tzdata-2019b

[Bruce Dubbs]

New version.

[Bruce Dubbs]

News for the tz database

Release 2019b - 2019-07-01 00:09:53 -0700

Briefly:

Brazil no longer observes DST. 'zic -b slim' outputs smaller TZif files; please try it out. Palestine's 2019 spring-forward transition was on 03-29, not 03-30.

Changes to future timestamps

Brazil has canceled DST and will stay on standard time indefinitely. (Thanks to Steffen Thorsen, Marcus Diniz, and Daniel Soares de Oliveira.)

Predictions for Morocco now go through 2087 instead of 2037, to work around a problem on newlib when using TZif files output by zic 2019a or earlier. (Problem reported by David Gauchard.)

Changes to past and future timestamps

Palestine's 2019 spring transition was 03-29 at 00:00, not 03-30 at 01:00. (Thanks to Sharef Mustafa and Even Scharning.) Guess future transitions to be March's last Friday at 00:00.

Changes to past timestamps

Hong Kong's 1941-06-15 spring-forward transition was at 03:00, not 03:30. Its 1945 transition from JST to HKT was on 11-18 at 02:00, not 09-15 at 00:00. In 1946 its spring-forward transition was on 04-21 at 00:00, not the previous day at 03:30. From 1946 through 1952 its fall-back transitions occurred at 04:30, not at 03:30. In 1947 its fall-back transition was on 11-30, not 12-30. (Thanks to P Chan.)

Changes to past time zone abbreviations

Italy's 1866 transition to Rome Mean Time was on December 12, not September 22. This affects only the time zone abbreviation for Europe/Rome between those dates. (Thanks to Stephen Trainor and Luigi Rosa.)

Changes affecting metadata only

Add info about the Crimea situation in zone1970.tab and zone.tab. (Problem reported by Serhii Demediuk.)

Changes to code

zic's new -b option supports a way to control data bloat and to test for year-2038 bugs in software that reads TZif files. 'zic -b fat' and 'zic -b slim' generate larger and smaller output; for example, changing from fat to slim shrinks the Europe/London file from 3648 to 1599 bytes, saving about 56%. Fat and slim files represent the same set of timestamps and use the same TZif format as documented in tzfile(5) and in Internet RFC 8536. Fat format attempts to work around bugs or incompatibilities in older software, notably software that mishandles 64-bit TZif data or uses obsolete TZ strings like "EET-2EEST" that lack DST rules. Slim format is more efficient and does not work around 64-bit bugs or obsolete TZ strings. Currently zic defaults to fat format unless you compile with -DZIC_BLOAT_DEFAULT=\"slim\"; this out-of-the-box default is intended to change in future releases as the buggy software often mishandles timestamps anyway.

zic no longer treats a set of rules ending in 2037 specially. Previously, zic assumed that such a ruleset meant that future timestamps could not be predicted, and therefore omitted a POSIX-like TZ string in the TZif output. The old behavior is no longer needed for current tzdata, and caused problems with newlib when used with older tzdata (reported by David Gauchard).

zic no longer generates some artifact transitions. For example, Europe/London no longer has a no-op transition in January 1996.

Changes to build procedure

tzdata.zi now assumes zic 2017c or later. This shrinks tzdata.zi by a percent or so.

Changes to documentation and commentary

The Makefile now documents the POSIXRULES macro as being obsolete, and similarly, zic's -p POSIXRULES option is now documented as being obsolete. Although the POSIXRULES feature still exists and works as before, in practice it is rarely used for its intended purpose, and it does not work either in the default reference implementation (for timestamps after 2037) or in common implementations such as GNU/Linux (for contemporary timestamps). Since POSIXRULES was designed primarily as a temporary transition facility for System V platforms that died off decades ago, it is being decommissioned rather than institutionalized.

New info on Bonin Islands and Marcus (thanks to Wakaba and Phake Nick).

[Bruce Dubbs]

Fixed at revision 11639.