datetimetester.py 文件源码

def dst(self, dt):
        if dt is None or dt.tzinfo is None:
            # An exception instead may be sensible here, in one or more of
            # the cases.
            return ZERO
        assert dt.tzinfo is self

        # Find first Sunday in April.
        start = first_sunday_on_or_after(DSTSTART.replace(year=dt.year))
        assert start.weekday() == 6 and start.month == 4 and start.day <= 7

        # Find last Sunday in October.
        end = first_sunday_on_or_after(DSTEND.replace(year=dt.year))
        assert end.weekday() == 6 and end.month == 10 and end.day >= 25

        # Can't compare naive to aware objects, so strip the timezone from
        # dt first.
        if start <= dt.replace(tzinfo=None) < end:
            return HOUR
        else:
            return ZERO