The WMF production Debian Buster servers appear to have tzdata 2021a-0+deb10u12 installed. The changelog for this package does not appear to include Kazakhstan DST changes later than:

Release 2018h - 2018-12-23 17:59:32 -0800

  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.

I looks like tzdata (2024a-1), currently available in https://packages.debian.org/trixie/tzdata, is the first release to include the needed changes.

Hey, @MoritzMuehlenhoff this is something that if it is trivial I can handle as clinic duty, but I would like your opinion/coordination as our resident Debian expert first and has handled basic package/i18n infra needs in the past (or anyone else on IF).

The latest Bookworm tzdata package already have the updated timezone for Kazakhstan as well, maybe we can just backport that one.

Buster is still supported by the Debian LTS project and tzdata has recently been added to the list of packages to be updated:
https://salsa.debian.org/security-tracker-team/security-tracker/-/blob/master/data/dla-needed.txt?ref_type=heads#L285

When that update has been released, it will be rolled out automatically to our servers.

While the time in Almaty and Kostanai is still UTC+6, apparently not everything has been updated. @MoritzMuehlenhoff

@MuratKaribay Can you please retry? I just tested changing the timezone to Almaty and Kostanai and it gave me a five hour offset.

(We are currently transitioning the way the wiki traffic is served (more details at https://wikitech.wikimedia.org/wiki/MediaWiki_On_Kubernetes) and while the servers serving the old scheme were updated last week, the percentage of traffic serving the new system only updated the timezone data yesterday, so you probably hit the latter earlier)