/Doc/includes/tzinfo-examples.py
http://unladen-swallow.googlecode.com/ · Python · 169 lines · 97 code · 38 blank · 34 comment · 17 complexity · 94356334411344df7806bb35f7ea1062 MD5 · raw file
- 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
- # US DST Rules
- #
- # This is a simplified (i.e., wrong for a few cases) set of rules for US
- # DST start and end times. For a complete and up-to-date set of DST rules
- # and timezone definitions, visit the Olson Database (or try pytz):
- # http://www.twinsun.com/tz/tz-link.htm
- # http://sourceforge.net/projects/pytz/ (might not be up-to-date)
- #
- # In the US, since 2007, DST starts at 2am (standard time) on the second
- # Sunday in March, which is the first Sunday on or after Mar 8.
- DSTSTART_2007 = datetime(1, 3, 8, 2)
- # and ends at 2am (DST time; 1am standard time) on the first Sunday of Nov.
- DSTEND_2007 = datetime(1, 11, 1, 1)
- # From 1987 to 2006, DST used to start at 2am (standard time) on the first
- # Sunday in April and to end at 2am (DST time; 1am standard time) on the last
- # Sunday of October, which is the first Sunday on or after Oct 25.
- DSTSTART_1987_2006 = datetime(1, 4, 1, 2)
- DSTEND_1987_2006 = datetime(1, 10, 25, 1)
- # From 1967 to 1986, DST used to start at 2am (standard time) on the last
- # Sunday in April (the one on or after April 24) and to end at 2am (DST time;
- # 1am standard time) on the last Sunday of October, which is the first Sunday
- # on or after Oct 25.
- DSTSTART_1967_1986 = datetime(1, 4, 24, 2)
- DSTEND_1967_1986 = DSTEND_1987_2006
- 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 start and end times for US DST. For years before 1967, return
- # ZERO for no DST.
- if 2006 < dt.year:
- dststart, dstend = DSTSTART_2007, DSTEND_2007
- elif 1986 < dt.year < 2007:
- dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006
- elif 1966 < dt.year < 1987:
- dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986
- else:
- return ZERO
- 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")