[tz] Beginner's help request

Zefram zefram at fysh.org
Mon Oct 16 09:58:37 UTC 2017

Daniel Ford wrote:
>This would be fine as long as my clock has access to the TZdb each year,
>but what if the database someday ceases to exist (or be maintained)?

Then you lose.  DST rules change from year to year; even if you're only
interested in current times you need frequent updates.  In practice the
extent of the need varies between locations, but even in the most stable
cases after a few years you'd just be guessing.

The database does support this kind of guessing, however.  There's a
nearly-POSIX-TZ field in the tzfiles, which represents the current best
guess of what behaviour the zone will have after all the explicitly listed
transitions.  You can extract that field and process it indefinitely on
the small device.


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