On Tue, Jun 1, 2010 at 10:41 AM, Mark Dickinson <dickinsm@gmail.com> wrote: ..
As per the POSIX standard (IIUC), [datetime(1985, 6, 30, 23, 59, 60)] would be immediately converted to datetime.datetime(1985, 7, 1, 0, 0, 0) internally. So the datetime object itself wouldn't support leap seconds, and would continue to use POSIX time; only the constructor would support leap seconds.
It is my understanding that POSIX mandates that mktime() function normalizes the tm structure and therefore converts (1985, 6, 30, 23, 59, 60, ...) to (1985, 7, 1, 0, 0, 0, ...). It is not quite accurate to say that tm structure is converted "immediately". It is perfectly legal to pass around non-normalized tm structures and have for example utc2gps() function that would produce different values for Y-M-D 23:59:60 and T-M-[D+1] 00:00:00. I would prefer a similar behavior for datetime constructor:
datetime(1985, 6, 30, 23, 59, 60).second 60 datetime(1985, 6, 30, 23, 59, 60).timetuple() (1985, 6, 30, 23, 59, 60, ...)
but
datetime(1985, 6, 30, 23, 59, 60) - datetime(1985, 7, 1, 0, 0, 0) datetime.timedelta(0)