[tz] Single source of truth for timezone data

[Almaz Mingaleev]

Does that mean that libc APIs will behave differently from whatever
is using ICU files?

On Android we are waiting for ICU/CLDR patches because we offer
libc, ICU, and several Java APIs.

I believe Apple also waits for ICU/CLDR patches, though I do not know
their reasons.

On Fri, 2 Dec 2022 at 17:25, Benjamin Drung via tz <tz at iana.org> wrote:

> Hi everyone,
>
> I am writing this mail with my distribution maintainer hat on since I am
> responsible for keeping the tzdata package up-to-date in Ubuntu. I like
> to propose to have a single source of truth for timezone data, which
> should be the tzdata source package. Updating this package in a
> distribution like Debian/Ubuntu should be enough to update all consumers
> in the distribution.
>
> Sadly this is currently not the case. Ubuntu since 20.04 (focal) adds
> the four icu source files metaZones.txt, timezoneTypes.txt,
> windowsZones.txt, and zoneinfo64.txt from
> https://github.com/unicode-org/icu-data to the tzdata source package.
> Then it uses genrb and icupkg to generate the .res files. Since the icu
> project lacks behind the tzdata release by hours up to days, Ubuntu has
> to update tzdata twice (first the tzdata release, then the icu update).
>
> metaZones.txt, timezoneTypes.txt, and windowsZones.txt are generated
> using tools/cldr/cldr-to-icu/build-icu-data.xml from
> https://github.com/unicode-org/icu. zoneinfo64.txt is generated by
> tz2icu. build-icu-data.xml uses https://github.com/unicode-org/cldr as
> input to convert the cldr data to icu. If I saw that correctly, only
> common/supplemental/metaZones.xml needs to be updated there on an
> update.
>
> Can tzdata include the necessary data and tools to generate
> metaZones.xml from its source? Then it would be possible to generate the
> icu data from the tzdata source without the need to wait for icu to
> catch up. Then Debian/Ubuntu can ship a tzdata-icu package for it [1].
>
> [1] https://bugs.debian.org/954112
>
> --
> Benjamin Drung
> Debian & Ubuntu Developer
>
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