confusing the date of the Portuguese decree
-# (see Europe/Lisbon) with the date that it took effect.
+# For timestamps before independence see Europe/Lisbon commentary.
 #
 Zone	Africa/Luanda	0:52:56	-	LMT	1892
 			0:52:04	-	LMT	1911 Dec 31 23:00u # Luanda MT?
@@ -1086,10 +1083,10 @@ Zone	Asia/Muscat	3:54:24 -	LMT	1920
 			4:00	-	+04
 
 # India
-# From Paul Eggert (2014-08-11), after a heads-up from Stephen Colebourne:
-# According to a Portuguese decree (1911-05-26)
-# https://dre.pt/pdf1sdip/1911/05/12500/23132313.pdf
-# Portuguese India switched to UT +05 on 1912-01-01.
+# From Tim Parenti (2024-03-XXX), per Paul Eggert (2014-08-11), after a
+# heads-up from Stephen Colebourne:
+# According to a Portuguese decree (1911-05-24), Portuguese India switched to
+# UT +05 on 1912-01-01 (see Europe/Lisbon).
 #Zone	Asia/Panaji	[not enough info to complete]
 
 # Cambodia
diff --git a/europe b/europe
index f19c4563..591f9abf 100644
--- a/europe
+++ b/europe
@@ -2063,10 +2063,39 @@ Zone	Europe/Warsaw	1:24:00 -	LMT	1880
 
 # Portugal
 
-# From Paul Eggert (2014-08-11), after a heads-up from Stephen Colebourne:
-# According to a Portuguese decree (1911-05-26)
-# https://dre.pt/application/dir/pdf1sdip/1911/05/12500/23132313.pdf
-# Lisbon was at -0:36:44.68, but switched to GMT on 1912-01-01 at 00:00.
+# From Tim Parenti (2024-03-XXX), per Alois Treindl (2021-02-07) and Michael
+# Deckers (2021-02-10):
+# http://oal.ul.pt/documentos/2018/01/hl1911a2018.pdf/
+# The Astronomical Observatory of Lisbon has published a list detailing the
+# historical transitions in legal time within continental Portugal.  It
+# directly references many decrees and ordinances which are, in turn,
+# referenced below.  They can be viewed in the public archives of the Diário da
+# República (until 1976-04-09 known as the Diário do Govêrno) at
+# https://dre.pt/ (in Portuguese).
+#
+# Most of the Rules below, have been updated simply to match the Observatory's
+# listing for continental (mainland) Portugal.  Although there are over 50
+# referenced decrees and ordinances, only the handful with comments below have
+# been verified against the text, typically to provide additional confidence
+# wherever dates provided by Whitman and Shanks & Pottenger had disagreed.
+# See further below for the Azores and Madeira.
+
+# From Tim Parenti (2024-03-XXX), per Paul Eggert (2014-08-11), after a
+# heads-up from Stephen Colebourne:
+# According to a 1911-05-24 Portuguese decree, Lisbon was at -0:36:44.68, but
+# switched to GMT on 1912-01-01 at 00:00.
+# https://dre.pt/dr/detalhe/decreto/593090
+# https://dre.pt/application/conteudo/593090
+# The decree made legal time throughout Portugal and her possessions
+# "subordinate to the Greenwich meridian, according to the principle adopted at
+# the Washington Convention in 1884" and eliminated the "difference of five
+# minutes between the internal and external clocks of railway stations".
+#
+# The decree was gazetted in the 1911-05-30 issue of Diário do Govêrno, and is
+# considered to be dated 1911-05-24 by that issue's summary; however, the text
+# of the decree itself is dated 1911-05-26.  The Diário da República website
+# notes the discrepancy, but later laws and the Observatory all seem to refer
+# to this decree by the 1911-05-24 date.
 #
 # From Michael Deckers (2018-02-15):
 # article 5 [of the 1911 decree; Deckers's translation] ...:
@@ -2074,37 +2103,62 @@ Zone	Europe/Warsaw	1:24:00 -	LMT	1880
 # according to the 2nd article, the civil day January 1, 1912 begins,
 # all clocks therefore having to be advanced or set back correspondingly ...
 
-# From Rui Pedro Salgueiro (1992-11-12):
-# Portugal has recently (September, 27) changed timezone
-# (from WET to MET or CET) to harmonize with EEC.
-#
-# Martin Bruckmann (1996-02-29) reports via Peter Ilieve
-# that Portugal is reverting to 0:00 by not moving its clocks this spring.
-# The new Prime Minister was fed up with getting up in the dark in the winter.
-#
-# From Paul Eggert (1996-11-12):
-# IATA SSIM (1991-09) reports several 1991-09 and 1992-09 transitions
-# at 02:00u, not 01:00u.  Assume that these are typos.
-# IATA SSIM (1991/1992) reports that the Azores were at -1:00.
-# IATA SSIM (1993-02) says +0:00; later issues (through 1996-09) say -1:00.
-# Guess that the Azores changed to EU rules in 1992 (since that's when Portugal
-# harmonized with EU rules), and that they stayed +0:00 that winter.
-#
 # Rule	NAME	FROM	TO	-	IN	ON	AT	SAVE	LETTER/S
-# DSH writes that despite Decree 1,469 (1915), the change to the clocks was not
-# done every year, depending on what Spain did, because of railroad schedules.
-# Go with Shanks & Pottenger.
+# From Tim Parenti (2024-03-XXX), per Paul Eggert (1999-01-30):
+# DSH writes in their history that Decreto 1469 of 1915-03-30 established
+# summer time and that, "despite" this, the change to the clocks was not done
+# every year, depending on what Spain did, because of railroad schedules.
+# In fact, that decree had nothing to do with DST; rather, it regulated the
+# sending of time signals.  But we do see linkage to Spain in the 1920s below.
+# https://dre.pt/dr/detalhe/decreto/1469-1915-285721
+# https://dre.pt/application/conteudo/285721
+#
+# According to the Observatory, standard time was first advanced by Decreto
+# 2433 of 1916-06-09 and restored by Decreto 2712 of 1916-10-28.  While Whitman
+# gives 1916-10-31 for the latter transition, Shanks & Pottenger agrees more
+# closely with the decree, which stated that its provision "will start sixty
+# minutes after the end of 31 October, according to the current time," i.e.,
+# 01:00 on 1 November.
+# https://dre.pt/dr/detalhe/decreto/2433-1916-267192
+# https://dre.pt/application/conteudo/267192
+# https://dre.pt/dr/detalhe/decreto/2712-1916-590937
+# https://dre.pt/application/conteudo/590937
 Rule	Port	1916	only	-	Jun	17	23:00	1:00	S
-# Whitman gives 1916 Oct 31; go with Shanks & Pottenger.
 Rule	Port	1916	only	-	Nov	 1	 1:00	0	-
-Rule	Port	1917	only	-	Feb	28	23:00s	1:00	S
-Rule	Port	1917	1921	-	Oct	14	23:00s	0	-
-Rule	Port	1918	only	-	Mar	 1	23:00s	1:00	S
-Rule	Port	1919	only	-	Feb	28	23:00s	1:00	S
-Rule	Port	1920	only	-	Feb	29	23:00s	1:00	S
-Rule	Port	1921	only	-	Feb	28	23:00s	1:00	S
+# From Tim Parenti (2024-03-XXX):
+# Article 7 of Decreto 2922 of 1916-12-30 stated that "the legal time will be
+# advanced by sixty minutes from 1 March to 31 October."  Per Article 15, this
+# came into force from 1917-01-01.  Just before the first fall back, Decreto
+# 3446 of 1917-10-11 changed the annual end date to 14 October.
+# https://dre.pt/dr/detalhe/decreto/2922-1916-261894
+# https://dre.pt/application/conteudo/261894
+# https://dre.pt/dr/detalhe/decreto/3446-1917-495161
+# https://dre.pt/application/conteudo/495161
+# This annual change was revoked by Decreto 8038 of 1922-02-18.
+# https://dre.pt/dr/detalhe/decreto/8038-1922-569751
+# https://dre.pt/application/conteudo/569751
+Rule	Port	1917	1921	-	Mar	 1	 0:00	1:00	S
+Rule	Port	1917	1921	-	Oct	14	24:00	0	-
+# From Tim Parenti (2024-03-XXX):
+# Decreto 9592 of 1924-04-14 noted that "France maintains the advance of legal
+# time in the summer and Spain has now adopted it for the first time" and
+# considered "that the absence of similar measures would cause serious
+# difficulties for international rail connections with consequent repercussions
+# on domestic service hours..." along with "inconvenient analogues...for postal
+# and telegraph services."  Summer time would be in effect from 17 April to 4
+# October, with the spring change explicitly specified by bringing clocks
+# forward from 16 April 23:00.
+# https://dre.pt/dr/detalhe/decreto/9592-1924-652133
+# https://dre.pt/application/conteudo/652133
+#
+# Decreto 10700, issued 1925-04-16, noted that Spain had not continued summer
+# time, declared that "the current legal hour prior to 17 April remains
+# unchanged from that day forward", and revoked legislation to the contrary,
+# just a day before summer time would have otherwise resumed.
+# https://dre.pt/dr/detalhe/decreto/10700-1925-437826
+# https://dre.pt/application/conteudo/437826
 Rule	Port	1924	only	-	Apr	16	23:00s	1:00	S
-Rule	Port	1924	only	-	Oct	14	23:00s	0	-
+Rule	Port	1924	only	-	Oct	 4	23:00s	0	-
 Rule	Port	1926	only	-	Apr	17	23:00s	1:00	S
 Rule	Port	1926	1929	-	Oct	Sat>=1	23:00s	0	-
 Rule	Port	1927	only	-	Apr	 9	23:00s	1:00	S
@@ -2116,6 +2170,8 @@ Rule	Port	1931	1932	-	Oct	Sat>=1	23:00s	0	-
 Rule	Port	1932	only	-	Apr	 2	23:00s	1:00	S
 Rule	Port	1934	only	-	Apr	 7	23:00s	1:00	S
 # Whitman gives 1934 Oct 5; go with Shanks & Pottenger.
+# Note: The 1935 law specified 10-06 00:00, not 10-05 24:00, but the following
+# is equivalent and more succinct.
 Rule	Port	1934	1938	-	Oct	Sat>=1	23:00s	0	-
 # Shanks & Pottenger give 1935 Apr 30; go with Whitman.
 Rule	Port	1935	only	-	Mar	30	23:00s	1:00	S
@@ -2126,10 +2182,19 @@ Rule	Port	1938	only	-	Mar	26	23:00s	1:00	S
 Rule	Port	1939	only	-	Apr	15	23:00s	1:00	S
 # Whitman gives 1939 Oct 7; go with Shanks & Pottenger.
 Rule	Port	1939	only	-	Nov	18	23:00s	0	-
+# From Tim Parenti (2024-03-XXX):
+# Portaria 9465 of 1940-02-17 advanced clocks from Saturday 1940-02-24 23:00.
+# The clocks were restored by Portaria 9658, issued Monday 1940-10-07,
+# effective from 24:00 that very night, which agrees with Shanks & Pottenger;
+# Whitman gives Saturday 1940-10-05 instead.
+# https://dre.pt/dr/detalhe/portaria/9465-1940-189096
+# https://dre.pt/application/conteudo/189096
+# https://dre.pt/dr/detalhe/portaria/9658-1940-196729
+# https://dre.pt/application/conteudo/196729
 Rule	Port	1940	only	-	Feb	24	23:00s	1:00	S
-# Shanks & Pottenger give 1940 Oct 7; go with Whitman.
-Rule	Port	1940	1941	-	Oct	 5	23:00s	0	-
+Rule	Port	1940	only	-	Oct	 7	23:00s	0	-
 Rule	Port	1941	only	-	Apr	 5	23:00s	1:00	S
+Rule	Port	1941	only	-	Oct	 5	23:00s	0	-
 Rule	Port	1942	1945	-	Mar	Sat>=8	23:00s	1:00	S
 Rule	Port	1942	only	-	Apr	25	22:00s	2:00	M # Midsummer
 Rule	Port	1942	only	-	Aug	15	22:00s	1:00	S
@@ -2139,35 +2204,133 @@ Rule	Port	1943	1945	-	Aug	Sat>=25	22:00s	1:00	S
 Rule	Port	1944	1945	-	Apr	Sat>=21	22:00s	2:00	M
 Rule	Port	1946	only	-	Apr	Sat>=1	23:00s	1:00	S
 Rule	Port	1946	only	-	Oct	Sat>=1	23:00s	0	-
-# Whitman says DST was not observed in 1950; go with Shanks & Pottenger.
-# Whitman gives Oct lastSun for 1952 on; go with Shanks & Pottenger.
-Rule	Port	1947	1965	-	Apr	Sun>=1	 2:00s	1:00	S
+# From Tim Parenti (2024-03-XXX), per Alois Treindl (2021-02-07):
+# The Astronomical Observatory of Lisbon cites Portaria 11767 of 1947-03-28 for
+# 1947 and Portaria 12286 of 1948-02-19 for 1948.
+# https://dre.pt/dr/detalhe/portaria/11767-1947-414787
+# https://dre.pt/application/conteudo/414787
+# https://dre.pt/dr/detalhe/portaria/12286-1948-152953
+# https://dre.pt/application/conteudo/152953
+#
+# Although the latter ordinance explicitly had the 1948-10-03 transition
+# scheduled for 02:00 rather than 03:00 as had been used in 1947, Decreto-Lei
+# 37048 of 1948-09-07 recognized "that it is advisable to definitely set...the
+# 'summer time' regime", and fixed the fall transition at 03:00 moving forward.
+# https://dre.pt/dr/detalhe/decreto-lei/37048-1948-373810
+# https://dre.pt/application/conteudo/373810
+# While the Observatory only cites this act for 1949-1965 and not for 1948, it
+# does not appear to have had any provision delaying its effect, so assume that
+# it overrode the prior ordinance for 1948-10-03.
+#
+# Whitman says DST was not observed in 1950 and gives Oct lastSun for 1952 on.
+# The Observatory, however, agrees with Shanks & Pottenger that 1950 was not an
+# exception and that Oct Sun>=1 was maintained through 1965.
+Rule	Port	1947	1966	-	Apr	Sun>=1	 2:00s	1:00	S
 Rule	Port	1947	1965	-	Oct	Sun>=1	 2:00s	0	-
-Rule	Port	1977	only	-	Mar	27	 0:00s	1:00	S
-Rule	Port	1977	only	-	Sep	25	 0:00s	0	-
-Rule	Port	1978	1979	-	Apr	Sun>=1	 0:00s	1:00	S
-Rule	Port	1978	only	-	Oct	 1	 0:00s	0	-
-Rule	Port	1979	1982	-	Sep	lastSun	 1:00s	0	-
-Rule	Port	1980	only	-	Mar	lastSun	 0:00s	1:00	S
-Rule	Port	1981	1982	-	Mar	lastSun	 1:00s	1:00	S
-Rule	Port	1983	only	-	Mar	lastSun	 2:00s	1:00	S
+# From Tim Parenti (2024-03-XXX):
+# Decreto-Lei 47233 of 1966-10-01 considered that the "duality" in time was
+# "the cause of serious disturbances" and noted that "the countries with which
+# we have the most frequent contacts...have already adopted" a solution
+# coinciding with the extant "summer time".  It established that the former
+# "summer time" would apply year-round on the mainland and adjacent islands
+# with immediate effect, as the fall back would have otherwise occurred later
+# that evening.
+# https://dre.pt/dr/detalhe/decreto-lei/47233-1966-293729
+# Model this by changing zones without changing clocks at the
+# previously-appointed fall back time.
+#
+# Decreto-Lei 309/76 of 1976-04-27 acknowledged that those international
+# contacts had returned to adopting seasonal times, and considered that the
+# year-round advancement "entails considerable sacrifices for the vast majority
+# of the working population during the winter months", including morning
+# visibility concerns for schoolchildren.  It specified, beginning 1976-09-26
+# 01:00, an annual return to UT+00 on the mainland from 00:00 UT on Sep lastSun
+# to 00:00 UT on Mar lastSun (unless the latter date fell on Easter, in which
+# case it was to be brought forward to the preceding Sunday).  It also assigned
+# the Permanent Time Commission to study and propose revisions for the Azores
+# and Madeira, neither of which resumed DST until 1982 (as described further
+# below).
+# https://dre.pt/dr/detalhe/decreto-lei/309-1976-502063
+Rule	Port	1977	only	-	Mar	lastSun	 0:00s	1:00	S
+Rule	Port	1977	only	-	Sep	lastSun	 0:00s	0	-
+# From Tim Parenti (2024-03-XXX):
+# Beginning in 1978, rather than triggering the Easter rule of the 1976 decree
+# (Easter fell on 1978-03-26), Article 5 was used instead, which allowed DST
+# dates to be changed by order of the Minister of Education and Scientific
+# Research, upon consultation with the Permanent Time Commission, "whenever
+# considered convenient."  As such, a series of one-off ordinances were
+# promulgated for the mainland in 1978 through 1980, after which the 1976
+# decree naturally came back into force from 1981.
+Rule	Port	1978	1980	-	Apr	Sun>=1	 1:00s	1:00	S
+Rule	Port	1978	only	-	Oct	 1	 1:00s	0	-
+Rule	Port	1979	1980	-	Sep	lastSun	 1:00s	0	-
+Rule	Port	1981	1986	-	Mar	lastSun	 0:00s	1:00	S
+Rule	Port	1981	1985	-	Sep	lastSun	 0:00s	0	-
+# From Tim Parenti (2024-03-XXX):
+# Decreto-Lei 44-B/86 of 1986-03-07 switched mainland Portugal's transition
+# times from 0:00s to 1:00u to harmonize with the EEC from 1986-03-30.
+# https://dre.pt/dr/detalhe/decreto-lei/44-b-1986-628280
+# (Transitions of 1:00s as previously reported and used by the W-Eur rules,
+# though equivalent, appear to have been fiction here.)  Madeira continued to
+# use 0:00s for spring 1986 before joining with the mainland using 1:00u in the
+# fall; meanwhile, in the Azores the two were equivalent, so the law specifying
+# 0:00s wasn't touched until 1992.  (See below for more on the islands.)
+#
+# From Rui Pedro Salgueiro (1992-11-12):
+# Portugal has recently (September, 27) changed timezone
+# (from WET to MET or CET) to harmonize with EEC.
+#
+# Martin Bruckmann (1996-02-29) reports via Peter Ilieve
+# that Portugal is reverting to 0:00 by not moving its clocks this spring.
+# The new Prime Minister was fed up with getting up in the dark in the winter.
+#
+# From Paul Eggert (1996-11-12):
+# IATA SSIM (1991-09) reports several 1991-09 and 1992-09 transitions
+# at 02:00u, not 01:00u.  Assume that these are typos.
 #
 # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
 		#STDOFF	-0:36:44.68
 Zone	Europe/Lisbon	-0:36:45 -	LMT	1884
 			-0:36:45 -	LMT	1912 Jan  1  0:00u # Lisbon MT
-			 0:00	Port	WE%sT	1966 Apr  3  2:00
+			 0:00	Port	WE%sT	1966 Oct  2  2:00s
 			 1:00	-	CET	1976 Sep 26  1:00
-			 0:00	Port	WE%sT	1983 Sep 25  1:00s
-			 0:00	W-Eur	WE%sT	1992 Sep 27  1:00s
+			 0:00	Port	WE%sT	1986
+			 0:00	EU	WE%sT	1992 Sep 27  1:00u
 			 1:00	EU	CE%sT	1996 Mar 31  1:00u
 			 0:00	EU	WE%sT
+
+# From Tim Parenti (2024-03-XXX):
+# For the Azores and Madeira, legislation was followed from the laws currently
+# in force as listed at:
+# https://oal.ul.pt/hora-legal/legislacao/
+# working backward through references of revocation and abrogation to
+# Decreto-Lei 47233 of 1966-10-01, the last time DST was abolished across the
+# mainland and its adjacent islands.  Because of that reference, it is
+# therefore assumed that DST rules in the islands prior to 1966 were like that
+# of the mainland, though most legislation of the time didn't explicitly
+# specify DST practices for the islands.
+#
+# This Zone can be simplified once we assume zic %z.
 Zone Atlantic/Azores	-1:42:40 -	LMT	1884        # Ponta Delgada
 			-1:54:32 -	HMT	1912 Jan  1  2:00u # Horta MT
+# From Tim Parenti (2024-03-XXX):
+# While Decreto-Lei 309/76 of 1976-04-27 reintroduced DST on the mainland by
+# falling back on 1976-09-26, it assigned the Permanent Time Commission to
+# study and propose revisions for the Azores and Madeira.  Decreto Regional
+# 9/77/A of 1977-05-17 affirmed that "the legal time remained unchanged in the
+# Azores" at UT-1, and would remain there year-round.
+# https://dre.pt/dr/detalhe/decreto-regional/9-1977-252066
+#
+# Decreto Regional 2/82/A, published 1982-03-02, adopted DST in the same
+# fashion as the mainland used at the time.
+# https://dre.pt/dr/detalhe/decreto-regional/2-1982-599965
+# Though transitions in the Azores officially remained at 0:00s through 1992,
+# this was equivalent to the EU-style 1:00u adopted by the mainland in 1986, so
+# model it as such.
 # Vanguard section, for zic and other parsers that support %z.
-			-2:00	Port	%z	1966 Apr  3  2:00
-			-1:00	Port	%z	1983 Sep 25  1:00s
-			-1:00	W-Eur	%z	1992 Sep 27  1:00s
+			-2:00	Port	%z	1966 Oct  2  2:00s
+			-1:00	-	%z	1982 Mar 28  0:00s
+			-1:00	Port	%z	1986
 # Rearguard section, for parsers lacking %z; see ziguard.awk.
 #			-2:00	Port	-02/-01	1942 Apr 25 22:00s
 #			-2:00	Port	+00	1942 Aug 15 22:00s
@@ -2177,16 +2340,34 @@ Zone Atlantic/Azores	-1:42:40 -	LMT	1884        # Ponta Delgada
 #			-2:00	Port	+00	1944 Aug 26 22:00s
 #			-2:00	Port	-02/-01	1945 Apr 21 22:00s
 #			-2:00	Port	+00	1945 Aug 25 22:00s
-#			-2:00	Port	-02/-01	1966 Apr  3  2:00
-#			-1:00	Port	-01/+00	1983 Sep 25  1:00s
-#			-1:00	W-Eur	-01/+00	1992 Sep 27  1:00s
+#			-2:00	Port	-02/-01	1966 Oct  2  2:00s
+#			-1:00	-	-01	1982 Mar 28  0:00s
+#			-1:00	Port	-01/+00	1986
 # End of rearguard section.
-			 0:00	EU	WE%sT	1993 Mar 28  1:00u
+			-1:00	EU	%z	1992 Dec 27  1:00s
+# From Paul Eggert (1996-11-12):
+# IATA SSIM (1991/1992) reports that the Azores were at -1:00.
+# IATA SSIM (1993-02) says +0:00; later issues (through 1996-09) say -1:00.
+#
+# From Tim Parenti (2024-03-XXX):
+# After mainland Portugal had shifted forward an hour from 1992-09-27, Decreto
+# Legislativo Regional 29/92/A of 1992-12-23 sought to "reduce the time
+# difference" by shifting the Azores forward as well from 1992-12-27.  Just six
+# months later, this was revoked by Decreto Legislativo Regional 9/93/A, citing
+# "major changes in work habits and way of life."  Though the revocation didn't
+# give a transition time, it was signed Wednesday 1993-06-16; assume it took
+# effect later that evening, and that an EU-style spring forward (to +01) was
+# still observed in the interim on 1993-03-28.
+# https://dre.pt/dr/detalhe/decreto-legislativo-regional/29-1992-621553
+# https://dre.pt/dr/detalhe/decreto-legislativo-regional/9-1993-389633
+			 0:00	EU	WE%sT	1993 Jun 17  1:00u
 			-1:00	EU	%z
+
+# This Zone can be simplified once we assume zic %z.
 Zone Atlantic/Madeira	-1:07:36 -	LMT	1884        # Funchal
 			-1:07:36 -	FMT	1912 Jan  1  1:00u # Funchal MT
 # Vanguard section, for zic and other parsers that support %z.
-			-1:00	Port	%z	1966 Apr  3  2:00
+			-1:00	Port	%z	1966 Oct  2  2:00s
 # Rearguard section, for parsers lacking %z; see ziguard.awk.
 #			-1:00	Port	-01/+00	1942 Apr 25 22:00s
 #			-1:00	Port	+01	1942 Aug 15 22:00s
@@ -2196,9 +2377,22 @@ Zone Atlantic/Madeira	-1:07:36 -	LMT	1884        # Funchal
 #			-1:00	Port	+01	1944 Aug 26 22:00s
 #			-1:00	Port	-01/+00	1945 Apr 21 22:00s
 #			-1:00	Port	+01	1945 Aug 25 22:00s
-#			-1:00	Port	-01/+00	1966 Apr  3  2:00
+#			-1:00	Port	-01/+00	1966 Oct  2  2:00s
 # End of rearguard section.
-			 0:00	Port	WE%sT	1983 Sep 25  1:00s
+# From Tim Parenti (2024-03-XXX):
+# Decreto Regional 5/82/M, published 1982-04-03, established DST transitions at
+# 0:00u, which for Madeira is equivalent to the mainland's rules (0:00s) at the
+# time.  It came into effect the day following its publication, Sunday
+# 1982-04-04, thus resuming Madeira's DST practice about a week later than the
+# mainland and the Azores.
+# https://dre.pt/dr/detalhe/decreto-regional/5-1982-608273
+#
+# Decreto Legislativo Regional 18/86/M, published 1986-10-01, adopted EU-style
+# rules (1:00u) and entered into immediate force after being signed on
+# 1986-07-31.
+# https://dre.pt/dr/detalhe/decreto-legislativo-regional/18-1986-221705
+			 0:00	-	WET	1982 Apr  4
+			 0:00	Port	WE%sT	1986 Jul 31
 			 0:00	EU	WE%sT
 
 # Romania
-- 
2.40.1

