app/django/utils/tzinfo.py
author Todd Larsen <tlarsen@google.com>
Wed, 20 Aug 2008 00:10:59 +0000
changeset 88 9a8180f0941a
parent 54 03e267d67478
child 323 ff1a9aa48cfd
permissions -rw-r--r--
Some additional __doc__ comments (with some ideas for future plans) and removal of some unnecessary imports.

"Implementation of tzinfo classes for use with datetime.datetime."

import locale
import time
from datetime import timedelta, tzinfo
from django.utils.encoding import smart_unicode

try:
    DEFAULT_ENCODING = locale.getdefaultlocale()[1] or 'ascii'
except:
    # Any problems at all determining the locale and we fallback. See #5846.
    DEFAULT_ENCODING = 'ascii'

class FixedOffset(tzinfo):
    "Fixed offset in minutes east from UTC."
    def __init__(self, offset):
        self.__offset = timedelta(minutes=offset)
        self.__name = u"%+03d%02d" % (offset // 60, offset % 60)

    def __repr__(self):
        return self.__name

    def utcoffset(self, dt):
        return self.__offset

    def tzname(self, dt):
        return self.__name

    def dst(self, dt):
        return timedelta(0)

class LocalTimezone(tzinfo):
    "Proxy timezone information from time module."
    def __init__(self, dt):
        tzinfo.__init__(self, dt)
        self._tzname = self.tzname(dt)

    def __repr__(self):
        return self._tzname

    def utcoffset(self, dt):
        if self._isdst(dt):
            return timedelta(seconds=-time.altzone)
        else:
            return timedelta(seconds=-time.timezone)

    def dst(self, dt):
        if self._isdst(dt):
            return timedelta(seconds=-time.altzone) - timedelta(seconds=-time.timezone)
        else:
            return timedelta(0)

    def tzname(self, dt):
        try:
            return smart_unicode(time.tzname[self._isdst(dt)], DEFAULT_ENCODING)
        except UnicodeDecodeError:
            return None

    def _isdst(self, dt):
        tt = (dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second, dt.weekday(), 0, -1)
        try:
            stamp = time.mktime(tt)
        except OverflowError:
            # 32 bit systems can't handle dates after Jan 2038, so we fake it
            # in that case (since we only care about the DST flag here).
            tt = (2037,) + tt[1:]
            stamp = time.mktime(tt)
        tt = time.localtime(stamp)
        return tt.tm_isdst > 0