(tz) Upgrade time-zone data to tzdata2018h

[Sat Dec 29 23:07:37 UTC 2018]

The 2018h 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:
     Qyzylorda, Kazakhstan moved from +06 to +05 on 2018-12-21.
     New zone Asia/Qostanay because Qostanay, Kazakhstan didn't move.
     Metlakatla, Alaska observes PST this winter only.
     Guess Morocco will continue to adjust clocks around Ramadan.
     Add predictions for Iran from 2038 through 2090.

   Changes to future timestamps

     Guess that Morocco will continue to fall back just before and
     spring forward just after Ramadan, the practice since 2012.
     (Thanks to Maamar Abdelkader.) This means Morocco will observe
     negative DST during Ramadan in main and vanguard formats, and in
     rearguard format it stays in the +00 timezone and observes
     ordinary DST in all months other than Ramadan. As before, extend
     this guesswork to the year 2037. As a consequence, Morocco is
     scheduled to observe three DST transitions in some Gregorian years
     (e.g., 2033) due to the mismatch between the Gregorian and Islamic
     calendars.

     The table of exact transitions for Iranian DST has been extended.
     It formerly cut off before the year 2038 in a nod to 32-bit time_t.
     It now cuts off before 2091 as there is doubt about how the Persian
     calendar will treat 2091. This change predicts DST transitions in
     2038-9, 2042-3, and 2046-7 to occur one day later than previously
     predicted. As before, post-cutoff transitions are approximated.

   Changes to past and future timestamps

     Qyzylorda (aka Kyzylorda) oblast in Kazakhstan moved from +06 to
     +05 on 2018-12-21. This is a zone split as Qostanay (aka
     Kostanay) did not switch, so create a zone Asia/Qostanay.

     Metlakatla moved from Alaska to Pacific standard time on 2018-11-04.
     It did not change clocks that day and remains on -08 this winter.
     (Thanks to Ryan Stanley.) It will revert to the usual Alaska
     rules next spring, so this change affects only timestamps
     from 2018-11-04 through 2019-03-10.

   Change to past timestamps

     Kwajalein's 1993-08-20 transition from -12 to +12 was at 24:00,
     not 00:00. I transcribed the time incorrectly from Shanks.
     (Thanks to Phake Nick.)

     Nauru's 1979 transition was on 02-10 at 02:00, not 05-01 at 00:00.
     (Thanks to Phake Nick.)

     Guam observed DST irregularly from 1959 through 1977.
     (Thanks to Phake Nick.)

     Hong Kong observed DST in 1941 starting 06-15 (not 04-01), then on
     10-01 changed standard time to +08:30 (not +08). Its transition
     back to +08 after WWII was on 1945-09-15, not the previous day.
     Its 1904-10-30 change took effect at 01:00 +08 (not 00:00 LMT).
     (Thanks to Phake Nick, Steve Allen, and Joseph Myers.) Also,
     its 1952 fallback was on 11-02 (not 10-25).

     This release contains many changes to timestamps before 1946 due
     to Japanese possession or occupation of Pacific/Chuuk,
     Pacific/Guam, Pacific/Kosrae, Pacific/Kwajalein, Pacific/Majuro,
     Pacific/Nauru, Pacific/Palau, and Pacific/Pohnpei.
     (Thanks to Phake Nick.)

     Assume that the Spanish East Indies was like the Philippines and
     observed American time until the end of 1844. This affects
     Pacific/Chuuk, Pacific/Kosrae, Pacific/Palau, and Pacific/Pohnpei.

   Changes to past tm_isdst flags

     For the recent Morocco change, the tm_isdst flag should be 1 from
     2018-10-27 00:00 to 2018-10-28 03:00. (Thanks to Michael Deckers.)
     Give a URL to the official decree. (Thanks to Matt Johnson.)

Here are links to the release files:

   https://www.iana.org/time-zones/repository/releases/tzcode2018h.tar.gz
   https://www.iana.org/time-zones/repository/releases/tzdata2018h.tar.gz
   https://www.iana.org/time-zones/repository/releases/tzdb-2018h.tar.lz


Links are also available via plain HTTP, and via FTP from
ftp://ftp.iana.org/tz/releases with the same basenames as above.


PS. If your tzdata parser does not yet support negative DST offsets,
this particular release's data entries are also available in a
rearguard-format tarball and signature that does not contain such
offsets. This is intended to be a temporary transition aid for these
parsers. The URLs are:

https://web.cs.ucla.edu/~eggert/tz/release/2018h/tzdata2018h-rearguard.tar.gz
https://web.cs.ucla.edu/~eggert/tz/release/2018h/tzdata2018h-rearguard.tar.gz.asc