Re: [Datetime-SIG] Calendar vs timespan calculations...
Sorry this is old, but: Chris Barker chris.barker at noaa.gov:
[that a day is always 24 hours] it's not an assumption, it's a definition.
Right, but that's like defining Pi to be three. It's not in accordance to reality, and therefore it causes a lot of problems.
No it's not -- not at all. "day" has two definitions, one is 24 hours, and one is incrementing the date on a calendar (or something like that). Both definitions are equally valid, we jsut need to be clear about which one we are using. period. what I suppose is less clear is which definition is being used by the timedetla object. I argue that the 24 hr definition is what is used there, because, well, that's exactly how it is used internally: In [3]: datetime.timedelta(days=1) Out[3]: datetime.timedelta(1) In [4]: datetime.timedelta(seconds=24*60*60) Out[4]: datetime.timedelta(1) Perhaps the original intent was that "days" means calendar days, and for naive datetimes, it turns out to be the same thing, but that is not what the implementation does, and given that it supports seconds and microseconds, but not months or years, the API is pretty clearly designed for timespans, not calendar definitions. But maybe this will all get cleared up with the Glossary Recently posted. -CHB -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov
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Chris Barker