[Python-Dev] datetime +/- scalars (int, long, float)? (original) (raw)

M.-A. Lemburg mal@lemburg.com
Tue, 05 Mar 2002 21:41:31 +0100

Guido van Rossum wrote:

> > [MAL] > > You should forget about DST if you want a sane > > implementation. Same for leap seconds. I think I want to introduce a new concept, closely related to local time, that I'll dub "naive time" for now. In naive time, there is no timezone and there is no DST. To compensate for DST, you have to manually change the clock, which is an action outside the system, unknown to the system, and irrelevant to the working of the system. Ditto to change time zones. Naive time is what you see on your watch or your Palm organizer (apparently not on PocketPC or Windows/CE though, which are timezone aware). A day is always 24 hours, and the clock always shows local time. When the DST jump happens, you lose or win an hour but you do your best to pretend it didn't happen, by going to bed a little earlier or by partying a little longer (or any other activity that causes memory loss :-). My Palm has no problem keeping track of appointments in different timezones: when I have a meeting in San Francisco at 11am, I enter it at 11am, and when I fly there, I move the Palm's clock three hours back. Naive time adapts to local time -- time flies (or stands still) when you're in an airplane crossing timezones. Naive time calculations are easier than local time calculations, because they don't have to worry about DST. You only have to be careful when converting between naive time and UTC (or anything else that has a concept of timezone).

Just to let you know: you are slowly narrowing in on mxDateTime ;-) (the naive type is pretty much what I have implemented as DateTime object).

-- Marc-Andre Lemburg CEO eGenix.com Software GmbH

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