[New-bugs-announce] [issue23600] tizinfo.fromutc changed for tzinfo wih StdOffset=0, DstOffset=1

[Peter J C Law]

New submission from Peter J C Law:

There's a difference in behaviour between the ``fromutc`` method on a tzinfo between Python 2 and Python 3, though only under the specific case of Summer Time in regions whose usual offset is 0.

>From what I can tell, it's the Python 3 one which is wrong, based on it no longer matching the sample implementation provided in the docs and on it appearing to report the wrong times for ``datetime.now(tz)`` when on a machine configured for BST during June 2015.
Similar results can also be achieved using a manually constructed ``datetime`` for dates during summer 2014.

I've put the python script (and sample outputs) I used to investigate in a gist at https://gist.github.com/PeterJCLaw/d8bcc168d68acf066811#file-time_issues-py. The outputs there are for pythons 2.7.9 and 3.4.0.

----------
components: Library (Lib)
messages: 237407
nosy: peterjclaw
priority: normal
severity: normal
status: open
title: tizinfo.fromutc changed for tzinfo wih StdOffset=0, DstOffset=1
type: behavior
versions: Python 3.4

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue23600>
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