On 2026-03-04 02:51:11 (+0800), Paul Eggert via tz wrote:
Thanks for the heads-up. I talked about this with Tim. Proposed patch
attached. We'll need a new TZDB release soon.
I see two issues with the BC change.
Legally, 21 hours after the long-planned 2026-03-08 02:00 transition
from PST to PDT, this change introduces a new transition from PDT to
Pacific Time that alters the tm_isdst flag and likely the abbreviation
but does not alter the UT offset. A 21-hour gap between two
transitions is small, so initially I thought of modeling things with a
single transition. However, zic and zdump work fine with a 21-hour gap
so the attached proposed patch follows the letter of the law rather
than simplifying it.
No matter what abbreviation we use, there will be trouble. The obvious
abbreviation PT does not conform to the POSIX standard or to TZDB
guidelines, as it is one letter too short. The alphabetic abbreviation
least likely to break existing software is "MST", but that clashes
with the name "Pacific Time". The attached patch suggests some other
possibilities. I asked the BC government for guidance; if they do not
have a helpful suggestion I suspect "MST" will be the best of a bad
lot of alphabetic abbreviations, due to software compatibility issues.
In the meantime I installed into the development repository the
proposed patch, which uses a "-07" placeholder that also should work
but is jarring in a North American context.
Comments welcome of course.
What's wrong with "-07"? That's what's used in other parts of the
world. Why is North America exceptional?
I would suggest that CPST -- analogous to AEST -- is probably a better
choice if "-07" won't do for some reason.
Philip
