1### 2022a 2 3This update includes pre-1970 4[changes](https://github.com/eggert/tz/commit/1edbb16e933a6ba6dceefd2bd7057b5ce00dd13c) 5which were reverted manually in Android and resulted in Android releasing 6updates we called `2021a rev 2` and `2021a rev 3` instead of tracking TZDB's 7`2021b` and `2021c` releases. Android has made changes to reduce the impact of 8these changes. This might have app compat issues as some methods in Android's 9ICU4J APIs such as `TimeZone.getCanonicalID(id)` will return different time 10zone IDs than before. After this release, the canonical zone IDs returned will 11be different for some input IDs, and will more often be associated with 12different regions. 13 14`Africa/Casablanca` is a time zone modelled by the TZDB using a negative DST 15saving to represent the period of Ramadan. Several of Android's embedded time 16libraries do not support negative DST savings, so we use TZDB's rearguard 17format, which flips standard and daylight saving time definitions for affected 18zones. Also, `Africa/Casablanca` transitions follow lunar calendar, which 19is not supported by TZif format so transitions are pre-generated (as of now up 20to year 2087). As they are pre-generated, the last transition is used for dates 21after 2087. Before `2022a`, in rearguard format that last transition was from 22standard to daylight saving time. Having DST throughout the year might break 23assumptions in software, so as of `2022a` the last transition is marked as 24standard time, even though its offset differs from standard time offset used in 25prior transitions. 26 27A standard-to-standard time transition breaks DST saving logic in 28Android's `java.util.TimeZone.getDSTSavings()` - it returns 0 instead of 1 hour. 29`input_data/iana/tzdb2022a.tar.gz` has [commit](https://github.com/eggert/tz/commit/cec7d9e2e83f8a3faa2367e0d45383a1557889ed) 30reverted to bring back the old TZif file. There is no fix yet, it will be like 31that indefinitely. 32 33The main reason for the TZDB `2022a` release is a change to the DST transition 34for Palestine on 27 Mar 2022. In addition to this year's change, future 35predictions have also been [adjusted](https://github.com/eggert/tz/commit/59467e3373a2f90aae3a3c9684ab527855922427) 36so the DST transitions for future years are also affected. 37 38 39### 2021 rev. 3 40 41Like 2021 rev.2 this release is also different from regular updates. It is 42closely correlated with IANA's `2021d` and `2021e`. See below for more details. 43 44TZDB version `2021c` reverted most (but not all) time zone merges from `2021b`. 45As Android has not applied any of them and there were no other rules update, 46it is a no-op for Android. 47 48Then TZDB version `2021d` was released with Fiji changes. That corresponds to 49ICU's `2021a2`. But `2021a2` also picked up a 50`"Link America/Panama America/Coral_Harbour"` change from IANA's TZDB release 51in the backward file. 52 53ICU's `2021a3` is `2021a2` with Palestine changes. No extra change there. 54 55`tzdata2021a.tar.gz` in this Android TZDB update is ICU's [`tzdata2021a3.tar.gz`](https://github.com/unicode-org/icu-data/blob/d90a4eed92e3c5221c4dc1977bfdb7c072a8bb3d/tzdata/tzdata_patch/tzdata2021a3.tar.gz) 56with `Link` change mention above reverted. Not reverting it will put 57`America/Coral_Harbour` under Panama in `tzlookup.xml`. Right approach here 58is to update tooling, but that will take some time. 59 60 61### 2021a rev. 2 62 63In `2021b` several time zones which were alike since 1970 were merged. It 64received backlash in tz mailing-list. Please check 65[September archive](https://mm.icann.org/pipermail/tz/2021-September/thread.html) 66for discussions around the merges. 67 68This contains a subset of the updates from IANA's 2021b update, but not all 69because they cause problems for various libraries and OSes, Android included. 70New links cause problems for the tzlookup.xml generation process, which have 71yet to be resolved. Android API behavior is influenced by ICU, so while ICU 72are forked and until things become clearer, so is Android. 73 74ICU decided to skip zone merge changes and named their release `2021a1`. 75Unfortunately there are hardcoded places in Android which expect tzdb version 76to be exactly 5 characters and we release it as `2021a rev. 2`. 77 78`input_data/iana/tzdata2021a.tar.gz` is renamed ICU's `2021a1.tar.gz`. As it 79is not signed, `tzdata2021a.tar.gz.asc` was deleted for this release only. 80 81`2021a1` contains the following changes applied on top of `2021a`: 82``` 83# Portugal observed DST in 1950 84https://github.com/eggert/tz/commit/ed2f9d6b01d1256a4d463d2ceb953e15e1673d72 85# Fix Guyana LMT and later historical transitions 86https://github.com/eggert/tz/commit/0252f09cdff3769ecbf6adfdaf6c47055bbfb74b 87# Add Barbados DST 1942-1944, fix end of LMT 88https://github.com/eggert/tz/commit/42efb563b8224a20c1a6480b38427e5b4634da36 89# Backzone fixes for Gambia, Malawi, Sierra Leone 90https://github.com/eggert/tz/commit/bdb47c5fd68996c04a69d6b23c4c4a5a81df5c95 91# Sierra Leone did not use DST 1957-1962 92https://github.com/eggert/tz/commit/6982e34ab92cf13f3f3fb20212aca8aa2e4f0aae 93# Tonga moved from +12:20 to +13 in 1961, not 1941 94https://github.com/eggert/tz/commit/666022ef2a65bb9872ffa6d98cb73236c5f6daa0 95# Tonga switched to standard time in 1945, not 1901 96https://github.com/eggert/tz/commit/03cc98977ea7c93c49ecb58eae07cd01e9034bfd 97# Cook Islands had two Christmases in 1899 98https://github.com/eggert/tz/commit/bf12c3ba8513b640b83c245f804c37feeccb862b 99# More pre-1978 fixes for Cook and Niue 100https://github.com/eggert/tz/commit/a10451bb3fa7f84181f29ac81b06008fd1d81249 101# Fix north Vietnam lat+long 102https://github.com/eggert/tz/commit/6860c875400b70be52c71d7b7b9642b8667a8112 103# Niue left -11:20 in 1964, not 1978 104https://github.com/eggert/tz/commit/b73f9fd0364e1795b40cd325661ce609d6126377 105# Samoa no longer observes DST 106https://github.com/eggert/tz/commit/29583c461a9705118560e02e69bb64a0bf2fce0c 107# Jordan now starts DST on February’s last Thursday. 108https://github.com/eggert/tz/commit/39df8c8b22605f59f71213cfb92b3fd321e31d3c 109``` 110 111These changes are in chronological order -- from old to new, so apply them 112accordingly. 113 114"Replace Pacific/Enderbury with Pacific/Kanton" change was skipped as it 115requires changes in CLDR and `tzdb2021b` was announced late in CLDR's release 116cycle. 117 118Code changes were skipped as Android uses fixed version of tzcode, not ToT. 119 120