Since introduction of Europe/Kyiv (2022b, 10 Aug 2022) we were carrying local patch: Europe/Kyiv in zone.tab is renamed back to Europe/Kiev as alternative names are not supported in this release and there are no ICU translations for Europe/Kyiv. Doing so has no visible effect on users as we do not expose Olson IDs and these time zones are identical.
TZDB 2022b introduces Europe/Kyiv and merges more time zones which were
alike since 1970. These changes require ICU patches.
Though the reason why 2022b was released are changes in Chile. As they have to be delivered by the 3rd of September and ICU patches are not ready, decision was made to prepare smaller release which does not need ICU patches.
tzdata archieve is prepared manually by applying Iran and Chile changes on top of 2022a tag.
Like 2021a rev.2 this release is also different from regular updates. It is
closely correlated with IANA's 2021d and 2021e. See below for more details.
TZDB version 2021c reverted most (but not all) time zone merges from 2021b.
As Android has not applied any of them and there were no other rules update,
it is a no-op for Android.
Then TZDB version 2021d was released with Fiji changes. That corresponds to
ICU's 2021a2. But 2021a2 also picked up a
"Link America/Panama America/Coral_Harbour" change from IANA's TZDB release
in the backward file.
ICU's 2021a3 is 2021a2 with Palestine changes. No extra change there.
tzdata2021a.tar.gz in this Android TZDB update is ICU's tzdata2021a3.tar.gz
with Link change mention above reverted. Not reverting it will put
America/Coral_Harbour under Panama in tzlookup.xml. Right approach here
is to update tooling, but that will take some time.
In 2021b several time zones which were alike since 1970 were merged. It
received backlash in tz mailing-list. Please check
September archive
for discussions around the merges.
This contains a subset of the updates from IANA's 2021b update, but not all because they cause problems for various libraries and OSes, Android included. New links cause problems for the tzlookup.xml generation process, which have yet to be resolved. Android API behavior is influenced by ICU, so while ICU are forked and until things become clearer, so is Android.
ICU decided to skip zone merge changes and named their release 2021a1.
Unfortunately there are hardcoded places in Android which expect tzdb version
to be exactly 5 characters and we release it as 2021a rev. 2.
input_data/iana/tzdata2021a.tar.gz is renamed ICU's 2021a1.tar.gz. As it
is not signed, tzdata2021a.tar.gz.asc was deleted for this release only.
2021a1 contains the following changes applied on top of 2021a:
# Portugal observed DST in 1950
https://github.com/eggert/tz/commit/ed2f9d6b01d1256a4d463d2ceb953e15e1673d72
# Fix Guyana LMT and later historical transitions
https://github.com/eggert/tz/commit/0252f09cdff3769ecbf6adfdaf6c47055bbfb74b
# Add Barbados DST 1942-1944, fix end of LMT
https://github.com/eggert/tz/commit/42efb563b8224a20c1a6480b38427e5b4634da36
# Backzone fixes for Gambia, Malawi, Sierra Leone
https://github.com/eggert/tz/commit/bdb47c5fd68996c04a69d6b23c4c4a5a81df5c95
# Sierra Leone did not use DST 1957-1962
https://github.com/eggert/tz/commit/6982e34ab92cf13f3f3fb20212aca8aa2e4f0aae
# Tonga moved from +12:20 to +13 in 1961, not 1941
https://github.com/eggert/tz/commit/666022ef2a65bb9872ffa6d98cb73236c5f6daa0
# Tonga switched to standard time in 1945, not 1901
https://github.com/eggert/tz/commit/03cc98977ea7c93c49ecb58eae07cd01e9034bfd
# Cook Islands had two Christmases in 1899
https://github.com/eggert/tz/commit/bf12c3ba8513b640b83c245f804c37feeccb862b
# More pre-1978 fixes for Cook and Niue
https://github.com/eggert/tz/commit/a10451bb3fa7f84181f29ac81b06008fd1d81249
# Fix north Vietnam lat+long
https://github.com/eggert/tz/commit/6860c875400b70be52c71d7b7b9642b8667a8112
# Niue left -11:20 in 1964, not 1978
https://github.com/eggert/tz/commit/b73f9fd0364e1795b40cd325661ce609d6126377
# Samoa no longer observes DST
https://github.com/eggert/tz/commit/29583c461a9705118560e02e69bb64a0bf2fce0c
# Jordan now starts DST on February’s last Thursday.
https://github.com/eggert/tz/commit/39df8c8b22605f59f71213cfb92b3fd321e31d3c
These changes are in chronological order -- from old to new, so apply them accordingly.
"Replace Pacific/Enderbury with Pacific/Kanton" change was skipped as it
requires changes in CLDR and tzdb2021b was announced late in CLDR's release
cycle.
Code changes were skipped as Android uses fixed version of tzcode, not ToT.