Wind River Support Network

Description

The 2020a release of the tz code and data is available. It reflects the
 following changes, which were either circulated on the tz mailing list or are
 relatively minor technical or administrative changes:

Briefly:
 Morocco springs forward on 2020-05-31, not 2020-05-24.
 Canada's Yukon advanced to -07 year-round on 2020-03-08.
 America/Nuuk renamed from America/Godthab.
 zic now supports expiration dates for leap second lists.

Changes to future timestamps

Morocco's second spring-forward transition in 2020 will be May 31,
 not May 24 as predicted earlier. (Thanks to Semlali Naoufal.)
 Adjust future-year predictions to use the first Sunday after the
 day after Ramadan, not the first Sunday after Ramadan.

Canada's Yukon, represented by America/Whitehorse and
 America/Dawson, advanced to -07 year-round, beginning with its
 spring-forward transition on 2020-03-08, and will not fall back on
 2020-11-01. Although a government press release calls this
 "permanent Pacific Daylight Saving Time", we prefer MST for
 consistency with nearby Dawson Creek, Creston, and Fort Nelson.
 (Thanks to Tim Parenti.)

Changes to past timestamps

Shanghai observed DST in 1919. (Thanks to Phake Nick.)

Changes to timezone identifiers

To reflect current usage in English better, America/Godthab has
 been renamed to America/Nuuk. A backwards-compatibility link
 remains for the old name.

Changes to code

localtime.c no longer mishandles timestamps after the last
 transition in a TZif file with leap seconds and with daylight
 saving time transitions projected into the indefinite future.
 For example, with TZ='America/Los_Angeles' with leap seconds,
 zdump formerly reported a DST transition on 2038-03-14
 from 01:59:32.999... to 02:59:33 instead of the correct transition
 from 01:59:59.999... to 03:00:00.

zic -L now supports an Expires line in the leapseconds file, and
 truncates the TZif output accordingly. This propagates leap
 second expiration information into the TZif file, and avoids the
 abovementioned localtime.c bug as well as similar bugs present in
 many client implementations. If no Expires line is present, zic
 -L instead truncates the TZif output based on the #expires comment
 present in leapseconds files distributed by tzdb 2018f and later;
 however, this usage is obsolescent. For now, the distributed
 leapseconds file has an Expires line that is commented out, so
 that the file can be fed to older versions of zic which ignore the
 commented-out line. Future tzdb distributions are planned to
 contain a leapseconds file with an Expires line.

The configuration macros HAVE_TZNAME and USG_COMPAT should now be
 set to 1 if the system library supports the feature, and 2 if not.
 As before, these macros are nonzero if tzcode should support the
 feature, zero otherwise.

The configuration macro ALTZONE now has the same values with the
 same meaning as HAVE_TZNAME and USG_COMPAT.

The code's defense against CRLF in leap-seconds.list is now
 portable to POSIX awk. (Problem reported by Deborah Goldsmith.)

Although the undocumented tzsetwall function is not changed in
 this release, it is now deprecated in preparation for removal in
 future releases. Due to POSIX requirements, tzsetwall has not
 worked for some time. Any code that uses it should instead use
 tzalloc(NULL) or, if portability trumps thread-safety, should
 unset the TZ environment variable.

Changes to commentary

The Îles-de-la-Madeleine and the Listuguj reserve are noted as
 following America/Halifax, and comments about Yukon's "south" and
 "north" have been corrected to say "east" and "west". (Thanks to
 Jeffery Nichols.)

Here are links to the release files: 
 [https://www.iana.org/time-zones/repository/releases/tzcode2020a.tar.gz]

[https://www.iana.org/time-zones/repository/releases/tzdata2020a.tar.gz]

[https://www.iana.org/time-zones/repository/releases/tzdb-2020a.tar.lz]