Issue 13277: tzinfo subclasses information (original) (raw)

Issue13277

Created on 2011-10-27 16:40 by orsenthil, last changed 2022-04-11 14:57 by admin.

Messages (3)
msg146501 - (view)	Author: Senthil Kumaran (orsenthil) *	Date: 2011-10-27 16:40
This was in the docs mailing list, not translated to bug report Paul Koning wrote: Section 8.1.6 of the library manual talks about utcoffset(dt)-dst(dt) as the "standard offset" and says that this should not depend on the date or +time but only on the location. This is not true as there cases were certain locations changed the time offsets as per their convenience. It is either a doc fix to remove that sentence if the datetime.astimezone does not depend upon utcoffset(dt)-dst(dt), or if it does, then it is a code fix.
msg221767 - (view)	Author: Mark Lawrence (BreamoreBoy) *	Date: 2014-06-28 02:05
I don't understand the implications of timezone stuff at all so can a guru on the subject please comment on this.
msg221769 - (view)	Author: Alexander Belopolsky (belopolsky) *	Date: 2014-06-28 02:26
I would say this is a doc issue. There are some tzinfo algorithms that depend on utcoffset(dt)-dst(dt) being invariant, but this is the part of datetime library that I have never fully understood. What I do understand is that conversion from local time to UTC or another timezone is a hard and not always solvable problem (some local times are invalid and some are ambiguous). (If some local government decides that 00:59 should be followed by 02:00, one is hard pressed to figure out what 01:30 local time is in UTC.) I think documentation should emphasize the fact that the standard library only supports fixed offset timezones. It is up to the application programmer or a 3rd party library to figure out which fixed offset is appropriate in which case.