Update Time Zone Data for ZoneParser
Note: This is usually done as a part of full time zone data update process.
1. Download the latest version of IANA Time Zone Database page: https://www.iana.org/time-zones
There are 3 links available for latest version. Select the complete distribution tzdb-<version>.tar.lz (e.g. tzdb-2021a.tar.lz).
Extract entire contents to a work directory.
Note: The data only distribution contains minimum set of files you really need. However, you cannot use a convenient make target without codes. The complete distribution package contains the codes.
2. Run make target - rearguard_tarballs_version
This target creates "rearguard" version of zoneinfo files under directory: tzdataunknown-rearguard.dir.
Note: If you specify a version (e.g. VERSION=2021) when invoking the target, "unknown" will be replaced with the specified version (e.g. tzdata2021a-rearguard.dir), but it's not important in this instruction.
A standard zoneinfo file may use negative daylight saving time offsets. CLDR code currently can not handle negative daylight saving time offsets. The "rearguard" version is designed for tools without negative daylight saving time support.
3. Copy files generated by previous step to {CLDR_DIR}/tools/cldr-code/src/main/resources/org/unicode/cldr/util/data
Below the list of files to be include:
africa
antarctica
asia
australasia
backward
etcetera
europe
leapseconds
northamerica
southamerica
zone.tab
Note: leapseconds might be removed from the list later.
4. Edit the file {CLDR_DIR}}/tools/cldr-code/src/main/resources/org/unicode/cldr/util/data/tzdb-version.txt
This file contains just one line text specifying a version of Time Zone Database, e.g. 2021a.
5. Record the version: See Updating External Metadata