diff options
Diffstat (limited to 'Doc/includes')
| -rw-r--r-- | Doc/includes/tzinfo-examples.py | 130 |
1 files changed, 68 insertions, 62 deletions
diff --git a/Doc/includes/tzinfo-examples.py b/Doc/includes/tzinfo-examples.py index 3a8cf47..ae5a509 100644 --- a/Doc/includes/tzinfo-examples.py +++ b/Doc/includes/tzinfo-examples.py @@ -1,46 +1,13 @@ -from datetime import tzinfo, timedelta, datetime +from datetime import tzinfo, timedelta, datetime, timezone 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 +SECOND = timedelta(seconds=1) # A class capturing the platform's idea of local time. - +# (May result in wrong values on historical times in +# timezones where UTC offset and/or the DST rules had +# changed in the past.) import time as _time STDOFFSET = timedelta(seconds = -_time.timezone) @@ -53,6 +20,16 @@ DSTDIFF = DSTOFFSET - STDOFFSET class LocalTimezone(tzinfo): + def fromutc(self, dt): + assert dt.tzinfo is self + stamp = (dt - datetime(1970, 1, 1, tzinfo=self)) // SECOND + args = _time.localtime(stamp)[:6] + dst_diff = DSTDIFF // SECOND + # Detect fold + fold = (args == _time.localtime(stamp - dst_diff)) + return datetime(*args, microsecond=dt.microsecond, + tzinfo=self, fold=fold) + def utcoffset(self, dt): if self._isdst(dt): return DSTOFFSET @@ -99,20 +76,37 @@ def first_sunday_on_or_after(dt): # 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) +# and ends at 2am (DST time) on the first Sunday of Nov. +DSTEND_2007 = datetime(1, 11, 1, 2) # 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 in April and to end at 2am (DST 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) +DSTEND_1987_2006 = datetime(1, 10, 25, 2) # 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 +# Sunday in April (the one on or after April 24) and to end at 2am (DST 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 +def us_dst_range(year): + # Find start and end times for US DST. For years before 1967, return + # start = end for no DST. + if 2006 < year: + dststart, dstend = DSTSTART_2007, DSTEND_2007 + elif 1986 < year < 2007: + dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006 + elif 1966 < year < 1987: + dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986 + else: + return (datetime(year, 1, 1), ) * 2 + + start = first_sunday_on_or_after(dststart.replace(year=year)) + end = first_sunday_on_or_after(dstend.replace(year=year)) + return start, end + + class USTimeZone(tzinfo): def __init__(self, hours, reprname, stdname, dstname): @@ -141,27 +135,39 @@ class USTimeZone(tzinfo): # 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)) - + start, end = us_dst_range(dt.year) # Can't compare naive to aware objects, so strip the timezone from # dt first. - if start <= dt.replace(tzinfo=None) < end: + dt = dt.replace(tzinfo=None) + if start + HOUR <= dt < end - HOUR: + # DST is in effect. return HOUR - else: - return ZERO + if end - HOUR <= dt < end: + # Fold (an ambiguous hour): use dt.fold to disambiguate. + return ZERO if dt.fold else HOUR + if start <= dt < start + HOUR: + # Gap (a non-existent hour): reverse the fold rule. + return HOUR if dt.fold else ZERO + # DST is off. + return ZERO + + def fromutc(self, dt): + assert dt.tzinfo is self + start, end = us_dst_range(dt.year) + start = start.replace(tzinfo=self) + end = end.replace(tzinfo=self) + std_time = dt + self.stdoffset + dst_time = std_time + HOUR + if end <= dst_time < end + HOUR: + # Repeated hour + return std_time.replace(fold=1) + if std_time < start or dst_time >= end: + # Standard time + return std_time + if start <= std_time < end - HOUR: + # Daylight saving time + return dst_time + Eastern = USTimeZone(-5, "Eastern", "EST", "EDT") Central = USTimeZone(-6, "Central", "CST", "CDT") |