[Python-Dev] Aware datetime from naive local time Was: Status on PEP-431 Timezones

[Alexander Belopolsky]

On Thu, Apr 9, 2015 at 4:51 PM, Isaac Schwabacher <ischwabacher at wisc.edu>
wrote:

> > > > Well, you are right, but at least we do have a localtime utility
> hidden in the email package:
> > > >
> > > > >>> from datetime import *
> > > > >>> from email.utils import localtime
> > > > >>> print(localtime(datetime.now()))
> > > > 2015-04-09 15:19:12.840000-04:00
> > > >
> > > > You can read <http://bugs.python.org/issue9527> for the reasons it
> did not make into datetime.
> > >
> > > But that's restricted to the system time zone. Nothing good ever comes
> from the system time zone...
> >
> > Let's solve one problem at a time. ...
>
> PEP 431 proposes to import zoneinfo into the stdlib, ...


I am changing the subject so that we can focus on one question without
diverting to PEP-size issues that are better suited for python ideas.

I would like to add a functionality to the datetime module that would solve
a seemingly simple problem: given a naive datetime instance assumed to be
in local time, construct the corresponding aware datetime object with
tzinfo set to an appropriate fixed offset datetime.timezone instance.

Python 3 has this functionality implemented in the email package since
version 3.3, and it appears to work well even
in the ambiguous hour

>>> from email.utils import localtime
>>> from datetime import datetime
>>> localtime(datetime(2014,11,2,1,30)).strftime('%c %z %Z')
'Sun Nov  2 01:30:00 2014 -0400 EDT'
>>> localtime(datetime(2014,11,2,1,30), isdst=0).strftime('%c %z %Z')
'Sun Nov  2 01:30:00 2014 -0500 EST'

However, in a location with a more interesting history, you can get a
situation tha
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