[Datetime-SIG] A local timezone class

Alexander Belopolsky alexander.belopolsky at gmail.com
Sat Aug 29 02:26:56 CEST 2015

On Fri, Aug 28, 2015 at 8:06 PM, Guido van Rossum <guido at python.org> wrote:

> ..
> So, again, why have we been shy of adding this to the stdlib? We did
> (eventually) add the fixed offset classes.

I may be wrong, but I thought it was due to unresolvable DST fold issues
that are mooted by PEP 495.  (At least that was the reason I did not push
for LocalTimezone as hard as I did for the fixed offset class.)

I am definitely +1 on having LocalTimezone (or timezone.local) in the
datetime module, but there is one reason why I would rather see it as a
part of a larger Olson TZ database-size offering.

If we just add LocalTimezone, pickling a datetime instance on one system
and reading it on another with a different TZ will result in changing the
time value.

On the other hand, if we have a complete TZ database, then LocalTimezone
can simply become an alias for Zoneinfo(os.environ['TZ']) and there will be
no problem sharing aware datetime objects between systems that use the same
version of the database.
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