| 1 | from datetime import tzinfo, timedelta, datetime
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| 2 |
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| 3 | ZERO = timedelta(0)
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| 4 | HOUR = timedelta(hours=1)
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| 5 |
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| 6 | # A UTC class.
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| 7 |
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| 8 | class UTC(tzinfo):
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| 9 | """UTC"""
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| 10 |
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| 11 | def utcoffset(self, dt):
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| 12 | return ZERO
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| 13 |
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| 14 | def tzname(self, dt):
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| 15 | return "UTC"
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| 16 |
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| 17 | def dst(self, dt):
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| 18 | return ZERO
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| 19 |
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| 20 | utc = UTC()
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| 21 |
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| 22 | # A class building tzinfo objects for fixed-offset time zones.
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| 23 | # Note that FixedOffset(0, "UTC") is a different way to build a
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| 24 | # UTC tzinfo object.
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| 25 |
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| 26 | class FixedOffset(tzinfo):
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| 27 | """Fixed offset in minutes east from UTC."""
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| 28 |
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| 29 | def __init__(self, offset, name):
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| 30 | self.__offset = timedelta(minutes = offset)
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| 31 | self.__name = name
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| 32 |
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| 33 | def utcoffset(self, dt):
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| 34 | return self.__offset
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| 35 |
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| 36 | def tzname(self, dt):
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| 37 | return self.__name
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| 38 |
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| 39 | def dst(self, dt):
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| 40 | return ZERO
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| 41 |
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| 42 | # A class capturing the platform's idea of local time.
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| 43 |
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| 44 | import time as _time
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| 45 |
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| 46 | STDOFFSET = timedelta(seconds = -_time.timezone)
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| 47 | if _time.daylight:
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| 48 | DSTOFFSET = timedelta(seconds = -_time.altzone)
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| 49 | else:
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| 50 | DSTOFFSET = STDOFFSET
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| 51 |
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| 52 | DSTDIFF = DSTOFFSET - STDOFFSET
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| 53 |
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| 54 | class LocalTimezone(tzinfo):
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| 55 |
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| 56 | def utcoffset(self, dt):
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| 57 | if self._isdst(dt):
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| 58 | return DSTOFFSET
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| 59 | else:
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| 60 | return STDOFFSET
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| 61 |
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| 62 | def dst(self, dt):
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| 63 | if self._isdst(dt):
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| 64 | return DSTDIFF
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| 65 | else:
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| 66 | return ZERO
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| 67 |
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| 68 | def tzname(self, dt):
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| 69 | return _time.tzname[self._isdst(dt)]
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| 70 |
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| 71 | def _isdst(self, dt):
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| 72 | tt = (dt.year, dt.month, dt.day,
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| 73 | dt.hour, dt.minute, dt.second,
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| 74 | dt.weekday(), 0, -1)
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| 75 | stamp = _time.mktime(tt)
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| 76 | tt = _time.localtime(stamp)
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| 77 | return tt.tm_isdst > 0
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| 78 |
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| 79 | Local = LocalTimezone()
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| 80 |
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| 81 |
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| 82 | # A complete implementation of current DST rules for major US time zones.
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| 83 |
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| 84 | def first_sunday_on_or_after(dt):
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| 85 | days_to_go = 6 - dt.weekday()
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| 86 | if days_to_go:
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| 87 | dt += timedelta(days_to_go)
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| 88 | return dt
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| 89 |
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| 90 | # In the US, DST starts at 2am (standard time) on the first Sunday in April.
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| 91 | DSTSTART = datetime(1, 4, 1, 2)
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| 92 | # and ends at 2am (DST time; 1am standard time) on the last Sunday of Oct.
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| 93 | # which is the first Sunday on or after Oct 25.
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| 94 | DSTEND = datetime(1, 10, 25, 1)
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| 95 |
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| 96 | class USTimeZone(tzinfo):
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| 97 |
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| 98 | def __init__(self, hours, reprname, stdname, dstname):
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| 99 | self.stdoffset = timedelta(hours=hours)
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| 100 | self.reprname = reprname
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| 101 | self.stdname = stdname
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| 102 | self.dstname = dstname
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| 103 |
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| 104 | def __repr__(self):
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| 105 | return self.reprname
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| 106 |
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| 107 | def tzname(self, dt):
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| 108 | if self.dst(dt):
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| 109 | return self.dstname
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| 110 | else:
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| 111 | return self.stdname
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| 112 |
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| 113 | def utcoffset(self, dt):
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| 114 | return self.stdoffset + self.dst(dt)
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| 115 |
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| 116 | def dst(self, dt):
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| 117 | if dt is None or dt.tzinfo is None:
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| 118 | # An exception may be sensible here, in one or both cases.
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| 119 | # It depends on how you want to treat them. The default
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| 120 | # fromutc() implementation (called by the default astimezone()
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| 121 | # implementation) passes a datetime with dt.tzinfo is self.
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| 122 | return ZERO
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| 123 | assert dt.tzinfo is self
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| 124 |
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| 125 | # Find first Sunday in April & the last in October.
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| 126 | start = first_sunday_on_or_after(DSTSTART.replace(year=dt.year))
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| 127 | end = first_sunday_on_or_after(DSTEND.replace(year=dt.year))
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| 128 |
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| 129 | # Can't compare naive to aware objects, so strip the timezone from
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| 130 | # dt first.
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| 131 | if start <= dt.replace(tzinfo=None) < end:
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| 132 | return HOUR
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| 133 | else:
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| 134 | return ZERO
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| 135 |
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| 136 | Eastern = USTimeZone(-5, "Eastern", "EST", "EDT")
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| 137 | Central = USTimeZone(-6, "Central", "CST", "CDT")
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| 138 | Mountain = USTimeZone(-7, "Mountain", "MST", "MDT")
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| 139 | Pacific = USTimeZone(-8, "Pacific", "PST", "PDT")
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