Support timezone abbreviations that sometimes change.

Up to now, PG has assumed that any given timezone abbreviation (such as
"EDT") represents a constant GMT offset in the usage of any particular
region; we had a way to configure what that offset was, but not for it
to be changeable over time.  But, as with most things horological, this
view of the world is too simplistic: there are numerous regions that have
at one time or another switched to a different GMT offset but kept using
the same timezone abbreviation.  Almost the entire Russian Federation did
that a few years ago, and later this month they're going to do it again.
And there are similar examples all over the world.

To cope with this, invent the notion of a "dynamic timezone abbreviation",
which is one that is referenced to a particular underlying timezone
(as defined in the IANA timezone database) and means whatever it currently
means in that zone.  For zones that use or have used daylight-savings time,
the standard and DST abbreviations continue to have the property that you
can specify standard or DST time and get that time offset whether or not
DST was theoretically in effect at the time.  However, the abbreviations
mean what they meant at the time in question (or most recently before that
time) rather than being absolutely fixed.

The standard abbreviation-list files have been changed to use this behavior
for abbreviations that have actually varied in meaning since 1970.  The
old simple-numeric definitions are kept for abbreviations that have not
changed, since they are a bit faster to resolve.

While this is clearly a new feature, it seems necessary to back-patch it
into all active branches, because otherwise use of Russian zone
abbreviations is going to become even more problematic than it already was.
This change supersedes the changes in commit 513d06ded et al to modify the
fixed meanings of the Russian abbreviations; since we've not shipped that
yet, this will avoid an undesirably incompatible (not to mention incorrect)
change in behavior for timestamps between 2011 and 2014.

This patch makes some cosmetic changes in ecpglib to keep its usage of
datetime lookup tables as similar as possible to the backend code, but
doesn't do anything about the increasingly obsolete set of timezone
abbreviation definitions that are hard-wired into ecpglib.  Whatever we
do about that will likely not be appropriate material for back-patching.
Also, a potential free() of a garbage pointer after an out-of-memory
failure in ecpglib has been fixed.

This patch also fixes pre-existing bugs in DetermineTimeZoneOffset() that
caused it to produce unexpected results near a timezone transition, if
both the "before" and "after" states are marked as standard time.  We'd
only ever thought about or tested transitions between standard and DST
time, but that's not what's happening when a zone simply redefines their
base GMT offset.

In passing, update the SGML documentation to refer to the Olson/zoneinfo/
zic timezone database as the "IANA" database, since it's now being
maintained under the auspices of IANA.

1 files changed, 52 insertions, 53 deletions

diff --git a/src/timezone/tznames/Default b/src/timezone/tznames/Default
index 9e5209e779b..a8b8eac5182 100644
--- a/src/timezone/tznames/Default
+++ b/src/timezone/tznames/Default
@@ -54,7 +54,7 @@ AKST   -32400    # Alaska Standard Time
                  #     (America/Juneau)
                  #     (America/Nome)
                  #     (America/Yakutat)
-ART    -10800    # Argentina Time
+ART    America/Argentina/Buenos_Aires  # Argentina Time
                  #     (America/Argentina/Buenos_Aires)
                  #     (America/Argentina/Cordoba)
                  #     (America/Argentina/Tucuman)
@@ -65,7 +65,7 @@ ART    -10800    # Argentina Time
                  #     (America/Argentina/Mendoza)
                  #     (America/Argentina/Rio_Gallegos)
                  #     (America/Argentina/Ushuaia)
-ARST    -7200 D  # Argentina Summer Time
+ARST    America/Argentina/Buenos_Aires  # Argentina Summer Time
 BOT    -14400    # Bolivia Time
                  #     (America/La_Paz)
 BRA    -10800    # Brazil Time (not in zic)
@@ -170,7 +170,7 @@ FNST    -3600 D  # Fernando de Noronha Summer Time (not in zic)
                  #     (America/Noronha)
 GFT    -10800    # French Guiana Time
                  #     (America/Cayenne)
-GYT    -14400    # Guyana Time
+GYT    America/Guyana  # Guyana Time
                  #     (America/Guyana)
 MDT    -21600 D  # Mexico Mountain Daylight Time
                  # Mountain Daylight Time
@@ -219,13 +219,13 @@ PST    -28800    # Pacific Standard Time
                  #     (Pacific/Pitcairn)
 PYST   -10800 D  # Paraguay Summer Time
                  #     (America/Asuncion)
-PYT    -14400    # Paraguay Time
+PYT    America/Asuncion  # Paraguay Time
                  #     (America/Asuncion)
 UYST    -7200 D  # Uruguay Summer Time
                  #     (America/Montevideo)
 UYT    -10800    # Uruguay Time
                  #     (America/Montevideo)
-VET    -16200    # Venezuela Time (caution: this used to mean -14400)
+VET    America/Caracas  # Venezuela Time
                  #     (America/Caracas)
 WGST    -7200 D  # Western Greenland Summer Time
                  #     (America/Godthab)
@@ -234,13 +234,13 @@ WGT    -10800    # West Greenland Time
 
 #################### ANTARCTICA ####################
 
-DAVT    25200    # Davis Time (Antarctica)
+DAVT    Antarctica/Davis  # Davis Time (Antarctica)
                  #     (Antarctica/Davis)
 DDUT    36000    # Dumont-d'Urville Time (Antarctica)
                  #     (Antarctica/DumontDUrville)
                  #     (Antarctica/Palmer)
                  #     (America/Santiago)
-MAWT    18000    # Mawson Time (Antarctica) (caution: this used to mean 21600)
+MAWT    Antarctica/Mawson  # Mawson Time (Antarctica)
                  #     (Antarctica/Mawson)
 
 #################### ASIA ####################
@@ -253,19 +253,19 @@ ALMST   25200 D  # Alma-Ata Summer Time (obsolete)
 # CONFLICT! AMST is not unique
 # Other timezones:
 #  - AMST: Amazon Summer Time (America)
-AMST    18000 D  # Armenia Summer Time
+AMST    Asia/Yerevan  # Armenia Summer Time
                  #     (Asia/Yerevan)
 # CONFLICT! AMT is not unique
 # Other timezones:
 #  - AMT: Amazon Time (America)
-AMT     14400    # Armenia Time
+AMT     Asia/Yerevan  # Armenia Time
                  #     (Asia/Yerevan)
-ANAST   46800 D  # Anadyr Summer Time (obsolete)
-ANAT    43200    # Anadyr Time
+ANAST   Asia/Anadyr  # Anadyr Summer Time (obsolete)
+ANAT    Asia/Anadyr  # Anadyr Time
                  #     (Asia/Anadyr)
-AZST    18000 D  # Azerbaijan Summer Time
+AZST    Asia/Baku  # Azerbaijan Summer Time
                  #     (Asia/Baku)
-AZT     14400    # Azerbaijan Time
+AZT     Asia/Baku  # Azerbaijan Time
                  #     (Asia/Baku)
 BDT     21600    # Bangladesh Time
                  #     (Asia/Dhaka)
@@ -275,9 +275,8 @@ BORT    28800    # Borneo Time (Indonesia) (not in zic)
 BTT     21600    # Bhutan Time
                  #     (Asia/Thimphu)
 CCT     28800    # China Coastal Time (not in zic)
-GEST    14400 D  # Georgia Summer Time (obsolete)
-                 #     (Asia/Tbilisi)
-GET     14400    # Georgia Time (caution: this used to mean 10800)
+GEST    Asia/Tbilisi  # Georgia Summer Time (obsolete)
+GET     Asia/Tbilisi  # Georgia Time
                  #     (Asia/Tbilisi)
 HKT     28800    # Hong Kong Time (not in zic)
 ICT     25200    # Indochina Time
@@ -287,8 +286,8 @@ ICT     25200    # Indochina Time
                  #     (Asia/Vientiane)
 IDT     10800 D  # Israel Daylight Time
                  #     (Asia/Jerusalem)
-IRKST   32400 D  # Irkutsk Summer Time (obsolete)
-IRKT    28800    # Irkutsk Time (caution: this used to mean 32400)
+IRKST   Asia/Irkutsk  # Irkutsk Summer Time (obsolete)
+IRKT    Asia/Irkutsk  # Irkutsk Time
                  #     (Asia/Irkutsk)
 IRT     12600    # Iran Time (not in zic)
 # CONFLICT! IST is not unique
@@ -302,33 +301,32 @@ JST     32400    # Japan Standard Time
                  #     (Asia/Tokyo)
 KDT     36000 D  # Korean Daylight Time (not in zic)
 KGST    21600 D  # Kyrgyzstan Summer Time (obsolete)
+KGT     Asia/Bishkek  # Kyrgyzstan Time
                  #     (Asia/Bishkek)
-KGT     21600    # Kyrgyzstan Time (caution: this used to mean 18000)
-                 #     (Asia/Bishkek)
-KRAST   28800 D  # Krasnoyarsk Summer Time (obsolete)
-KRAT    25200    # Krasnoyarsk Time (caution: this used to mean 28800)
+KRAST   Asia/Krasnoyarsk  # Krasnoyarsk Summer Time (obsolete)
+KRAT    Asia/Krasnoyarsk  # Krasnoyarsk Time
                  #     (Asia/Krasnoyarsk)
 KST     32400    # Korean Standard Time
                  #     (Asia/Pyongyang)
-LKT     21600    # Lanka Time (obsolete)
-MAGST   43200 D  # Magadan Summer Time (obsolete)
-MAGT    36000    # Magadan Time (caution: this used to mean 43200)
+LKT     Asia/Colombo  # Lanka Time (obsolete)
+MAGST   Asia/Magadan  # Magadan Summer Time (obsolete)
+MAGT    Asia/Magadan  # Magadan Time
                  #     (Asia/Magadan)
 MMT     23400    # Myanmar Time
                  #     (Asia/Rangoon)
 MYT     28800    # Malaysia Time
                  #     (Asia/Kuala_Lumpur)
                  #     (Asia/Kuching)
-NOVST   25200 D  # Novosibirsk Summer Time (obsolete)
-NOVT    21600    # Novosibirsk Time (caution: this used to mean 25200)
+NOVST   Asia/Novosibirsk  # Novosibirsk Summer Time (obsolete)
+NOVT    Asia/Novosibirsk  # Novosibirsk Time
                  #     (Asia/Novosibirsk)
 NPT     20700    # Nepal Time
                  #     (Asia/Katmandu)
-OMSST   25200 D  # Omsk Summer Time (obsolete)
-OMST    21600    # Omsk Time (caution: this used to mean 25200)
+OMSST   Asia/Omsk  # Omsk Summer Time (obsolete)
+OMST    Asia/Omsk  # Omsk Time
                  #     (Asia/Omsk)
-PETST   46800 D  # Petropavlovsk-Kamchatski Summer Time (obsolete)
-PETT    43200    # Petropavlovsk-Kamchatski Time
+PETST   Asia/Kamchatka  # Petropavlovsk-Kamchatski Summer Time (obsolete)
+PETT    Asia/Kamchatka  # Petropavlovsk-Kamchatski Time
                  #     (Asia/Kamchatka)
 PHT     28800    # Philippine Time
                  #     (Asia/Manila)
@@ -336,14 +334,14 @@ PKT     18000    # Pakistan Time
                  #     (Asia/Karachi)
 PKST    21600 D  # Pakistan Summer Time
                  #     (Asia/Karachi)
-SGT     28800    # Singapore Time
+SGT     Asia/Singapore  # Singapore Time
                  #     (Asia/Singapore)
 TJT     18000    # Tajikistan Time
                  #     (Asia/Dushanbe)
-TMT     18000    # Turkmenistan Time
+TMT     Asia/Ashgabat  # Turkmenistan Time
                  #     (Asia/Ashgabat)
 ULAST   32400 D  # Ulan Bator Summer Time (obsolete)
-ULAT    28800    # Ulan Bator Time
+ULAT    Asia/Ulaanbaatar  # Ulan Bator Time
                  #     (Asia/Ulaanbaatar)
 UZST    21600 D  # Uzbekistan Summer Time
                  #     (Asia/Samarkand)
@@ -351,16 +349,16 @@ UZST    21600 D  # Uzbekistan Summer Time
 UZT     18000    # Uzbekistan Time
                  #     (Asia/Samarkand)
                  #     (Asia/Tashkent)
-VLAST   39600 D  # Vladivostok Summer Time (obsolete)
-VLAT    36000    # Vladivostok Time (caution: this used to mean 39600)
+VLAST   Asia/Vladivostok  # Vladivostok Summer Time (obsolete)
+VLAT    Asia/Vladivostok  # Vladivostok Time
                  #     (Asia/Vladivostok)
 XJT     21600    # Xinjiang Time
                  #     (Asia/Urumqi)
-YAKST   36000 D  # Yakutsk Summer Time (obsolete)
-YAKT    32400    # Yakutsk Time (caution: this used to mean 36000)
+YAKST   Asia/Yakutsk  # Yakutsk Summer Time (obsolete)
+YAKT    Asia/Yakutsk  # Yakutsk Time
                  #     (Asia/Yakutsk)
 YEKST   21600 D  # Yekaterinburg Summer Time (obsolete)
-YEKT    18000    # Yekaterinburg Time (caution: this used to mean 21600)
+YEKT    Asia/Yekaterinburg  # Yekaterinburg Time
                  #     (Asia/Yekaterinburg)
 
 #################### ATLANTIC ####################
@@ -406,9 +404,9 @@ AZOST       0 D  # Azores Summer Time
                  #     (Atlantic/Azores)
 AZOT    -3600    # Azores Time
                  #     (Atlantic/Azores)
-FKST   -10800    # Falkland Islands Summer Time (now used all year round)
+FKST    Atlantic/Stanley  # Falkland Islands Summer/Standard Time
                  #     (Atlantic/Stanley)
-FKT    -14400    # Falkland Islands Time (obsolete)
+FKT     Atlantic/Stanley  # Falkland Islands Time (obsolete)
 
 #################### AUSTRALIA ####################
 
@@ -443,7 +441,7 @@ AWST    28800    # Australian Western Standard Time
                  #     (Australia/Perth)
 CADT    37800 D  # Central Australia Daylight-Saving Time (not in zic)
 CAST    34200    # Central Australia Standard Time (not in zic)
-LHDT    39600 D  # Lord Howe Daylight Time
+LHDT    Australia/Lord_Howe  # Lord Howe Daylight Time
                  #     (Australia/Lord_Howe)
 LHST    37800    # Lord Howe Standard Time
                  #     (Australia/Lord_Howe)
@@ -639,9 +637,10 @@ MET      3600    # Middle Europe Time (not in zic)
 METDST   7200 D  # Middle Europe Summer Time (not in zic)
 MEZ      3600    # Mitteleuropaeische Zeit (German) (not in zic)
 MSD     14400 D  # Moscow Daylight Time (obsolete)
-MSK     10800    # Moscow Time (caution: this used to mean 14400)
+MSK     Europe/Moscow  # Moscow Time
                  #     (Europe/Moscow)
-VOLT    14400    # Volgograd Time (obsolete)
+                 #     (Europe/Volgograd)
+VOLT    Europe/Volgograd  # Volgograd Time (obsolete)
 WET         0    # Western Europe Time
                  #     (Africa/Casablanca)
                  #     (Africa/El_Aaiun)
@@ -659,7 +658,7 @@ WETDST   3600 D  # Western Europe Summer Time
 
 CXT     25200    # Christmas Island Time (Indian Ocean)
                  #     (Indian/Christmas)
-IOT     21600    # British Indian Ocean Territory (Chagos) (there was a timezone change recently in 1996)
+IOT     Indian/Chagos  # British Indian Ocean Territory (Chagos)
                  #     (Indian/Chagos)
 MUT     14400    # Mauritius Island Time
                  #     (Indian/Mauritius)
@@ -682,11 +681,11 @@ CHAST   45900    # Chatham Standard Time (New Zealand)
                  #     (Pacific/Chatham)
 CHUT    36000    # Chuuk Time
                  #     (Pacific/Chuuk)
-CKT    -36000    # Cook Islands Time (caution: this used to mean 43200)
+CKT     Pacific/Rarotonga  # Cook Islands Time
                  #     (Pacific/Rarotonga)
-EASST  -18000 D  # Easter Island Summer Time (Chile)
+EASST   Pacific/Easter  # Easter Island Summer Time (Chile)
                  #     (Pacific/Easter)
-EAST   -21600    # Easter Island Time (Chile)
+EAST    Pacific/Easter  # Easter Island Time (Chile)
                  #     (Pacific/Easter)
 FJST    46800 D  # Fiji Summer Time
                  #     (Pacific/Fiji)
@@ -701,9 +700,9 @@ GILT    43200    # Gilbert Islands Time
 HST    -36000    # Hawaiian Standard Time
                  #     (Pacific/Honolulu)
                  #     (Pacific/Johnston)
-KOST    39600    # Kosrae Time
+KOST    Pacific/Kosrae  # Kosrae Time
                  #     (Pacific/Kosrae)
-LINT    50400    # Line Islands Time (Kiribati)
+LINT    Pacific/Kiritimati  # Line Islands Time (Kiribati)
                  #     (Pacific/Kiritimati)
 MART   -34200    # Marquesas Time
                  #     (Pacific/Marquesas)
@@ -715,7 +714,7 @@ MPT     36000    # North Mariana Islands Time (not in zic)
 # Other timezones:
 #  - NFT: Norfolk Time (Pacific)
 NFT    -12600    # Newfoundland Time (not in zic)
-NUT    -39600    # Niue Time
+NUT     Pacific/Niue  # Niue Time
                  #     (Pacific/Niue)
 NZDT    46800 D  # New Zealand Daylight Time
                  #     (Antarctica/McMurdo)
@@ -725,7 +724,7 @@ NZST    43200    # New Zealand Standard Time
                  #     (Pacific/Auckland)
 PGT     36000    # Papua New Guinea Time
                  #     (Pacific/Port_Moresby)
-PHOT    46800    # Phoenix Islands Time (Kiribati)
+PHOT    Pacific/Enderbury  # Phoenix Islands Time (Kiribati)
                  #     (Pacific/Enderbury)
 PONT    39600    # Ponape Time (Micronesia)
                  #     (Pacific/Ponape)
@@ -733,7 +732,7 @@ PWT     32400    # Palau Time
                  #     (Pacific/Palau)
 TAHT   -36000    # Tahiti Time (zic says "TAHT", other sources "THAT")
                  #     (Pacific/Tahiti)
-TKT     46800    # Tokelau Time (caution: this used to mean -36000)
+TKT     Pacific/Fakaofo  # Tokelau Time
                  #     (Pacific/Fakaofo)
 TOT     46800    # Tonga Time
                  #     (Pacific/Tongatapu)