During the trixie cycle, the tzdata package reduced the set of timezone
files that it ships, moving many of them to tzdata-legacy on the basis
that the upstream tz project considers them to be for backward
compatibility:

tzdata (2023c-8) unstable; urgency=medium

  [...]
  * Ship only timezones in tzdata that follow the current rules of geographical
    region (continent or ocean) and city name. Move all legacy timezone symlinks
    (that are upgraded during package update) to tzdata-legacy. This includes
    dropping the special handling for US/* timezones. (Closes: #1040997)

Control: forwarded -1 https://salsa.debian.org/ddp-team/release-notes/-/merge_requests/322
https://salsa.debian.org/ddp-team/release-notes/-/merge_requests/322

Review, improvements, notes, ... more than welcome!

Best,
Chris

This is now done, thanks to Chris Hofstaedtler:

https://www.debian.org/releases/stable/release-notes/issues.en.html#timezones-split-off-into-tzdata-legacy-package

Thanks,