tz: wrapper around TzDate class

<?php

class tz {

    public static $detection_failed = false;

    private static $timezone = 'UTC';

    private static $default_format = 'Y-m-d H:i:s';

    public static function zone()
    {
        return TzDate::default_timezone();
    }

    public static function date($timestamp = null)
    {
        if ($timestamp == null)
        {
            $timestamp = 'now';
        }
        else if (is_numeric($timestamp) and $timestamp > 0)
        {
            $timestamp = '@'.$timestamp;
        }

        return new TzDate($timestamp);
    }

    public static function utc($timestamp = null)
    {
        if ($timestamp == null)
        {
            $timestamp = 'now';
        }
        else if (is_numeric($timestamp) and $timestamp > 0)
        {
            $timestamp = '@'.$timestamp;
        }

        $dt = new TzDate($timestamp, TzDate::default_timezone());
        $dt->timezone('UTC');
        return $dt;
    }

    public static function set_default_timezone($timezone, $save = true)
    {
        $timezones = timezone_identifiers_list();
        if (! in_array($timezone, $timezones))
        {
            throw new Kohana_Exception('Attempted to set invalid timezone :tz: as default timezone', array(':tz:'=>$timezone));
        }

        TzDate::default_timezone($timezone);
        TzDate::default_format(self::$default_format);

        if ($save)
        {
            $sess = Session::instance();
            $sess->set('fmt_tz', $timezone);
        }
    }

    public static function get_timezone_by_offset($offset)
    {
        $zone = self::get_zone($offset);

        return $zone['timezone'];
    }

    public static function get_default_timezone()
    {
        $sess = Session::instance();

        $ex_tz = $sess->get('fmt_tz', null);

        if ($ex_tz === null)
        {
            $ex_tz = self::get_ip_default_timezone();

            if ($ex_tz === null)
            {
                self::$detection_failed = true;
                return 'UTC';
            }
        }

        return $ex_tz;
    }

    public static function get_ip_default_timezone()
    {
        return self::get_default_timezone_for_ip(Input::instance()->ip_address());
    }

    public static function get_default_timezone_for_ip($ip_address)
    {
        return KoGeoIP::timezone($ip_address);
    }

    public static function get_zones()
    {
        return self::$zones;
    }

    public static function get_zone($offset = 0)
    {
        $name = 'GMT'.sprintf('%+d', $offset);
        if (isset(self::$zones[$name]))
        {
            $zone = self::$zones[$name][0];
            $cities = self::$zones[$name][1];
            sort($cities);
            return array('timezone' => $zone, 'cities' => implode(', ', $cities), 'name' => $name, 'offset' => $offset);
        }
    }

    private static $zones = array(
        'GMT-11' => array(
            'Pacific/Niue',
            array('Niue', 'Midway', 'Pago Pago',),
        ),

        'GMT-10' => array(
            'Pacific/Tahiti',
            array('Hawaii', 'Tahiti', 'Adak', 'Honolulu', 'Rarotonga'),
        ),

        'GMT-9' => array(
            'Pacific/Gambier',
            array('Juneau', 'Yakutat', 'Nome', 'Anchorage', 'Gambier'),
        ),

        'GMT-8' => array(
            'Pacific/Pitcairn',
            array('Los Angeles', 'Vancouver', 'Whitehorse', 'Dawson', 'Tijuana'),
        ),

        'GMT-7' => array(
            'America/Dawson_Creek',
            array('Denver', 'Phoenix', 'Chiuaua', 'Ojinaga', 'Edmonton'),
        ),

        'GMT-6' => array(
            'America/Costa_Rica',
            array('Chicago', 'Mexico City', 'Winnipeg', 'Galapagos', 'Guatemala'),
        ),

        'GMT-5' => array(
            'America/Bogota',
            array('New York', 'Detroit', 'Toronto', 'Havana', 'Jamaica'),
        ),

        'GMT-4' => array(
            'America/Barbados',
            array('Barbados', 'Bermuda', 'Santiago', 'Puerto Rico', 'Caracas'),
        ),

        'GMT-3' => array(
            'America/Argentina/San_Juan',
            array('San Luis', 'Catamarca', 'Bahia', 'Cayenne', 'Montevideo'),
        ),

        'GMT-2' => array(
            'America/Noronha',
            array('South Georgia', 'Noronha'),
        ),

        'GMT-1' => array(
            'Atlantic/Cape_Verde',
            array('Cape Verde', 'Scoresbysund', 'Azores'),
        ),

        'GMT+0' => array(
            'Africa/Abidjan',
            array('London', 'Casablanca', 'Reykjavik', 'Lisbon', 'Dakar'),
        ),

        'GMT+1' => array(
            'Africa/Ndjamena',
            array('Berlin', 'Vienna', 'Douala', 'Tunis', 'Copenhagen', 'Zurich', 'Prague', 'Algiers', 'Madrid', 'Gibraltar', 'Rome', 'Monaco', 'Amsterdam', 'Oslo'),
        ),

        'GMT+2' => array(
            'Africa/Johannesburg',
            array('Johannesburg', 'Sofia', 'Minsk', 'Cairo', 'Helsinki', 'Beirut', 'Riga', 'Jerusalem', 'Gaza', 'Bucharest', 'Damascus', 'Kiev'),
        ),

        'GMT+3' => array(
            'Asia/Bahrain',
            array('Bahrain', 'Djibouti', 'Addis Ababa', 'Baghdad', 'Nairobi', 'Kuwait', 'Qatar', 'Moscow', 'Volgograd'),
        ),

        'GMT+4' => array(
            'Asia/Tbilisi',
            array('Dubai', 'Mauritius', 'Muscat', 'Mahe', 'Baku'),
        ),

        'GMT+5' => array(
            'Asia/Aqtobe',
            array('Oral', 'Maldives', 'Ashgabat', 'Dushanbe', 'Tashkent'),
        ),

        'GMT+6' => array(
            'Asia/Dhaka',
            array('Dhaka', 'Thimphu', 'Omsk', 'Novosibirsk', 'Chagos'),
        ),

        'GMT+7' => array(
            'Asia/Jakarta',
            array('Jakarta', 'Pontianak', 'Krasnoyarsk', 'Bangkok', 'Ho Chi Minh'),
        ),

        'GMT+8' => array(
            'Asia/Ulaanbaatar',
            array('Ulaanbaatar', 'Macau', 'Kuala Lumpur', 'Irkutsk', 'Singapore', 'Taipei', 'Perth', 'Brunei', 'Shanghai', 'Kashgar', 'Hong Kong'),
        ),

        'GMT+9' => array(
            'Pacific/Palau',
            array('Tokyo', 'Pyongyang', 'Seoul', 'Jayapura', 'Yakutsk'),
        ),

        'GMT+10' => array(
            'Australia/Brisbane',
            array('Brisbane', 'Hobart', 'Sydney', 'Truk', 'Guam', 'Vladivostok', 'Melbourne'),
        ),

        'GMT+11' => array(
            'Pacific/Ponape',
            array('Kamchatka', 'Magadan', 'Guadalcanal', 'Ponape', 'Noumea'),
        ),

        'GMT+12' => array(
            'Pacific/Funafuti',
            array('Wake', 'Wallis', 'Tarawa', 'Majuro', 'Nauru'),
        ),

        'GMT+13' => array(
            'Pacific/Enderbury',
            array('Enderbury', 'Tongatapu'),
        ),

        'GMT+14' => array(
            'Pacific/Kiritimati',
            array('Christmas Island'),
        ),
    );

}