# Django 2.2.9.dev20191202104323 文档

# pytz 源代码

    '''
    datetime.tzinfo timezone definitions generated from the
    Olson timezone database:

        ftp://elsie.nci.nih.gov/pub/tz*.tar.gz

    See the datetime section of the Python Library Reference for information
    on how to use these modules.
    '''

    # The IANA (nee Olson) database is updated several times a year.
    OLSON_VERSION = '2017b'
    VERSION = '2017.2'  # Switching to pip compatible version numbering.
    __version__ = VERSION

    OLSEN_VERSION = OLSON_VERSION # Old releases had this misspelling

    __all__ = [
        'timezone', 'utc', 'country_timezones', 'country_names',
        'AmbiguousTimeError', 'InvalidTimeError',
        'NonExistentTimeError', 'UnknownTimeZoneError',
        'all_timezones', 'all_timezones_set',
        'common_timezones', 'common_timezones_set',
        ]

    import sys, datetime, os.path, gettext

    from pytz.exceptions import AmbiguousTimeError
    from pytz.exceptions import InvalidTimeError
    from pytz.exceptions import NonExistentTimeError
    from pytz.exceptions import UnknownTimeZoneError
    from pytz.lazy import LazyDict, LazyList, LazySet
    from pytz.tzinfo import unpickler
    from pytz.tzfile import build_tzinfo, _byte_string

    try:
        unicode

    except NameError: # Python 3.x

        # Python 3.x doesn't have unicode(), making writing code
        # for Python 2.3 and Python 3.x a pain.
        unicode = str

        def ascii(s):
            r"""
            >>> ascii('Hello')
            'Hello'
            >>> ascii('\N{TRADE MARK SIGN}') #doctest: +IGNORE_EXCEPTION_DETAIL
            Traceback (most recent call last):
                ...
            UnicodeEncodeError: ...
            """
            s.encode('ASCII') # Raise an exception if not ASCII
            return s # But return the original string - not a byte string.

    else: # Python 2.x

        def ascii(s):
            r"""
            >>> ascii('Hello')
            'Hello'
            >>> ascii(u'Hello')
            'Hello'
            >>> ascii(u'\N{TRADE MARK SIGN}') #doctest: +IGNORE_EXCEPTION_DETAIL
            Traceback (most recent call last):
                ...
            UnicodeEncodeError: ...
            """
            return s.encode('ASCII')

    def open_resource(name):
        """Open a resource from the zoneinfo subdir for reading.

        Uses the pkg_resources module if available and no standard file
        found at the calculated location.
        """
        name_parts = name.lstrip('/').split('/')
        for part in name_parts:
            if part == os.path.pardir or os.path.sep in part:
                raise ValueError('Bad path segment: %r' % part)
        filename = os.path.join(os.path.dirname(__file__),
                                'zoneinfo', *name_parts)
        if not os.path.exists(filename):
            # http://bugs.launchpad.net/bugs/383171 - we avoid using this
            # unless absolutely necessary to help when a broken version of
            # pkg_resources is installed.
            try:
                from pkg_resources import resource_stream
            except ImportError:
                resource_stream = None

            if resource_stream is not None:
                return resource_stream(__name__, 'zoneinfo/' + name)
        return open(filename, 'rb')

    def resource_exists(name):
        """Return true if the given resource exists"""
        try:
            open_resource(name).close()
            return True
        except IOError:
            return False

    # Enable this when we get some translations?
    # We want an i18n API that is useful to programs using Python's gettext
    # module, as well as the Zope3 i18n package. Perhaps we should just provide
    # the POT file and translations, and leave it up to callers to make use
    # of them.
    #
    # t = gettext.translation(
    #         'pytz', os.path.join(os.path.dirname(__file__), 'locales'),
    #         fallback=True
    #         )
    # def _(timezone_name):
    #     """Translate a timezone name using the current locale, returning Unicode"""
    #     return t.ugettext(timezone_name)

    _tzinfo_cache = {}

    def timezone(zone):
        r''' Return a datetime.tzinfo implementation for the given timezone

        >>> from datetime import datetime, timedelta
        >>> utc = timezone('UTC')
        >>> eastern = timezone('US/Eastern')
        >>> eastern.zone
        'US/Eastern'
        >>> timezone(unicode('US/Eastern')) is eastern
        True
        >>> utc_dt = datetime(2002, 10, 27, 6, 0, 0, tzinfo=utc)
        >>> loc_dt = utc_dt.astimezone(eastern)
        >>> fmt = '%Y-%m-%d %H:%M:%S %Z (%z)'
        >>> loc_dt.strftime(fmt)
        '2002-10-27 01:00:00 EST (-0500)'
        >>> (loc_dt - timedelta(minutes=10)).strftime(fmt)
        '2002-10-27 00:50:00 EST (-0500)'
        >>> eastern.normalize(loc_dt - timedelta(minutes=10)).strftime(fmt)
        '2002-10-27 01:50:00 EDT (-0400)'
        >>> (loc_dt + timedelta(minutes=10)).strftime(fmt)
        '2002-10-27 01:10:00 EST (-0500)'

        Raises UnknownTimeZoneError if passed an unknown zone.

        >>> try:
        ...     timezone('Asia/Shangri-La')
        ... except UnknownTimeZoneError:
        ...     print('Unknown')
        Unknown

        >>> try:
        ...     timezone(unicode('\N{TRADE MARK SIGN}'))
        ... except UnknownTimeZoneError:
        ...     print('Unknown')
        Unknown

        '''
        if zone.upper() == 'UTC':
            return utc

        try:
            zone = ascii(zone)
        except UnicodeEncodeError:
            # All valid timezones are ASCII
            raise UnknownTimeZoneError(zone)

        zone = _unmunge_zone(zone)
        if zone not in _tzinfo_cache:
            if zone in all_timezones_set:
                fp = open_resource(zone)
                try:
                    _tzinfo_cache[zone] = build_tzinfo(zone, fp)
                finally:
                    fp.close()
            else:
                raise UnknownTimeZoneError(zone)

        return _tzinfo_cache[zone]

    def _unmunge_zone(zone):
        """Undo the time zone name munging done by older versions of pytz."""
        return zone.replace('_plus_', '+').replace('_minus_', '-')

    ZERO = datetime.timedelta(0)
    HOUR = datetime.timedelta(hours=1)

    class UTC(datetime.tzinfo):
        """UTC

        Optimized UTC implementation. It unpickles using the single module global
        instance defined beneath this class declaration.
        """
        zone = "UTC"

        _utcoffset = ZERO
        _dst = ZERO
        _tzname = zone

        def fromutc(self, dt):
            if dt.tzinfo is None:
                return self.localize(dt)
            return super(utc.__class__, self).fromutc(dt)

        def utcoffset(self, dt):
            return ZERO

        def tzname(self, dt):
            return "UTC"

        def dst(self, dt):
            return ZERO

        def __reduce__(self):
            return _UTC, ()

        def localize(self, dt, is_dst=False):
            '''Convert naive time to local time'''
            if dt.tzinfo is not None:
                raise ValueError('Not naive datetime (tzinfo is already set)')
            return dt.replace(tzinfo=self)

        def normalize(self, dt, is_dst=False):
            '''Correct the timezone information on the given datetime'''
            if dt.tzinfo is self:
                return dt
            if dt.tzinfo is None:
                raise ValueError('Naive time - no tzinfo set')
            return dt.astimezone(self)

        def __repr__(self):
            return "<UTC>"

        def __str__(self):
            return "UTC"

    UTC = utc = UTC()  # UTC is a singleton

    def _UTC():
        """Factory function for utc unpickling.

        Makes sure that unpickling a utc instance always returns the same
        module global.

        These examples belong in the UTC class above, but it is obscured; or in
        the README.txt, but we are not depending on Python 2.4 so integrating
        the README.txt examples with the unit tests is not trivial.

        >>> import datetime, pickle
        >>> dt = datetime.datetime(2005, 3, 1, 14, 13, 21, tzinfo=utc)
        >>> naive = dt.replace(tzinfo=None)
        >>> p = pickle.dumps(dt, 1)
        >>> naive_p = pickle.dumps(naive, 1)
        >>> len(p) - len(naive_p)
        17
        >>> new = pickle.loads(p)
        >>> new == dt
        True
        >>> new is dt
        False
        >>> new.tzinfo is dt.tzinfo
        True
        >>> utc is UTC is timezone('UTC')
        True
        >>> utc is timezone('GMT')
        False
        """
        return utc
    _UTC.__safe_for_unpickling__ = True

    def _p(*args):
        """Factory function for unpickling pytz tzinfo instances.

        Just a wrapper around tzinfo.unpickler to save a few bytes in each pickle
        by shortening the path.
        """
        return unpickler(*args)
    _p.__safe_for_unpickling__ = True

    class _CountryTimezoneDict(LazyDict):
        """Map ISO 3166 country code to a list of timezone names commonly used
        in that country.

        iso3166_code is the two letter code used to identify the country.

        >>> def print_list(list_of_strings):
        ...     'We use a helper so doctests work under Python 2.3 -> 3.x'
        ...     for s in list_of_strings:
        ...         print(s)

        >>> print_list(country_timezones['nz'])
        Pacific/Auckland
        Pacific/Chatham
        >>> print_list(country_timezones['ch'])
        Europe/Zurich
        >>> print_list(country_timezones['CH'])
        Europe/Zurich
        >>> print_list(country_timezones[unicode('ch')])
        Europe/Zurich
        >>> print_list(country_timezones['XXX'])
        Traceback (most recent call last):
        ...
        KeyError: 'XXX'

        Previously, this information was exposed as a function rather than a
        dictionary. This is still supported::

        >>> print_list(country_timezones('nz'))
        Pacific/Auckland
        Pacific/Chatham
        """
        def __call__(self, iso3166_code):
            """Backwards compatibility."""
            return self[iso3166_code]

        def _fill(self):
            data = {}
            zone_tab = open_resource('zone.tab')
            try:
                for line in zone_tab:
                    line = line.decode('UTF-8')
                    if line.startswith('#'):
                        continue
                    code, coordinates, zone = line.split(None, 4)[:3]
                    if zone not in all_timezones_set:
                        continue
                    try:
                        data[code].append(zone)
                    except KeyError:
                        data[code] = [zone]
                self.data = data
            finally:
                zone_tab.close()

    country_timezones = _CountryTimezoneDict()

    class _CountryNameDict(LazyDict):
        '''Dictionary proving ISO3166 code -> English name.

        >>> print(country_names['au'])
        Australia
        '''
        def _fill(self):
            data = {}
            zone_tab = open_resource('iso3166.tab')
            try:
                for line in zone_tab.readlines():
                    line = line.decode('UTF-8')
                    if line.startswith('#'):
                        continue
                    code, name = line.split(None, 1)
                    data[code] = name.strip()
                self.data = data
            finally:
                zone_tab.close()

    country_names = _CountryNameDict()

    # Time-zone info based solely on fixed offsets

    class _FixedOffset(datetime.tzinfo):

        zone = None # to match the standard pytz API

        def __init__(self, minutes):
            if abs(minutes) >= 1440:
                raise ValueError("absolute offset is too large", minutes)
            self._minutes = minutes
            self._offset = datetime.timedelta(minutes=minutes)

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

        def __reduce__(self):
            return FixedOffset, (self._minutes, )

        def dst(self, dt):
            return ZERO

        def tzname(self, dt):
            return None

        def __repr__(self):
            return 'pytz.FixedOffset(%d)' % self._minutes

        def localize(self, dt, is_dst=False):
            '''Convert naive time to local time'''
            if dt.tzinfo is not None:
                raise ValueError('Not naive datetime (tzinfo is already set)')
            return dt.replace(tzinfo=self)

        def normalize(self, dt, is_dst=False):
            '''Correct the timezone information on the given datetime'''
            if dt.tzinfo is self:
                return dt
            if dt.tzinfo is None:
                raise ValueError('Naive time - no tzinfo set')
            return dt.astimezone(self)

    def FixedOffset(offset, _tzinfos = {}):
        """return a fixed-offset timezone based off a number of minutes.

            >>> one = FixedOffset(-330)
            >>> one
            pytz.FixedOffset(-330)
            >>> one.utcoffset(datetime.datetime.now())
            datetime.timedelta(-1, 66600)
            >>> one.dst(datetime.datetime.now())
            datetime.timedelta(0)

            >>> two = FixedOffset(1380)
            >>> two
            pytz.FixedOffset(1380)
            >>> two.utcoffset(datetime.datetime.now())
            datetime.timedelta(0, 82800)
            >>> two.dst(datetime.datetime.now())
            datetime.timedelta(0)

        The datetime.timedelta must be between the range of -1 and 1 day,
        non-inclusive.

            >>> FixedOffset(1440)
            Traceback (most recent call last):
            ...
            ValueError: ('absolute offset is too large', 1440)

            >>> FixedOffset(-1440)
            Traceback (most recent call last):
            ...
            ValueError: ('absolute offset is too large', -1440)

        An offset of 0 is special-cased to return UTC.

            >>> FixedOffset(0) is UTC
            True

        There should always be only one instance of a FixedOffset per timedelta.
        This should be true for multiple creation calls.

            >>> FixedOffset(-330) is one
            True
            >>> FixedOffset(1380) is two
            True

        It should also be true for pickling.

            >>> import pickle
            >>> pickle.loads(pickle.dumps(one)) is one
            True
            >>> pickle.loads(pickle.dumps(two)) is two
            True
        """
        if offset == 0:
            return UTC

        info = _tzinfos.get(offset)
        if info is None:
            # We haven't seen this one before. we need to save it.

            # Use setdefault to avoid a race condition and make sure we have
            # only one
            info = _tzinfos.setdefault(offset, _FixedOffset(offset))

        return info

    FixedOffset.__safe_for_unpickling__ = True

    def _test():
        import doctest, os, sys
        sys.path.insert(0, os.pardir)
        import pytz
        return doctest.testmod(pytz)

    if __name__ == '__main__':
        _test()

    all_timezones = \
    ['Africa/Abidjan',
     'Africa/Accra',
     'Africa/Addis_Ababa',
     'Africa/Algiers',
     'Africa/Asmara',
     'Africa/Asmera',
     'Africa/Bamako',
     'Africa/Bangui',
     'Africa/Banjul',
     'Africa/Bissau',
     'Africa/Blantyre',
     'Africa/Brazzaville',
     'Africa/Bujumbura',
     'Africa/Cairo',
     'Africa/Casablanca',
     'Africa/Ceuta',
     'Africa/Conakry',
     'Africa/Dakar',
     'Africa/Dar_es_Salaam',
     'Africa/Djibouti',
     'Africa/Douala',
     'Africa/El_Aaiun',
     'Africa/Freetown',
     'Africa/Gaborone',
     'Africa/Harare',
     'Africa/Johannesburg',
     'Africa/Juba',
     'Africa/Kampala',
     'Africa/Khartoum',
     'Africa/Kigali',
     'Africa/Kinshasa',
     'Africa/Lagos',
     'Africa/Libreville',
     'Africa/Lome',
     'Africa/Luanda',
     'Africa/Lubumbashi',
     'Africa/Lusaka',
     'Africa/Malabo',
     'Africa/Maputo',
     'Africa/Maseru',
     'Africa/Mbabane',
     'Africa/Mogadishu',
     'Africa/Monrovia',
     'Africa/Nairobi',
     'Africa/Ndjamena',
     'Africa/Niamey',
     'Africa/Nouakchott',
     'Africa/Ouagadougou',
     'Africa/Porto-Novo',
     'Africa/Sao_Tome',
     'Africa/Timbuktu',
     'Africa/Tripoli',
     'Africa/Tunis',
     'Africa/Windhoek',
     'America/Adak',
     'America/Anchorage',
     'America/Anguilla',
     'America/Antigua',
     'America/Araguaina',
     'America/Argentina/Buenos_Aires',
     'America/Argentina/Catamarca',
     'America/Argentina/ComodRivadavia',
     'America/Argentina/Cordoba',
     'America/Argentina/Jujuy',
     'America/Argentina/La_Rioja',
     'America/Argentina/Mendoza',
     'America/Argentina/Rio_Gallegos',
     'America/Argentina/Salta',
     'America/Argentina/San_Juan',
     'America/Argentina/San_Luis',
     'America/Argentina/Tucuman',
     'America/Argentina/Ushuaia',
     'America/Aruba',
     'America/Asuncion',
     'America/Atikokan',
     'America/Atka',
     'America/Bahia',
     'America/Bahia_Banderas',
     'America/Barbados',
     'America/Belem',
     'America/Belize',
     'America/Blanc-Sablon',
     'America/Boa_Vista',
     'America/Bogota',
     'America/Boise',
     'America/Buenos_Aires',
     'America/Cambridge_Bay',
     'America/Campo_Grande',
     'America/Cancun',
     'America/Caracas',
     'America/Catamarca',
     'America/Cayenne',
     'America/Cayman',
     'America/Chicago',
     'America/Chihuahua',
     'America/Coral_Harbour',
     'America/Cordoba',
     'America/Costa_Rica',
     'America/Creston',
     'America/Cuiaba',
     'America/Curacao',
     'America/Danmarkshavn',
     'America/Dawson',
     'America/Dawson_Creek',
     'America/Denver',
     'America/Detroit',
     'America/Dominica',
     'America/Edmonton',
     'America/Eirunepe',
     'America/El_Salvador',
     'America/Ensenada',
     'America/Fort_Nelson',
     'America/Fort_Wayne',
     'America/Fortaleza',
     'America/Glace_Bay',
     'America/Godthab',
     'America/Goose_Bay',
     'America/Grand_Turk',
     'America/Grenada',
     'America/Guadeloupe',
     'America/Guatemala',
     'America/Guayaquil',
     'America/Guyana',
     'America/Halifax',
     'America/Havana',
     'America/Hermosillo',
     'America/Indiana/Indianapolis',
     'America/Indiana/Knox',
     'America/Indiana/Marengo',
     'America/Indiana/Petersburg',
     'America/Indiana/Tell_City',
     'America/Indiana/Vevay',
     'America/Indiana/Vincennes',
     'America/Indiana/Winamac',
     'America/Indianapolis',
     'America/Inuvik',
     'America/Iqaluit',
     'America/Jamaica',
     'America/Jujuy',
     'America/Juneau',
     'America/Kentucky/Louisville',
     'America/Kentucky/Monticello',
     'America/Knox_IN',
     'America/Kralendijk',
     'America/La_Paz',
     'America/Lima',
     'America/Los_Angeles',
     'America/Louisville',
     'America/Lower_Princes',
     'America/Maceio',
     'America/Managua',
     'America/Manaus',
     'America/Marigot',
     'America/Martinique',
     'America/Matamoros',
     'America/Mazatlan',
     'America/Mendoza',
     'America/Menominee',
     'America/Merida',
     'America/Metlakatla',
     'America/Mexico_City',
     'America/Miquelon',
     'America/Moncton',
     'America/Monterrey',
     'America/Montevideo',
     'America/Montreal',
     'America/Montserrat',
     'America/Nassau',
     'America/New_York',
     'America/Nipigon',
     'America/Nome',
     'America/Noronha',
     'America/North_Dakota/Beulah',
     'America/North_Dakota/Center',
     'America/North_Dakota/New_Salem',
     'America/Ojinaga',
     'America/Panama',
     'America/Pangnirtung',
     'America/Paramaribo',
     'America/Phoenix',
     'America/Port-au-Prince',
     'America/Port_of_Spain',
     'America/Porto_Acre',
     'America/Porto_Velho',
     'America/Puerto_Rico',
     'America/Punta_Arenas',
     'America/Rainy_River',
     'America/Rankin_Inlet',
     'America/Recife',
     'America/Regina',
     'America/Resolute',
     'America/Rio_Branco',
     'America/Rosario',
     'America/Santa_Isabel',
     'America/Santarem',
     'America/Santiago',
     'America/Santo_Domingo',
     'America/Sao_Paulo',
     'America/Scoresbysund',
     'America/Shiprock',
     'America/Sitka',
     'America/St_Barthelemy',
     'America/St_Johns',
     'America/St_Kitts',
     'America/St_Lucia',
     'America/St_Thomas',
     'America/St_Vincent',
     'America/Swift_Current',
     'America/Tegucigalpa',
     'America/Thule',
     'America/Thunder_Bay',
     'America/Tijuana',
     'America/Toronto',
     'America/Tortola',
     'America/Vancouver',
     'America/Virgin',
     'America/Whitehorse',
     'America/Winnipeg',
     'America/Yakutat',
     'America/Yellowknife',
     'Antarctica/Casey',
     'Antarctica/Davis',
     'Antarctica/DumontDUrville',
     'Antarctica/Macquarie',
     'Antarctica/Mawson',
     'Antarctica/McMurdo',
     'Antarctica/Palmer',
     'Antarctica/Rothera',
     'Antarctica/South_Pole',
     'Antarctica/Syowa',
     'Antarctica/Troll',
     'Antarctica/Vostok',
     'Arctic/Longyearbyen',
     'Asia/Aden',
     'Asia/Almaty',
     'Asia/Amman',
     'Asia/Anadyr',
     'Asia/Aqtau',
     'Asia/Aqtobe',
     'Asia/Ashgabat',
     'Asia/Ashkhabad',
     'Asia/Atyrau',
     'Asia/Baghdad',
     'Asia/Bahrain',
     'Asia/Baku',
     'Asia/Bangkok',
     'Asia/Barnaul',
     'Asia/Beirut',
     'Asia/Bishkek',
     'Asia/Brunei',
     'Asia/Calcutta',
     'Asia/Chita',
     'Asia/Choibalsan',
     'Asia/Chongqing',
     'Asia/Chungking',
     'Asia/Colombo',
     'Asia/Dacca',
     'Asia/Damascus',
     'Asia/Dhaka',
     'Asia/Dili',
     'Asia/Dubai',
     'Asia/Dushanbe',
     'Asia/Famagusta',
     'Asia/Gaza',
     'Asia/Harbin',
     'Asia/Hebron',
     'Asia/Ho_Chi_Minh',
     'Asia/Hong_Kong',
     'Asia/Hovd',
     'Asia/Irkutsk',
     'Asia/Istanbul',
     'Asia/Jakarta',
     'Asia/Jayapura',
     'Asia/Jerusalem',
     'Asia/Kabul',
     'Asia/Kamchatka',
     'Asia/Karachi',
     'Asia/Kashgar',
     'Asia/Kathmandu',
     'Asia/Katmandu',
     'Asia/Khandyga',
     'Asia/Kolkata',
     'Asia/Krasnoyarsk',
     'Asia/Kuala_Lumpur',
     'Asia/Kuching',
     'Asia/Kuwait',
     'Asia/Macao',
     'Asia/Macau',
     'Asia/Magadan',
     'Asia/Makassar',
     'Asia/Manila',
     'Asia/Muscat',
     'Asia/Nicosia',
     'Asia/Novokuznetsk',
     'Asia/Novosibirsk',
     'Asia/Omsk',
     'Asia/Oral',
     'Asia/Phnom_Penh',
     'Asia/Pontianak',
     'Asia/Pyongyang',
     'Asia/Qatar',
     'Asia/Qyzylorda',
     'Asia/Rangoon',
     'Asia/Riyadh',
     'Asia/Saigon',
     'Asia/Sakhalin',
     'Asia/Samarkand',
     'Asia/Seoul',
     'Asia/Shanghai',
     'Asia/Singapore',
     'Asia/Srednekolymsk',
     'Asia/Taipei',
     'Asia/Tashkent',
     'Asia/Tbilisi',
     'Asia/Tehran',
     'Asia/Tel_Aviv',
     'Asia/Thimbu',
     'Asia/Thimphu',
     'Asia/Tokyo',
     'Asia/Tomsk',
     'Asia/Ujung_Pandang',
     'Asia/Ulaanbaatar',
     'Asia/Ulan_Bator',
     'Asia/Urumqi',
     'Asia/Ust-Nera',
     'Asia/Vientiane',
     'Asia/Vladivostok',
     'Asia/Yakutsk',
     'Asia/Yangon',
     'Asia/Yekaterinburg',
     'Asia/Yerevan',
     'Atlantic/Azores',
     'Atlantic/Bermuda',
     'Atlantic/Canary',
     'Atlantic/Cape_Verde',
     'Atlantic/Faeroe',
     'Atlantic/Faroe',
     'Atlantic/Jan_Mayen',
     'Atlantic/Madeira',
     'Atlantic/Reykjavik',
     'Atlantic/South_Georgia',
     'Atlantic/St_Helena',
     'Atlantic/Stanley',
     'Australia/ACT',
     'Australia/Adelaide',
     'Australia/Brisbane',
     'Australia/Broken_Hill',
     'Australia/Canberra',
     'Australia/Currie',
     'Australia/Darwin',
     'Australia/Eucla',
     'Australia/Hobart',
     'Australia/LHI',
     'Australia/Lindeman',
     'Australia/Lord_Howe',
     'Australia/Melbourne',
     'Australia/NSW',
     'Australia/North',
     'Australia/Perth',
     'Australia/Queensland',
     'Australia/South',
     'Australia/Sydney',
     'Australia/Tasmania',
     'Australia/Victoria',
     'Australia/West',
     'Australia/Yancowinna',
     'Brazil/Acre',
     'Brazil/DeNoronha',
     'Brazil/East',
     'Brazil/West',
     'CET',
     'CST6CDT',
     'Canada/Atlantic',
     'Canada/Central',
     'Canada/East-Saskatchewan',
     'Canada/Eastern',
     'Canada/Mountain',
     'Canada/Newfoundland',
     'Canada/Pacific',
     'Canada/Saskatchewan',
     'Canada/Yukon',
     'Chile/Continental',
     'Chile/EasterIsland',
     'Cuba',
     'EET',
     'EST',
     'EST5EDT',
     'Egypt',
     'Eire',
     'Etc/GMT',
     'Etc/GMT+0',
     'Etc/GMT+1',
     'Etc/GMT+10',
     'Etc/GMT+11',
     'Etc/GMT+12',
     'Etc/GMT+2',
     'Etc/GMT+3',
     'Etc/GMT+4',
     'Etc/GMT+5',
     'Etc/GMT+6',
     'Etc/GMT+7',
     'Etc/GMT+8',
     'Etc/GMT+9',
     'Etc/GMT-0',
     'Etc/GMT-1',
     'Etc/GMT-10',
     'Etc/GMT-11',
     'Etc/GMT-12',
     'Etc/GMT-13',
     'Etc/GMT-14',
     'Etc/GMT-2',
     'Etc/GMT-3',
     'Etc/GMT-4',
     'Etc/GMT-5',
     'Etc/GMT-6',
     'Etc/GMT-7',
     'Etc/GMT-8',
     'Etc/GMT-9',
     'Etc/GMT0',
     'Etc/Greenwich',
     'Etc/UCT',
     'Etc/UTC',
     'Etc/Universal',
     'Etc/Zulu',
     'Europe/Amsterdam',
     'Europe/Andorra',
     'Europe/Astrakhan',
     'Europe/Athens',
     'Europe/Belfast',
     'Europe/Belgrade',
     'Europe/Berlin',
     'Europe/Bratislava',
     'Europe/Brussels',
     'Europe/Bucharest',
     'Europe/Budapest',
     'Europe/Busingen',
     'Europe/Chisinau',
     'Europe/Copenhagen',
     'Europe/Dublin',
     'Europe/Gibraltar',
     'Europe/Guernsey',
     'Europe/Helsinki',
     'Europe/Isle_of_Man',
     'Europe/Istanbul',
     'Europe/Jersey',
     'Europe/Kaliningrad',
     'Europe/Kiev',
     'Europe/Kirov',
     'Europe/Lisbon',
     'Europe/Ljubljana',
     'Europe/London',
     'Europe/Luxembourg',
     'Europe/Madrid',
     'Europe/Malta',
     'Europe/Mariehamn',
     'Europe/Minsk',
     'Europe/Monaco',
     'Europe/Moscow',
     'Europe/Nicosia',
     'Europe/Oslo',
     'Europe/Paris',
     'Europe/Podgorica',
     'Europe/Prague',
     'Europe/Riga',
     'Europe/Rome',
     'Europe/Samara',
     'Europe/San_Marino',
     'Europe/Sarajevo',
     'Europe/Saratov',
     'Europe/Simferopol',
     'Europe/Skopje',
     'Europe/Sofia',
     'Europe/Stockholm',
     'Europe/Tallinn',
     'Europe/Tirane',
     'Europe/Tiraspol',
     'Europe/Ulyanovsk',
     'Europe/Uzhgorod',
     'Europe/Vaduz',
     'Europe/Vatican',
     'Europe/Vienna',
     'Europe/Vilnius',
     'Europe/Volgograd',
     'Europe/Warsaw',
     'Europe/Zagreb',
     'Europe/Zaporozhye',
     'Europe/Zurich',
     'GB',
     'GB-Eire',
     'GMT',
     'GMT+0',
     'GMT-0',
     'GMT0',
     'Greenwich',
     'HST',
     'Hongkong',
     'Iceland',
     'Indian/Antananarivo',
     'Indian/Chagos',
     'Indian/Christmas',
     'Indian/Cocos',
     'Indian/Comoro',
     'Indian/Kerguelen',
     'Indian/Mahe',
     'Indian/Maldives',
     'Indian/Mauritius',
     'Indian/Mayotte',
     'Indian/Reunion',
     'Iran',
     'Israel',
     'Jamaica',
     'Japan',
     'Kwajalein',
     'Libya',
     'MET',
     'MST',
     'MST7MDT',
     'Mexico/BajaNorte',
     'Mexico/BajaSur',
     'Mexico/General',
     'NZ',
     'NZ-CHAT',
     'Navajo',
     'PRC',
     'PST8PDT',
     'Pacific/Apia',
     'Pacific/Auckland',
     'Pacific/Bougainville',
     'Pacific/Chatham',
     'Pacific/Chuuk',
     'Pacific/Easter',
     'Pacific/Efate',
     'Pacific/Enderbury',
     'Pacific/Fakaofo',
     'Pacific/Fiji',
     'Pacific/Funafuti',
     'Pacific/Galapagos',
     'Pacific/Gambier',
     'Pacific/Guadalcanal',
     'Pacific/Guam',
     'Pacific/Honolulu',
     'Pacific/Johnston',
     'Pacific/Kiritimati',
     'Pacific/Kosrae',
     'Pacific/Kwajalein',
     'Pacific/Majuro',
     'Pacific/Marquesas',
     'Pacific/Midway',
     'Pacific/Nauru',
     'Pacific/Niue',
     'Pacific/Norfolk',
     'Pacific/Noumea',
     'Pacific/Pago_Pago',
     'Pacific/Palau',
     'Pacific/Pitcairn',
     'Pacific/Pohnpei',
     'Pacific/Ponape',
     'Pacific/Port_Moresby',
     'Pacific/Rarotonga',
     'Pacific/Saipan',
     'Pacific/Samoa',
     'Pacific/Tahiti',
     'Pacific/Tarawa',
     'Pacific/Tongatapu',
     'Pacific/Truk',
     'Pacific/Wake',
     'Pacific/Wallis',
     'Pacific/Yap',
     'Poland',
     'Portugal',
     'ROC',
     'ROK',
     'Singapore',
     'Turkey',
     'UCT',
     'US/Alaska',
     'US/Aleutian',
     'US/Arizona',
     'US/Central',
     'US/East-Indiana',
     'US/Eastern',
     'US/Hawaii',
     'US/Indiana-Starke',
     'US/Michigan',
     'US/Mountain',
     'US/Pacific',
     'US/Pacific-New',
     'US/Samoa',
     'UTC',
     'Universal',
     'W-SU',
     'WET',
     'Zulu']
    all_timezones = LazyList(
            tz for tz in all_timezones if resource_exists(tz))

    all_timezones_set = LazySet(all_timezones)
    common_timezones = \
    ['Africa/Abidjan',
     'Africa/Accra',
     'Africa/Addis_Ababa',
     'Africa/Algiers',
     'Africa/Asmara',
     'Africa/Bamako',
     'Africa/Bangui',
     'Africa/Banjul',
     'Africa/Bissau',
     'Africa/Blantyre',
     'Africa/Brazzaville',
     'Africa/Bujumbura',
     'Africa/Cairo',
     'Africa/Casablanca',
     'Africa/Ceuta',
     'Africa/Conakry',
     'Africa/Dakar',
     'Africa/Dar_es_Salaam',
     'Africa/Djibouti',
     'Africa/Douala',
     'Africa/El_Aaiun',
     'Africa/Freetown',
     'Africa/Gaborone',
     'Africa/Harare',
     'Africa/Johannesburg',
     'Africa/Juba',
     'Africa/Kampala',
     'Africa/Khartoum',
     'Africa/Kigali',
     'Africa/Kinshasa',
     'Africa/Lagos',
     'Africa/Libreville',
     'Africa/Lome',
     'Africa/Luanda',
     'Africa/Lubumbashi',
     'Africa/Lusaka',
     'Africa/Malabo',
     'Africa/Maputo',
     'Africa/Maseru',
     'Africa/Mbabane',
     'Africa/Mogadishu',
     'Africa/Monrovia',
     'Africa/Nairobi',
     'Africa/Ndjamena',
     'Africa/Niamey',
     'Africa/Nouakchott',
     'Africa/Ouagadougou',
     'Africa/Porto-Novo',
     'Africa/Sao_Tome',
     'Africa/Tripoli',
     'Africa/Tunis',
     'Africa/Windhoek',
     'America/Adak',
     'America/Anchorage',
     'America/Anguilla',
     'America/Antigua',
     'America/Araguaina',
     'America/Argentina/Buenos_Aires',
     'America/Argentina/Catamarca',
     'America/Argentina/Cordoba',
     'America/Argentina/Jujuy',
     'America/Argentina/La_Rioja',
     'America/Argentina/Mendoza',
     'America/Argentina/Rio_Gallegos',
     'America/Argentina/Salta',
     'America/Argentina/San_Juan',
     'America/Argentina/San_Luis',
     'America/Argentina/Tucuman',
     'America/Argentina/Ushuaia',
     'America/Aruba',
     'America/Asuncion',
     'America/Atikokan',
     'America/Bahia',
     'America/Bahia_Banderas',
     'America/Barbados',
     'America/Belem',
     'America/Belize',
     'America/Blanc-Sablon',
     'America/Boa_Vista',
     'America/Bogota',
     'America/Boise',
     'America/Cambridge_Bay',
     'America/Campo_Grande',
     'America/Cancun',
     'America/Caracas',
     'America/Cayenne',
     'America/Cayman',
     'America/Chicago',
     'America/Chihuahua',
     'America/Costa_Rica',
     'America/Creston',
     'America/Cuiaba',
     'America/Curacao',
     'America/Danmarkshavn',
     'America/Dawson',
     'America/Dawson_Creek',
     'America/Denver',
     'America/Detroit',
     'America/Dominica',
     'America/Edmonton',
     'America/Eirunepe',
     'America/El_Salvador',
     'America/Fort_Nelson',
     'America/Fortaleza',
     'America/Glace_Bay',
     'America/Godthab',
     'America/Goose_Bay',
     'America/Grand_Turk',
     'America/Grenada',
     'America/Guadeloupe',
     'America/Guatemala',
     'America/Guayaquil',
     'America/Guyana',
     'America/Halifax',
     'America/Havana',
     'America/Hermosillo',
     'America/Indiana/Indianapolis',
     'America/Indiana/Knox',
     'America/Indiana/Marengo',
     'America/Indiana/Petersburg',
     'America/Indiana/Tell_City',
     'America/Indiana/Vevay',
     'America/Indiana/Vincennes',
     'America/Indiana/Winamac',
     'America/Inuvik',
     'America/Iqaluit',
     'America/Jamaica',
     'America/Juneau',
     'America/Kentucky/Louisville',
     'America/Kentucky/Monticello',
     'America/Kralendijk',
     'America/La_Paz',
     'America/Lima',
     'America/Los_Angeles',
     'America/Lower_Princes',
     'America/Maceio',
     'America/Managua',
     'America/Manaus',
     'America/Marigot',
     'America/Martinique',
     'America/Matamoros',
     'America/Mazatlan',
     'America/Menominee',
     'America/Merida',
     'America/Metlakatla',
     'America/Mexico_City',
     'America/Miquelon',
     'America/Moncton',
     'America/Monterrey',
     'America/Montevideo',
     'America/Montserrat',
     'America/Nassau',
     'America/New_York',
     'America/Nipigon',
     'America/Nome',
     'America/Noronha',
     'America/North_Dakota/Beulah',
     'America/North_Dakota/Center',
     'America/North_Dakota/New_Salem',
     'America/Ojinaga',
     'America/Panama',
     'America/Pangnirtung',
     'America/Paramaribo',
     'America/Phoenix',
     'America/Port-au-Prince',
     'America/Port_of_Spain',
     'America/Porto_Velho',
     'America/Puerto_Rico',
     'America/Punta_Arenas',
     'America/Rainy_River',
     'America/Rankin_Inlet',
     'America/Recife',
     'America/Regina',
     'America/Resolute',
     'America/Rio_Branco',
     'America/Santarem',
     'America/Santiago',
     'America/Santo_Domingo',
     'America/Sao_Paulo',
     'America/Scoresbysund',
     'America/Sitka',
     'America/St_Barthelemy',
     'America/St_Johns',
     'America/St_Kitts',
     'America/St_Lucia',
     'America/St_Thomas',
     'America/St_Vincent',
     'America/Swift_Current',
     'America/Tegucigalpa',
     'America/Thule',
     'America/Thunder_Bay',
     'America/Tijuana',
     'America/Toronto',
     'America/Tortola',
     'America/Vancouver',
     'America/Whitehorse',
     'America/Winnipeg',
     'America/Yakutat',
     'America/Yellowknife',
     'Antarctica/Casey',
     'Antarctica/Davis',
     'Antarctica/DumontDUrville',
     'Antarctica/Macquarie',
     'Antarctica/Mawson',
     'Antarctica/McMurdo',
     'Antarctica/Palmer',
     'Antarctica/Rothera',
     'Antarctica/Syowa',
     'Antarctica/Troll',
     'Antarctica/Vostok',
     'Arctic/Longyearbyen',
     'Asia/Aden',
     'Asia/Almaty',
     'Asia/Amman',
     'Asia/Anadyr',
     'Asia/Aqtau',
     'Asia/Aqtobe',
     'Asia/Ashgabat',
     'Asia/Atyrau',
     'Asia/Baghdad',
     'Asia/Bahrain',
     'Asia/Baku',
     'Asia/Bangkok',
     'Asia/Barnaul',
     'Asia/Beirut',
     'Asia/Bishkek',
     'Asia/Brunei',
     'Asia/Chita',
     'Asia/Choibalsan',
     'Asia/Colombo',
     'Asia/Damascus',
     'Asia/Dhaka',
     'Asia/Dili',
     'Asia/Dubai',
     'Asia/Dushanbe',
     'Asia/Famagusta',
     'Asia/Gaza',
     'Asia/Hebron',
     'Asia/Ho_Chi_Minh',
     'Asia/Hong_Kong',
     'Asia/Hovd',
     'Asia/Irkutsk',
     'Asia/Jakarta',
     'Asia/Jayapura',
     'Asia/Jerusalem',
     'Asia/Kabul',
     'Asia/Kamchatka',
     'Asia/Karachi',
     'Asia/Kathmandu',
     'Asia/Khandyga',
     'Asia/Kolkata',
     'Asia/Krasnoyarsk',
     'Asia/Kuala_Lumpur',
     'Asia/Kuching',
     'Asia/Kuwait',
     'Asia/Macau',
     'Asia/Magadan',
     'Asia/Makassar',
     'Asia/Manila',
     'Asia/Muscat',
     'Asia/Nicosia',
     'Asia/Novokuznetsk',
     'Asia/Novosibirsk',
     'Asia/Omsk',
     'Asia/Oral',
     'Asia/Phnom_Penh',
     'Asia/Pontianak',
     'Asia/Pyongyang',
     'Asia/Qatar',
     'Asia/Qyzylorda',
     'Asia/Riyadh',
     'Asia/Sakhalin',
     'Asia/Samarkand',
     'Asia/Seoul',
     'Asia/Shanghai',
     'Asia/Singapore',
     'Asia/Srednekolymsk',
     'Asia/Taipei',
     'Asia/Tashkent',
     'Asia/Tbilisi',
     'Asia/Tehran',
     'Asia/Thimphu',
     'Asia/Tokyo',
     'Asia/Tomsk',
     'Asia/Ulaanbaatar',
     'Asia/Urumqi',
     'Asia/Ust-Nera',
     'Asia/Vientiane',
     'Asia/Vladivostok',
     'Asia/Yakutsk',
     'Asia/Yangon',
     'Asia/Yekaterinburg',
     'Asia/Yerevan',
     'Atlantic/Azores',
     'Atlantic/Bermuda',
     'Atlantic/Canary',
     'Atlantic/Cape_Verde',
     'Atlantic/Faroe',
     'Atlantic/Madeira',
     'Atlantic/Reykjavik',
     'Atlantic/South_Georgia',
     'Atlantic/St_Helena',
     'Atlantic/Stanley',
     'Australia/Adelaide',
     'Australia/Brisbane',
     'Australia/Broken_Hill',
     'Australia/Currie',
     'Australia/Darwin',
     'Australia/Eucla',
     'Australia/Hobart',
     'Australia/Lindeman',
     'Australia/Lord_Howe',
     'Australia/Melbourne',
     'Australia/Perth',
     'Australia/Sydney',
     'Canada/Atlantic',
     'Canada/Central',
     'Canada/Eastern',
     'Canada/Mountain',
     'Canada/Newfoundland',
     'Canada/Pacific',
     'Europe/Amsterdam',
     'Europe/Andorra',
     'Europe/Astrakhan',
     'Europe/Athens',
     'Europe/Belgrade',
     'Europe/Berlin',
     'Europe/Bratislava',
     'Europe/Brussels',
     'Europe/Bucharest',
     'Europe/Budapest',
     'Europe/Busingen',
     'Europe/Chisinau',
     'Europe/Copenhagen',
     'Europe/Dublin',
     'Europe/Gibraltar',
     'Europe/Guernsey',
     'Europe/Helsinki',
     'Europe/Isle_of_Man',
     'Europe/Istanbul',
     'Europe/Jersey',
     'Europe/Kaliningrad',
     'Europe/Kiev',
     'Europe/Kirov',
     'Europe/Lisbon',
     'Europe/Ljubljana',
     'Europe/London',
     'Europe/Luxembourg',
     'Europe/Madrid',
     'Europe/Malta',
     'Europe/Mariehamn',
     'Europe/Minsk',
     'Europe/Monaco',
     'Europe/Moscow',
     'Europe/Oslo',
     'Europe/Paris',
     'Europe/Podgorica',
     'Europe/Prague',
     'Europe/Riga',
     'Europe/Rome',
     'Europe/Samara',
     'Europe/San_Marino',
     'Europe/Sarajevo',
     'Europe/Saratov',
     'Europe/Simferopol',
     'Europe/Skopje',
     'Europe/Sofia',
     'Europe/Stockholm',
     'Europe/Tallinn',
     'Europe/Tirane',
     'Europe/Ulyanovsk',
     'Europe/Uzhgorod',
     'Europe/Vaduz',
     'Europe/Vatican',
     'Europe/Vienna',
     'Europe/Vilnius',
     'Europe/Volgograd',
     'Europe/Warsaw',
     'Europe/Zagreb',
     'Europe/Zaporozhye',
     'Europe/Zurich',
     'GMT',
     'Indian/Antananarivo',
     'Indian/Chagos',
     'Indian/Christmas',
     'Indian/Cocos',
     'Indian/Comoro',
     'Indian/Kerguelen',
     'Indian/Mahe',
     'Indian/Maldives',
     'Indian/Mauritius',
     'Indian/Mayotte',
     'Indian/Reunion',
     'Pacific/Apia',
     'Pacific/Auckland',
     'Pacific/Bougainville',
     'Pacific/Chatham',
     'Pacific/Chuuk',
     'Pacific/Easter',
     'Pacific/Efate',
     'Pacific/Enderbury',
     'Pacific/Fakaofo',
     'Pacific/Fiji',
     'Pacific/Funafuti',
     'Pacific/Galapagos',
     'Pacific/Gambier',
     'Pacific/Guadalcanal',
     'Pacific/Guam',
     'Pacific/Honolulu',
     'Pacific/Kiritimati',
     'Pacific/Kosrae',
     'Pacific/Kwajalein',
     'Pacific/Majuro',
     'Pacific/Marquesas',
     'Pacific/Midway',
     'Pacific/Nauru',
     'Pacific/Niue',
     'Pacific/Norfolk',
     'Pacific/Noumea',
     'Pacific/Pago_Pago',
     'Pacific/Palau',
     'Pacific/Pitcairn',
     'Pacific/Pohnpei',
     'Pacific/Port_Moresby',
     'Pacific/Rarotonga',
     'Pacific/Saipan',
     'Pacific/Tahiti',
     'Pacific/Tarawa',
     'Pacific/Tongatapu',
     'Pacific/Wake',
     'Pacific/Wallis',
     'US/Alaska',
     'US/Arizona',
     'US/Central',
     'US/Eastern',
     'US/Hawaii',
     'US/Mountain',
     'US/Pacific',
     'UTC']
    common_timezones = LazyList(
                tz for tz in common_timezones if tz in all_timezones)

    common_timezones_set = LazySet(common_timezones)