On Thu, 29 May 2025 at 11:51, Doug Ewell via tz <tz@iana.org> wrote:
That isn’t what tz identifiers are for. They represent regions that have followed the same time zone rules (UTC offset, daylight-saving offset and dates) since 1970. They are not intended to identify locations with “distinct historical, geographic, and cultural identity.”

Doug articulates this correctly.  Quoting Point 1 in the "Rationale" section of Denis' linked proposal document:

1. Historical Time Zone Distinction:
  • Prior to 1982, Malaysia operated with two separate time zones:
    • West Malaysia (Peninsular): UTC+07:30
    • East Malaysia (Sabah & Sarawak): UTC+08:00
  • In 1982, the Malaysian government unified the time zones under UTC+08:00 nationwide. While this change brought West Malaysia ahead of its solar time, it was naturally aligned with Sabah's geographic solar noon.
Sabah & Sarawak have matched Brunei in staying on UTC+08:00 since before 1970, and so are already covered by Asia/Kuching.  Peninsular Malaysia shifted from UTC+07:30 to +08:00 at the same time as Singapore at the start of 1982, and so is already covered by Asia/Singapore.  Because both of these cases are already handled by our existing data, Point 1 forms a strong case for NOT creating a new zone.

Denis' Points 2 ("Geographical and Civil Uniqueness") and 3 ("Cultural Recognition and Technical Use") don't really factor into consideration for whether a separate zone is needed.  Please review:
https://data.iana.org/time-zones/data/theory.html
 
If you have or can provide evidence that Penampang or Kota Kinabalu has observed timekeeping rules in the period since 1970 that are not duplicated by other zones, please share that information.

This is the caveat as always.  If any region's wall-clock times from 1970 onward cannot be faithfully represented by existing zones, do let us know and be sure to provide links to reliable sources supporting such claims for our review.

--
Tim Parenti