Bugs item #1647654, was opened at 2007-01-30 06:48
Message generated for change (Comment added) made by pboddie
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1647654&group_id=5470
Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: James Henstridge (jhenstridge)
Assigned to: Nobody/Anonymous (nobody)
Summary: No obvious and correct way to get the time zone offset
Initial Comment:
It would be nice if the Python time module provided an obvious way to get the
local time UTC offset for an arbitrary time stamp. The existing constants
included in the module are not sufficient to correctly determine this value.
As context, the Bazaar version control system (written in Python), the local
time UTC offset is recorded in a commit.
The method used in releases prior to 0.14 made use of the "daylight",
"timezone" and "altzone" constants from the time module like this:
if time.localtime(t).tm_isdst and time.daylight:
return -time.altzone
else:
return -time.timezone
This worked most of the time, but would occasionally give incorrect results.
On Linux, the local time system can handle different daylight saving rules for
different spans of years. For years where the rules change, these constants
can provide incorrect data. Furthermore, they may be incorrect for time stamps
in the past.
I personally ran into this problem last December when Western Australia adopted
daylight saving -- time.altzone gave an incorrect value until the start of 2007.
Having a function in the standard library to calculate this offset would solve
the problem. The implementation we ended up with for Bazaar was:
offset = datetime.fromtimestamp(t) - datetime.utcfromtimestamp(t)
return offset.days * 86400 + offset.seconds
Another alternative would be to expose tm_gmtoff on time tuples (perhaps using
the above code to synthesise it on platforms that don't have the field).
----------------------------------------------------------------------
Comment By: Paul Boddie (pboddie)
Date: 2007-02-24 01:31
Message:
Logged In: YES
user_id=226443
Originator: NO
See patch #1667546 for a time module function returning extended time
tuples. The datetime-based solution you provide is quite a clever
workaround using "naive" datetime objects, but I'm inclined to think that
some more convenient way of getting "aware" datetime objects would be
nicer.
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1647654&group_id=5470
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
