[tz] [musl] Re: [musl] Re: Weird PST8PDT and EST5EDT behavior on Alpine Linux

[Rich Felker]

On Tue, Mar 05, 2024 at 04:47:02PM -0800, Paul Eggert wrote:
> On 3/5/24 12:12, Rich Felker via tz wrote:
> >Yes, it's not clear to me (POSIX doesn't seem to specify) what the
> >default rules should be when none are specified. However, it is clear
> >that these strings meet the syntax for the POSIX TZ form, and thus
> >musl does not attempt to interpret them as filenames, which could
> >result in behavior contrary to the specified meaning.
> 
> Although TZDB interprets them as filenames, that is OK because the
> TZDB filenames have the specified meaning. Each TZDB Zone whose name
> has the form of a POSIX.1-2017 TZ string implements a set of
> transitions compatible with the corresponding POSIX TZ setting.
> 
> Long ago that wasn't the case: there were Zones like "GMT-12" that
> weren't compatible with POSIX even though their names took the POSIX
> forms. But that bug was fixed decades ago, in tzdata 94d
> (1994-02-24), and we no longer need to worry about that possibility.

Interesting idea we could consider: if the TZ string matches POSIX
format for a zone with DST but without any rule portion, load a file
and accept it if the zones are consistent (all name/offset pairs
match) -- so that it's effectively just defining the transition date
rules.

Rich