Reorder 'backward’

* Makefile (check_sorted): Adjust to match new 'backward'.
* backward: Divide into sections, explaining better the reason for
each link in 'backward'.  This does not change the generated data.

Makefile

@@ -820,7 +820,8 @@ check_slashed_abbrs: $(TDATA_TO_CHECK)
 CHECK_CC_LIST = { n = split($$1,a,/,/); for (i=2; i<=n; i++) print a[1], a[i]; }
 
 check_sorted: backward backzone iso3166.tab zone.tab zone1970.tab
-		$(AWK) '/^Link/ {print $$3}' backward | LC_ALL=C sort -cu
+		$(AWK) '/^Link/ {printf "%.5d %s\n", g, $$3} /^$$/ {g++}' \
+		  backward | LC_ALL=C sort -cu
 		$(AWK) '/^Zone/ {print $$2}' backzone | LC_ALL=C sort -cu
 		touch $@
 

backward

@@ -4,7 +4,7 @@
 # 2009-05-17 by Arthur David Olson.
 
 # This file provides links from old or merged timezone names to current ones.
-# Many names changed in late 1993, and many merged names moved here
+# Many names changed in 1993 and in 1995, and many merged names moved here
 # in the period from 2013 through 2022.  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.
@@ -13,6 +13,12 @@
 # building with 'make BACKWARD=', in practice downstream users
 # typically use this file for backward compatibility.
 
+# This file is divided into sections, one for each major reason for a
+# backward compatibility link.  Each section is sorted by link name.
+
+
+# Pre-1993 naming conventions
+
 # Link	TARGET			LINK-NAME
 Link	Africa/Abidjan		Africa/Accra
 Link	Africa/Nairobi		Africa/Addis_Ababa
@@ -80,10 +86,8 @@ Link	America/Argentina/Mendoza	America/Mendoza
 Link	America/Toronto		America/Montreal
 Link	America/Puerto_Rico	America/Montserrat
 Link	America/Toronto		America/Nassau
-Link	America/Toronto		America/Nipigon
 Link	America/Puerto_Rico	America/Port_of_Spain
 Link	America/Rio_Branco	America/Porto_Acre
-Link	America/Winnipeg	America/Rainy_River
 Link	America/Argentina/Cordoba	America/Rosario
 Link	America/Tijuana		America/Santa_Isabel
 Link	America/Denver		America/Shiprock
@@ -92,7 +96,6 @@ 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/Toronto		America/Thunder_Bay
 Link	America/Puerto_Rico	America/Tortola
 Link	America/Puerto_Rico	America/Virgin
 Link	Pacific/Port_Moresby	Antarctica/DumontDUrville
@@ -131,8 +134,6 @@ Link	Europe/Berlin		Atlantic/Jan_Mayen
 Link	Africa/Abidjan		Atlantic/Reykjavik
 Link	Africa/Abidjan		Atlantic/St_Helena
 Link	Australia/Sydney	Australia/ACT
-Link	Australia/Sydney	Australia/Canberra
-Link	Australia/Hobart	Australia/Currie
 Link	Australia/Lord_Howe	Australia/LHI
 Link	Australia/Sydney	Australia/NSW
 Link	Australia/Darwin	Australia/North
@@ -177,34 +178,6 @@ Link	Etc/GMT			Etc/Greenwich
 Link	Etc/UTC			Etc/UCT
 Link	Etc/UTC			Etc/Universal
 Link	Etc/UTC			Etc/Zulu
-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/Kyiv		Europe/Kiev
-Link	Europe/Belgrade		Europe/Ljubljana
-Link	Europe/Brussels		Europe/Luxembourg
-Link	Europe/Helsinki		Europe/Mariehamn
-Link	Europe/Paris		Europe/Monaco
-# Classically, Cyprus is in Asia; e.g. see Herodotus, Histories, I.72.
-# However, for various reasons many users expect to find it under Europe.
-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/Kyiv		Europe/Uzhgorod
-Link	Europe/Zurich		Europe/Vaduz
-Link	Europe/Rome		Europe/Vatican
-Link	Europe/Belgrade		Europe/Zagreb
-Link	Europe/Kyiv		Europe/Zaporozhye
 Link	Europe/London		GB
 Link	Europe/London		GB-Eire
 # Vanguard section, for most .zi parsers.
@@ -220,14 +193,6 @@ Link	Etc/GMT			Greenwich
 # End of rearguard section.
 Link	Asia/Hong_Kong		Hongkong
 Link	Africa/Abidjan		Iceland
-Link	Africa/Nairobi		Indian/Antananarivo
-Link	Asia/Bangkok		Indian/Christmas
-Link	Asia/Yangon		Indian/Cocos
-Link	Africa/Nairobi		Indian/Comoro
-Link	Indian/Maldives		Indian/Kerguelen
-Link	Asia/Dubai		Indian/Mahe
-Link	Africa/Nairobi		Indian/Mayotte
-Link	Asia/Dubai		Indian/Reunion
 Link	Asia/Tehran		Iran
 Link	Asia/Jerusalem		Israel
 Link	America/Jamaica		Jamaica
@@ -241,20 +206,6 @@ Link	Pacific/Auckland	NZ
 Link	Pacific/Chatham		NZ-CHAT
 Link	America/Denver		Navajo
 Link	Asia/Shanghai		PRC
-Link	Pacific/Port_Moresby	Pacific/Chuuk
-Link	Pacific/Kanton		Pacific/Enderbury
-Link	Pacific/Tarawa		Pacific/Funafuti
-Link	Pacific/Honolulu	Pacific/Johnston
-Link	Pacific/Tarawa		Pacific/Majuro
-Link	Pacific/Pago_Pago	Pacific/Midway
-Link	Pacific/Guadalcanal	Pacific/Pohnpei
-Link	Pacific/Guadalcanal	Pacific/Ponape
-Link	Pacific/Guam		Pacific/Saipan
-Link	Pacific/Pago_Pago	Pacific/Samoa
-Link	Pacific/Port_Moresby	Pacific/Truk
-Link	Pacific/Tarawa		Pacific/Wake
-Link	Pacific/Tarawa		Pacific/Wallis
-Link	Pacific/Port_Moresby	Pacific/Yap
 Link	Europe/Warsaw		Poland
 Link	Europe/Lisbon		Portugal
 Link	Asia/Taipei		ROC
@@ -278,3 +229,192 @@ Link	Etc/UTC			UTC
 Link	Etc/UTC			Universal
 Link	Europe/Moscow		W-SU
 Link	Etc/UTC			Zulu
+
+
+# Two-part names that were renamed mostly to three-part names in 1995
+
+# Link	TARGET				LINK-NAME
+Link	America/Argentina/Buenos_Aires	America/Buenos_Aires
+Link	America/Argentina/Catamarca	America/Catamarca
+Link	America/Argentina/Cordoba	America/Cordoba
+Link	America/Indiana/Indianapolis	America/Indianapolis
+Link	America/Argentina/Jujuy		America/Jujuy
+Link	America/Indiana/Knox		America/Knox_IN
+Link	America/Kentucky/Louisville	America/Louisville
+Link	America/Argentina/Mendoza	America/Mendoza
+Link	America/Puerto_Rico		America/Virgin
+Link	Pacific/Pago_Pago		Pacific/Samoa
+
+
+# Pre-2013 practice, which typically had a Zone per zone.tab line
+
+# Link	TARGET			LINK-NAME
+Link	Africa/Abidjan		Africa/Accra
+Link	Africa/Nairobi		Africa/Addis_Ababa
+Link	Africa/Nairobi		Africa/Asmara
+Link	Africa/Abidjan		Africa/Bamako
+Link	Africa/Lagos		Africa/Bangui
+Link	Africa/Abidjan		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	Africa/Nairobi		Africa/Dar_es_Salaam
+Link	Africa/Nairobi		Africa/Djibouti
+Link	Africa/Lagos		Africa/Douala
+Link	Africa/Abidjan		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	Africa/Lagos		Africa/Luanda
+Link	Africa/Maputo		Africa/Lubumbashi
+Link	Africa/Maputo		Africa/Lusaka
+Link	Africa/Lagos		Africa/Malabo
+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	Africa/Lagos		Africa/Porto-Novo
+Link	America/Puerto_Rico	America/Anguilla
+Link	America/Puerto_Rico	America/Antigua
+Link	America/Puerto_Rico	America/Aruba
+Link	America/Panama		America/Atikokan
+Link	America/Puerto_Rico	America/Blanc-Sablon
+Link	America/Panama		America/Cayman
+Link	America/Phoenix		America/Creston
+Link	America/Puerto_Rico	America/Curacao
+Link	America/Puerto_Rico	America/Dominica
+Link	America/Puerto_Rico	America/Grenada
+Link	America/Puerto_Rico	America/Guadeloupe
+Link	America/Puerto_Rico	America/Kralendijk
+Link	America/Puerto_Rico	America/Lower_Princes
+Link	America/Puerto_Rico	America/Marigot
+Link	America/Puerto_Rico	America/Montserrat
+Link	America/Toronto		America/Nassau
+Link	America/Puerto_Rico	America/Port_of_Spain
+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	Pacific/Port_Moresby	Antarctica/DumontDUrville
+Link	Pacific/Auckland	Antarctica/McMurdo
+Link	Asia/Riyadh		Antarctica/Syowa
+Link	Asia/Urumqi		Antarctica/Vostok
+Link	Europe/Berlin		Arctic/Longyearbyen
+Link	Asia/Riyadh		Asia/Aden
+Link	Asia/Qatar		Asia/Bahrain
+Link	Asia/Kuching		Asia/Brunei
+Link	Asia/Singapore		Asia/Kuala_Lumpur
+Link	Asia/Riyadh		Asia/Kuwait
+Link	Asia/Dubai		Asia/Muscat
+Link	Asia/Bangkok		Asia/Phnom_Penh
+Link	Asia/Bangkok		Asia/Vientiane
+Link	Africa/Abidjan		Atlantic/Reykjavik
+Link	Africa/Abidjan		Atlantic/St_Helena
+Link	Europe/Brussels		Europe/Amsterdam
+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	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/Zurich		Europe/Vaduz
+Link	Europe/Rome		Europe/Vatican
+Link	Europe/Belgrade		Europe/Zagreb
+Link	Africa/Nairobi		Indian/Antananarivo
+Link	Asia/Bangkok		Indian/Christmas
+Link	Asia/Yangon		Indian/Cocos
+Link	Africa/Nairobi		Indian/Comoro
+Link	Indian/Maldives		Indian/Kerguelen
+Link	Asia/Dubai		Indian/Mahe
+Link	Africa/Nairobi		Indian/Mayotte
+Link	Asia/Dubai		Indian/Reunion
+Link	Pacific/Port_Moresby	Pacific/Chuuk
+Link	Pacific/Tarawa		Pacific/Funafuti
+Link	Pacific/Tarawa		Pacific/Majuro
+Link	Pacific/Pago_Pago	Pacific/Midway
+Link	Pacific/Guadalcanal	Pacific/Pohnpei
+Link	Pacific/Guam		Pacific/Saipan
+Link	Pacific/Tarawa		Pacific/Wake
+Link	Pacific/Tarawa		Pacific/Wallis
+
+
+# Non-zone.tab locations with timestamps since 1970 that duplicate
+# those of an existing location
+
+# Link	TARGET			LINK-NAME
+Link	Africa/Abidjan		Africa/Timbuktu
+Link	America/Argentina/Catamarca	America/Argentina/ComodRivadavia
+Link	America/Adak		America/Atka
+Link	America/Panama		America/Coral_Harbour
+Link	America/Tijuana		America/Ensenada
+Link	America/Indiana/Indianapolis	America/Fort_Wayne
+Link	America/Toronto		America/Montreal
+Link	America/Toronto		America/Nipigon
+Link	America/Rio_Branco	America/Porto_Acre
+Link	America/Winnipeg	America/Rainy_River
+Link	America/Argentina/Cordoba	America/Rosario
+Link	America/Tijuana		America/Santa_Isabel
+Link	America/Denver		America/Shiprock
+Link	America/Toronto		America/Thunder_Bay
+Link	Pacific/Auckland	Antarctica/South_Pole
+Link	Asia/Shanghai		Asia/Chongqing
+Link	Asia/Shanghai		Asia/Harbin
+Link	Asia/Urumqi		Asia/Kashgar
+Link	Asia/Jerusalem		Asia/Tel_Aviv
+Link	Europe/Berlin		Atlantic/Jan_Mayen
+Link	Australia/Sydney	Australia/Canberra
+Link	Australia/Hobart	Australia/Currie
+Link	Europe/London		Europe/Belfast
+Link	Europe/Chisinau		Europe/Tiraspol
+Link	Europe/Kyiv		Europe/Uzhgorod
+Link	Europe/Kyiv		Europe/Zaporozhye
+Link	Pacific/Kanton		Pacific/Enderbury
+Link	Pacific/Honolulu	Pacific/Johnston
+Link	Pacific/Port_Moresby	Pacific/Yap
+
+
+# Alternate names for the same location
+
+# Link	TARGET			LINK-NAME
+Link	Africa/Nairobi		Africa/Asmera
+Link	America/Nuuk		America/Godthab
+Link	Asia/Ashgabat		Asia/Ashkhabad
+Link	Asia/Kolkata		Asia/Calcutta
+Link	Asia/Shanghai		Asia/Chungking
+Link	Asia/Dhaka		Asia/Dacca
+# Istanbul is in both continents.
+Link	Europe/Istanbul		Asia/Istanbul
+Link	Asia/Kathmandu		Asia/Katmandu
+Link	Asia/Macau		Asia/Macao
+Link	Asia/Yangon		Asia/Rangoon
+Link	Asia/Ho_Chi_Minh	Asia/Saigon
+Link	Asia/Thimphu		Asia/Thimbu
+Link	Asia/Makassar		Asia/Ujung_Pandang
+Link	Asia/Ulaanbaatar	Asia/Ulan_Bator
+Link	Atlantic/Faroe		Atlantic/Faeroe
+Link	Europe/Kyiv		Europe/Kiev
+# Classically, Cyprus is in Asia; e.g. see Herodotus, Histories, I.72.
+# However, for various reasons many users expect to find it under Europe.
+Link	Asia/Nicosia		Europe/Nicosia
+Link	Pacific/Guadalcanal	Pacific/Ponape
+Link	Pacific/Port_Moresby	Pacific/Truk