ICU-23296 Update tzdata to 2025c

[eggrobin]

No description provided.

[robertbastian]

these are changes from CLDR 48, did we miss a step during integration?

[eggrobin]

The same kind of drive-by picking up of CLDR changes seems to have happened in #34, so it’s not clear that this has consistently been an integration step. But perhaps it should be.

[robertbastian]

Ah is this only patch data? So ICU 78 shipped with a TZDB 2025b, and clients didn't use the 2025b data from this repo?

[eggrobin]

I think so, but I cannot say I am familiar with the architecture here. @markusicu, do you know who uses this (apart from us as part of the process of picking up a new TZDB for unicode-org/icu)?

[markusicu]

Users of ICU need to be able to update the time zone data without having to update ICU, so for many years we have published the data here.

See https://unicode-org.github.io/icu/userguide/datetime/timezone/#updating-the-time-zone-data

[markusicu]

these are changes from CLDR 48, did we miss a step during integration?

The last update was for 2025b, done by @Yqwed in #45 in 2025-apr. I guess we only update this file in this repo when there is a new tzdata version, not whenever CLDR changes.

[eggrobin]

I guess we only update this file in this repo when there is a new tzdata version, not whenever CLDR changes.

Should we update it when CLDR changes? (This seems like the same misalignment in process that led to the comprehensive round-trip tests failing: the timezone update process isn’t followed when we update CLDR’s timezone-related data.)

[markusicu]

rslgtm