app/django/utils/tzinfo.py
author Daniel Bentley <dbentley@google.com>
Wed, 15 Apr 2009 08:01:17 +0000
changeset 2184 a1bda9afa5d0
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Step 2 of moving to new seeding model. Create Seeder class, which abstracts some seeding. Move user to Seeder class, and make new OrganizationSeeder class. If people like this, I'll finish the rest soon. Patch by: Dan Bentley

"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):
        if isinstance(offset, timedelta):
            self.__offset = offset
            offset = self.__offset.seconds // 60
        else:
            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)
        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, ValueError):
            # 32 bit systems can't handle dates after Jan 2038, and certain
            # systems can't handle dates before ~1901-12-01:
            #
            # >>> time.mktime((1900, 1, 13, 0, 0, 0, 0, 0, 0))
            # OverflowError: mktime argument out of range
            # >>> time.mktime((1850, 1, 13, 0, 0, 0, 0, 0, 0))
            # ValueError: year out of range
            #
            # In this case, we fake the date, because we only care about the
            # DST flag.
            tt = (2037,) + tt[1:]
            stamp = time.mktime(tt)
        tt = time.localtime(stamp)
        return tt.tm_isdst > 0