Bug#1143499: America/Vancounter PDT change in tzdata breaks gmtime(3)

On Mon, Aug 03, 2026 at 11:42:16PM +0200, Aurelien Jarno wrote:

> The main issue is there. gmtime() returns a tm structure with tm_isdst 
> set to 0, which is not correct as the time (at least when executed 
> currently) includes a DST. With the previous tzdata version, the 
> mktime heuristics were able to fix it, but it is not the case anymore for
> dates after 2026-06-06). It is not clear yet why.

Paul Eggert made the Vancouver change on March 3. Robert Bastian of Unicode CLDR
complained that the change stepped on CLDR's use of tm_isdst (which Eggert and -
I think - POSIX consider deprecated). This gave rise to a long thread, and
ultimately the installation of a temporary hack to accomodate CLDR in TZDB until
they can make a release in autumn.

I've chedked; the removal of that hack (committed on March 7) makes Mason's code work.

I don't know what the CLDR status is, but there will probably be some discussion of it
on the TZDB mailing list now.

/Lars