from datetime import tzinfo, timedelta, datetime ZERO = timedelta(0)HOUR = timedelta(hours=1) # A UTC class. class UTC(tzinfo):    """UTC"""     def utcoffset(self, dt):        return ZERO     def tzname(self, dt):        return "UTC"     def dst(self, dt):        return ZERO utc = UTC() # A class building tzinfo objects for fixed-offset time zones.# Note that FixedOffset(0, "UTC") is a different way to build a# UTC tzinfo object. class FixedOffset(tzinfo):    """Fixed offset in minutes east from UTC."""     def __init__(self, offset, name):        self.__offset = timedelta(minutes = offset)        self.__name = name     def utcoffset(self, dt):        return self.__offset     def tzname(self, dt):        return self.__name     def dst(self, dt):        return ZERO # A class capturing the platform's idea of local time. import time as _time STDOFFSET = timedelta(seconds = -_time.timezone)if _time.daylight:    DSTOFFSET = timedelta(seconds = -_time.altzone)else:    DSTOFFSET = STDOFFSET DSTDIFF = DSTOFFSET - STDOFFSET class LocalTimezone(tzinfo):     def utcoffset(self, dt):        if self._isdst(dt):            return DSTOFFSET        else:            return STDOFFSET     def dst(self, dt):        if self._isdst(dt):            return DSTDIFF        else:            return ZERO     def tzname(self, dt):        return _time.tzname[self._isdst(dt)]     def _isdst(self, dt):        tt = (dt.year, dt.month, dt.day,              dt.hour, dt.minute, dt.second,              dt.weekday(), 0, -1)        stamp = _time.mktime(tt)        tt = _time.localtime(stamp)        return tt.tm_isdst > 0 Local = LocalTimezone()  # A complete implementation of current DST rules for major US time zones. def first_sunday_on_or_after(dt):    days_to_go = 6 - dt.weekday()    if days_to_go:        dt += timedelta(days_to_go)    return dt # In the US, DST starts at 2am (standard time) on the first Sunday in April.DSTSTART = datetime(1, 4, 1, 2)# and ends at 2am (DST time; 1am standard time) on the last Sunday of Oct.# which is the first Sunday on or after Oct 25.DSTEND = datetime(1, 10, 25, 1) class USTimeZone(tzinfo):     def __init__(self, hours, reprname, stdname, dstname):        self.stdoffset = timedelta(hours=hours)        self.reprname = reprname        self.stdname = stdname        self.dstname = dstname     def __repr__(self):        return self.reprname     def tzname(self, dt):        if self.dst(dt):            return self.dstname        else:            return self.stdname     def utcoffset(self, dt):        return self.stdoffset + self.dst(dt)     def dst(self, dt):        if dt is None or dt.tzinfo is None:            # An exception may be sensible here, in one or both cases.            # It depends on how you want to treat them.  The default            # fromutc() implementation (called by the default astimezone()            # implementation) passes a datetime with dt.tzinfo is self.            return ZERO        assert dt.tzinfo is self         # Find first Sunday in April & the last in October.        start = first_sunday_on_or_after(DSTSTART.replace(year=dt.year))        end = first_sunday_on_or_after(DSTEND.replace(year=dt.year))         # 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 Eastern  = USTimeZone(-5, "Eastern",  "EST", "EDT")Central  = USTimeZone(-6, "Central",  "CST", "CDT")Mountain = USTimeZone(-7, "Mountain", "MST", "MDT")Pacific  = USTimeZone(-8, "Pacific",  "PST", "PDT")