django/utils/tzinfo.py

   1 "Implementation of tzinfo classes for use with datetime.datetime."
   2
   3 import locale
   4 import time
   5 from datetime import timedelta, tzinfo
   6 from django.utils.encoding import smart_unicode
   7
   8 try:
   9     DEFAULT_ENCODING = locale.getdefaultlocale()[1] or 'ascii'
  10 except:
  11     # Any problems at all determining the locale and we fallback. See #5846.
  12     DEFAULT_ENCODING = 'ascii'
  13
  14 class FixedOffset(tzinfo):
  15     "Fixed offset in minutes east from UTC."
  16     def __init__(self, offset):
  17         self.__offset = timedelta(minutes=offset)
  18         self.__name = u"%+03d%02d" % (offset // 60, offset % 60)
  19
  20     def __repr__(self):
  21         return self.__name
  22
  23     def utcoffset(self, dt):
  24         return self.__offset
  25
  26     def tzname(self, dt):
  27         return self.__name
  28
  29     def dst(self, dt):
  30         return timedelta(0)
  31
  32 class LocalTimezone(tzinfo):
  33     "Proxy timezone information from time module."
  34     def __init__(self, dt):
  35         tzinfo.__init__(self, dt)
  36         self._tzname = self.tzname(dt)
  37
  38     def __repr__(self):
  39         return self._tzname
  40
  41     def utcoffset(self, dt):
  42         if self._isdst(dt):
  43             return timedelta(seconds=-time.altzone)
  44         else:
  45             return timedelta(seconds=-time.timezone)
  46
  47     def dst(self, dt):
  48         if self._isdst(dt):
  49             return timedelta(seconds=-time.altzone) - timedelta(seconds=-time.timezone)
  50         else:
  51             return timedelta(0)
  52
  53     def tzname(self, dt):
  54         try:
  55             return smart_unicode(time.tzname[self._isdst(dt)], DEFAULT_ENCODING)
  56         except UnicodeDecodeError:
  57             return None
  58
  59     def _isdst(self, dt):
  60         tt = (dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second, dt.weekday(), 0, -1)
  61         try:
  62             stamp = time.mktime(tt)
  63         except OverflowError:
  64             # 32 bit systems can't handle dates after Jan 2038, so we fake it
  65             # in that case (since we only care about the DST flag here).
  66             tt = (2037,) + tt[1:]
  67             stamp = time.mktime(tt)
  68         tt = time.localtime(stamp)
  69         return tt.tm_isdst > 0