Version 2023.4

Upstream version 2023d released 2023-12-22T04:02:24+00:00

Briefly:

Ittoqqortoormiit, Greenland changes time zones on 2024-03-31. Vostok, Antarctica
changed time zones on 2023-12-18. Casey, Antarctica changed time zones five
times since 2020. Code and data fixes for Palestine timestamps starting in 2072.
A new data file zonenow.tab for timestamps starting now.

Changes to future timestamps

Ittoqqortoormiit, Greenland (America/Scoresbysund) joins most of the rest of
Greenland's timekeeping practice on 2024-03-31, by changing its time zone from
-01/+00 to -02/-01 at the same moment as the spring-forward transition. Its
clocks will therefore not spring forward as previously scheduled. The time zone
change reverts to its common practice before 1981.

Fix predictions for DST transitions in Palestine in 2072-2075, correcting a typo
introduced in 2023a.

Changes to past and future timestamps

Vostok, Antarctica changed to +05 on 2023-12-18. It had been at +07 (not +06)
for years. (Thanks to Zakhary V. Akulov.)

Change data for Casey, Antarctica to agree with timeanddate.com, by adding five
time zone changes since 2020. Casey is now at +08 instead of +11.

Changes to past tm_isdst flags

Much of Greenland, represented by America/Nuuk, changed its standard time from
-03 to -02 on 2023-03-25, not on 2023-10-28. This does not affect UTC offsets,
only the tm_isdst flag. (Thanks to Thomas M. Steenholdt.)

New data file

A new data file zonenow.tab helps configure applications that use timestamps
dated from now on. This simplifies configuration, since users choose from a
smaller Zone set. The file's format is experimental and subject to change.

Changes to commentary

Limitations and hazards of the optional support for obsolescent C89 platforms
are documented better, along with a tentative schedule for removing this
support.