[issue38051] time.strftime handling %z/%Z badly

[John Daily]

New submission from John Daily <pybugs at yoggi.33mail.com>:

My apologies if this is a duplicate; there are more than a few bug reports on time and strftime, but I wasn't able to locate any reporting this specifically.

I'd be happy to do more in-depth tests with some guidance. I see that this is largely the responsibility of system libraries, but it seems likely that Python is doing something incorrectly when invoking them since the behavior is broken in both Mac and Windows.

On both my personal Mac laptop and work Windows laptop, time.strftime('%z') gives the wrong output. On Windows, '%Z' also fails.

I'm currently at -0400 (EDT) and my best guess is that because the tm_isdst flag is set to false, it's interpreting my Eastern time zone as it would be when we're no longer on DST.

Technically displaying "UTC" is also a bug, since the actual time zone is "GMT". Python 3.6 on my Amazon Linux instance handles everything correctly.


Mac, 3.7.3:

>>> epoch = int(datetime.datetime.now().timestamp())
>>> epoch
1567872682
>>> gmt = time.gmtime(epoch)
>>> gmt.tm_zone
'UTC'
>>> time.strftime('%Z', gmt)
'UTC'
>>> time.strftime('%z', gmt)
'-0500'

Python 3.7.1, Windows 7

>>> gmt.tm_zone
'UTC'
>>> time.strftime('%Z', gmt)
'Eastern Standard Time'
>>> time.strftime('%z', gmt)
'-0500'

Python 3.6.8, Amazon Linux

>>> epoch = int(datetime.datetime.now().timestamp())
>>> gmt = time.gmtime(epoch)
>>> gmt.tm_zone
'GMT'
>>> time.strftime('%Z', gmt)
'GMT'
>>> time.strftime('%z', gmt)
'+0000'

----------
messages: 351306
nosy: macintux
priority: normal
severity: normal
status: open
title: time.strftime handling %z/%Z badly
versions: Python 3.7

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<https://bugs.python.org/issue38051>
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