2021.2.post0: Release of upstream tzdata 2021b

Version 2021.2.post0

Upstream version 2021b released 2021-09-24T23:23:00+00:00

Briefly:

Jordan now starts DST on February's last Thursday. Samoa no longer observes DST.
Merge more location-based Zones whose timestamps agree since 1970. Move some
backward-compatibility links to 'backward'. Rename Pacific/Enderbury to
Pacific/Kanton. Correct many pre-1993 transitions in Malawi, Portugal, etc. zic
now creates each output file or link atomically.

This release is prompted by recent announcements by Jordan and Samoa. It
incorporates many other changes that had accumulated since 2021a. However, it
omits most proposed changes that merged all Zones agreeing since 1970, as
concerns were raised about doing too many of these changes at once. It does
keeps some of these changes in the interest of making tzdb more equitable one
step at a time; see "Merge more location-based Zones" below.

Changes to future timestamps

Jordan now starts DST on February's last Thursday. (Thanks to Steffen Thorsen.)

Samoa no longer observes DST. (Thanks to Geoffrey D. Bennett.)

Changes to zone name

Rename Pacific/Enderbury to Pacific/Kanton. When we added Enderbury in 1993, we
did not know that it is uninhabited and that Kanton (population two dozen) is
the only inhabited location in that timezone. The old name is now a backward-
compatility link.

Changes to past timestamps

Correct many pre-1993 transitions, fixing entries originally derived from
Shanks, Whitman, and Mundell. The fixes include:

• Barbados: standard time was introduced in 1911, not 1932; and DST was
  observed in 1942-1944
• Cook Islands: In 1899 they switched from east to west of GMT, celebrating
  Christmas for two days. They (and Niue) switched to standard time in 1952,
  not 1901.
• Guyana: corrected LMT for Georgetown; the introduction of standard time in
  1911, not 1915; and corrections to 1975 and 1992 transitions
• Kanton: uninhabited before 1937-08-31
• Niue: only observed -11:20 from 1952 through 1964, then went to -11 instead
  of -11:30
• Portugal: DST was observed in 1950
• Tonga: corrected LMT; the introduction of standard time in 1945, not 1901;
  and corrections to the transition from +12:20 to +13 in 1961, not 1941

Additional fixes to entries in the 'backzone' file include:

• Enderbury: inhabited only 1860/1885 and 1938-03-06/1942-02-09
• The Gambia: 1933 and 1942 transitions
• Malawi: several 1911 through 1925 transitions
• Sierra Leone: several 1913 through 1941 transitions, and DST was NOT observed
  in 1957 through 1962 (Thanks to P Chan, Michael Deckers, Alexander
  Krivenyshev and Alois Treindl.)

Merge more location-based Zones whose timestamps agree since 1970, as pre-1970
timestamps are out of scope. This is part of a process that has been ongoing
since 2013. This 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 link in 'backward'. For
example, move America/Creston data to 'backzone' with a link in 'backward' from
America/Phoenix because the two timezones' timestamps agree since 1970; this
change affects some pre-1968 timestamps in America/Creston because Creston and
Phoenix disagreed before 1968. The affected Zones are Africa/Accra,
America/Atikokan, America/Blanc-Sablon, America/Creston, America/Curacao,
America/Nassau, America/Port_of_Spain, Antarctica/DumontDUrville, and
Antarctica/Syowa.

Changes to documentation

tzfile.5 better matches a draft successor to RFC 8536
https://datatracker.ietf.org/doc/draft-murchison-rfc8536bis/01/.

2021.2: Release of upstream tzdata 2021b

Version 2021.2

Upstream version 2021b released 2021-09-24T23:23:00+00:00

Briefly:

This is an intermediate release that cherry-picks only the changes to Jordan and
Samoa's DST. It will not match upstream 2021b, which includes many other
changes.

Changes to future timestamps

Jordan now starts DST on February's last Thursday. (Thanks to Steffen Thorsen.)

Samoa no longer observes DST. (Thanks to Geoffrey D. Bennett.)

2021.1: Release of tzdata 2021a

Version 2021.1

Upstream version 2021a released 2021-01-24T18:54:57+00:00

Changes to future timestamps

South Sudan changes from +03 to +02 on 2021-02-01 at 00:00. (Thanks to Steffen
Thorsen.)

2020.5: Release of tzdata 2020e

Version 2020.5

Upstream version 2020e released 2020-12-22T23:14:34+00:00

Briefly:

Volgograd switches to Moscow time on 2020-12-27 at 02:00.

Changes to future timestamps

Volgograd changes time zone from +04 to +03 on 2020-12-27 at 02:00. (Thanks to
Alexander Krivenyshev and Stepan Golosunov.)

Changes to past timestamps

Correct many pre-1986 transitions, fixing entries originally derived from
Shanks. The fixes include:

• Australia: several 1917 through 1971 transitions
• Bahamas: several 1941 through 1945 transitions
• Bermuda: several 1917 through 1956 transitions
• Belize: several 1942 through 1968 transitions
• Ghana: several 1915 through 1956 transitions
• Israel and Palestine: several 1940 through 1985 transitions
• Kenya and adjacent: several 1908 through 1960 transitions
• Nigeria and adjacent: correcting LMT in Lagos, and several 1905 through 1919 transitions
• Seychelles: the introduction of standard time in 1907, not 1906
• Vanuatu: DST in 1973-1974, and a corrected 1984 transition

(Thanks to P Chan.)

Because of the Australia change, Australia/Currie (King Island) is no longer
needed, as it is identical to Australia/Hobart for all timestamps since 1970 and
was therefore created by mistake. Australia/Currie has been moved to the
'backward' file and its corrected data moved to the 'backzone' file.

Changes to past time zone abbreviations and DST flags

To better match legislation in Turks and Caicos, the 2015 shift to year-round
observance of -04 is now modeled as AST throughout before returning to Eastern
Time with US DST in 2018, rather than as maintaining EDT until 2015-11-01.
(Thanks to P Chan.)

Changes to documentation

The zic man page now documents zic's coalescing of transitions when a zone falls
back just before DST springs forward.

2020.4: Release of tzdata 2020d

Version 2020.4

Upstream version 2020d released 2020-10-21T18:24:13+00:00

Briefly:

Palestine ends DST earlier than predicted, on 2020-10-24.

Changes to past and future timestamps

Palestine ends DST on 2020-10-24 at 01:00, instead of 2020-10-31 as previously
predicted (thanks to Sharef Mustafa.) Its 2019-10-26 fall-back was at 00:00,
not 01:00 (thanks to Steffen Thorsen.) Its 2015-10-23 transition was at 01:00
not 00:00, and its spring 2020 transition was on March 28 at 00:00, not March 27
(thanks to Pierre Cashon.) This affects Asia/Gaza and Asia/Hebron. Assume
future spring and fall transitions will be on the Saturday preceding the last
Sunday of March and October, respectively.

2020.3: Release of tzdata 2020c

Relevant portion of the upstream changelog:

Release 2020c - 2020-10-16 11:15:53 -0700

Briefly:

Fiji starts DST later than usual, on 2020-12-20.

Changes to future timestamps

Fiji will start DST on 2020-12-20, instead of 2020-11-08 as
previously predicted. DST will still end on 2021-01-17.
(Thanks to Raymond Kumar and Alan Mintz.) Assume for now that
the later-than-usual start date is a one-time departure from the
recent pattern.

2020.2: Release of tzdata 2020b

Upstream changelog contents (only the data-related aspects of this apply):

Release notes are:

Briefly:
Revised predictions for Morocco's changes starting in 2023.
Canada's Yukon changes to -07 on 2020-11-01, not 2020-03-08.
Macquarie Island has stayed in sync with Tasmania since 2011.
Casey, Antarctica is at +08 in winter and +11 in summer.
zic no longer supports -y, nor the TYPE field of Rules.

Changes to future timestamps

Morocco's spring-forward after Ramadan is now predicted to occur
no sooner than two days after Ramadan, instead of one day.
(Thanks to Milamber.)  The first altered prediction is for 2023,
now predicted to spring-forward on April 30 instead of April 23.

Changes to past and future timestamps

Casey Station, Antarctica has been using +08 in winter and +11 in
summer since 2018. The most recent transition from +08 to +11 was
2020-10-04 00:01. Also, Macquarie Island has been staying in
sync with Tasmania since 2011. (Thanks to Steffen Thorsen.)

Changes to past and future time zone abbreviations and DST flags

Canada's Yukon, represented by America/Whitehorse and
America/Dawson, changes its time zone rules from -08/-07 to
permanent -07 on 2020-11-01, not on 2020-03-08 as 2020a had it.
This change affects only the time zone abbreviation (MST vs PDT)
and daylight saving flag for the period between the two dates.
(Thanks to Andrew G. Smith.)

Changes to past timestamps

Correct several transitions for Hungary for 1918/1983.
For example, the 1983-09-25 fall-back was at 01:00, not 03:00.
(Thanks to Géza Nyáry.)  Also, the 1890 transition to standard
time was on 11-01, not 10-01 (thanks to Michael Deckers).

The 1891 French transition was on March 16, not March 15.  The
1911-03-11 French transition was at midnight, not a minute later.
Monaco's transitions were on 1892-06-01 and 1911-03-29, not
1891-03-15 and 1911-03-11.  (Thanks to Michael Deckers.)

Changes to code

Support for zic's long-obsolete '-y YEARISTYPE' option has been
removed and, with it, so has support for the TYPE field in Rule
lines, which is now reserved for compatibility with earlier zic.
These features were previously deprecated in release 2015f.
(Thanks to Tim Parenti.)

zic now defaults to '-b slim' instead of to '-b fat'.

zic's new '-l -' and '-p -' options uninstall any existing
localtime and posixrules files, respectively.

The undocumented and ineffective tzsetwall function has been
removed.

Changes to build procedure

The Makefile now defaults POSIXRULES to '-', so the posixrules
feature (obsolete as of 2019b) is no longer installed by default.

Changes to documentation and commentary

The long-obsolete files pacificnew, systemv, and yearistype.sh have
been removed from the distribution.  (Thanks to Tim Parenti.)

2020.1: Release of tzdata 2020a

This release includes the IANA database version 2020a. It does not include the posix/ and right/ subdirectories.

2020.1rc1: Release Candidate 1 for 2020a

This release removes the posixrules zone.

2020.1rc0: Release Candidate 0 for 2020a

First release candidate for the 2020a IANA time zone data.