On 2022-04-17 10:15:54 +0200, Peter J. Holzer wrote: > On 2022-04-17 06:08:54 +1000, Chris Angelico wrote: > > On Sun, 17 Apr 2022 at 03:37, Peter J. Holzer <hjp-pyt...@hjp.at> wrote: > > > Therefore a new class (provisionally called timedeltacal, because it is > > > calendaric, not absolute) should be added to datetime: > > > > > > Internally it stores months, days, seconds and microseconds as ints. > > > > > > The seconds and microseconds split is mostly for compatibility with > > > datetime and timedelta. We could store seconds as a float instead. > > > > > > We don't store minutes since leap seconds aren't usually represented in > > > "computer time", so they are unlikely to be useful in a timedeltacal > > > object. > > > > > > Days are stored since they aren't a fixed multiple of any smaller unit. > > > Months are stored since they aren't a fixed multiple of any smaller unit. > > > > > > Hours, weeks and years aren't stored since they are always 60 minutes, 7 > > > days and 12 months respectively. > > > > It sounds like you're planning for annual DST changes, but what about > > other shifts? What about when a location adopts standard time, which > > could change their UTC offset (yes, I'm aware that most places adopted > > standard time before UTC was a thing, but we still usually call it a > > UTC offset rather than messing with GMT-UTC changeover) by an > > arbitrary amount, even minutes? > > Yes, I think you are right. I first thought it wouldn't matter because > you'd have to look it up in the database anyway, but that's a > non-sequitur. Clearly, when you cities switched from local times to > timezones, one hour had to be longer or shorter than 3600 seconds. > Similarily if India decided to switch to a whole-hour offset, then they > would have one hour of 30 or 90 minutes.
Thinking about it some more (while writing test cases) I've changed my
mind again. I think "1 hour" should always be 3600 seconds (disregarding
leap seconds), not "the time until the hour hand has advanced by 30° and
the minute hand is in the same position". If I sit at a bar at 00:30 on
the last Sunday in March, and I continue to sit there for 2 hours, then
it's 03:30 when I get out of the bar, not 02:30. 02:30 doesn't even
exist.
That might be considered an inconsistency, but I think it "does the
right thing" in most cases.
hp
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| | | h...@hjp.at | -- Charles Stross, "Creative writing
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