TimezoneNameResolver.php

<?php

use DateTimeZone;

/**
 * Some timezone names are not officially "canonical", but rather an alias or alternative name.
 * This class resolves those to the correct timezone name.
 * https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
 */
final class TimezoneNameResolver {
    public const MAPPINGS = [
        'Africa/Accra' => 'Africa/Abidjan',
        'Africa/Addis_Ababa' => 'Africa/Nairobi',
        'Africa/Asmara' => 'Africa/Nairobi',
        'Africa/Bamako' => 'Africa/Abidjan',
        'Africa/Bangui' => 'Africa/Lagos',
        'Africa/Banjul' => 'Africa/Abidjan',
        'Africa/Blantyre' => 'Africa/Maputo',
        'Africa/Brazzaville' => 'Africa/Lagos',
        'Africa/Bujumbura' => 'Africa/Maputo',
        'Africa/Conakry' => 'Africa/Abidjan',
        'Africa/Dakar' => 'Africa/Abidjan',
        'Africa/Dar_es_Salaam' => 'Africa/Nairobi',
        'Africa/Djibouti' => 'Africa/Nairobi',
        'Africa/Douala' => 'Africa/Lagos',
        'Africa/Freetown' => 'Africa/Abidjan',
        'Africa/Gaborone' => 'Africa/Maputo',
        'Africa/Harare' => 'Africa/Maputo',
        'Africa/Kampala' => 'Africa/Nairobi',
        'Africa/Kigali' => 'Africa/Maputo',
        'Africa/Kinshasa' => 'Africa/Lagos',
        'Africa/Libreville' => 'Africa/Lagos',
        'Africa/Lome' => 'Africa/Abidjan',
        'Africa/Luanda' => 'Africa/Lagos',
        'Africa/Lubumbashi' => 'Africa/Maputo',
        'Africa/Lusaka' => 'Africa/Maputo',
        'Africa/Malabo' => 'Africa/Lagos',
        'Africa/Maseru' => 'Africa/Johannesburg',
        'Africa/Mbabane' => 'Africa/Johannesburg',
        'Africa/Mogadishu' => 'Africa/Nairobi',
        'Africa/Niamey' => 'Africa/Lagos',
        'Africa/Nouakchott' => 'Africa/Abidjan',
        'Africa/Ouagadougou' => 'Africa/Abidjan',
        'Africa/Porto-Novo' => 'Africa/Lagos',
        'Africa/Timbuktu' => 'Africa/Abidjan',
        'America/Anguilla' => 'America/Puerto_Rico',
        'America/Antigua' => 'America/Puerto_Rico',
        'America/Argentina/ComodRivadavia' => 'America/Argentina/Catamarca',
        'America/Aruba' => 'America/Puerto_Rico',
        'America/Atikokan' => 'America/Panama',
        'America/Blanc-Sablon' => 'America/Puerto_Rico',
        'America/Cayman' => 'America/Panama',
        'America/Coral_Harbour' => 'America/Panama',
        'America/Creston' => 'America/Phoenix',
        'America/Curacao' => 'America/Puerto_Rico',
        'America/Dominica' => 'America/Puerto_Rico',
        'America/Ensenada' => 'America/Tijuana',
        'America/Grenada' => 'America/Puerto_Rico',
        'America/Guadeloupe' => 'America/Puerto_Rico',
        'America/Montreal' => 'America/Toronto',
        'America/Montserrat' => 'America/Puerto_Rico',
        'America/Nassau' => 'America/Toronto',
        'America/Nipigon' => 'America/Toronto',
        'America/Pangnirtung' => 'America/Iqaluit',
        'America/Port_of_Spain' => 'America/Puerto_Rico',
        'America/Rainy_River' => 'America/Winnipeg',
        'America/Rosario' => 'America/Argentina/Cordoba',
        'America/St_Kitts' => 'America/Puerto_Rico',
        'America/St_Lucia' => 'America/Puerto_Rico',
        'America/St_Thomas' => 'America/Puerto_Rico',
        'America/St_Vincent' => 'America/Puerto_Rico',
        'America/Thunder_Bay' => 'America/Toronto',
        'America/Tortola' => 'America/Puerto_Rico',
        'America/Yellowknife' => 'America/Edmonton',
        'Antarctica/DumontDUrville' => 'Pacific/Port_Moresby',
        'Antarctica/McMurdo' => 'Pacific/Auckland',
        'Antarctica/Syowa' => 'Asia/Riyadh',
        'Asia/Aden' => 'Asia/Riyadh',
        'Asia/Bahrain' => 'Asia/Qatar',
        'Asia/Brunei' => 'Asia/Kuching',
        'Asia/Chongqing' => 'Asia/Shanghai',
        'Asia/Harbin' => 'Asia/Shanghai',
        'Asia/Kashgar' => 'Asia/Urumqi',
        'Asia/Kuala_Lumpur' => 'Asia/Singapore',
        'Asia/Kuwait' => 'Asia/Riyadh',
        'Asia/Muscat' => 'Asia/Dubai',
        'Asia/Phnom_Penh' => 'Asia/Bangkok',
        'Asia/Tel_Aviv' => 'Asia/Jerusalem',
        'Asia/Vientiane' => 'Asia/Bangkok',
        'Atlantic/Jan_Mayen' => 'Europe/Berlin',
        'Atlantic/Reykjavik' => 'Africa/Abidjan',
        'Atlantic/St_Helena' => 'Africa/Abidjan',
        'Australia/Currie' => 'Australia/Hobart',
        'Europe/Amsterdam' => 'Europe/Brussels',
        'Europe/Belfast' => 'Europe/London',
        'Europe/Copenhagen' => 'Europe/Berlin',
        'Europe/Guernsey' => 'Europe/London',
        'Europe/Isle_of_Man' => 'Europe/London',
        'Europe/Jersey' => 'Europe/London',
        'Europe/Ljubljana' => 'Europe/Belgrade',
        'Europe/Luxembourg' => 'Europe/Brussels',
        'Europe/Monaco' => 'Europe/Paris',
        'Europe/Oslo' => 'Europe/Berlin',
        'Europe/Sarajevo' => 'Europe/Belgrade',
        'Europe/Skopje' => 'Europe/Belgrade',
        'Europe/Stockholm' => 'Europe/Berlin',
        'Europe/Tiraspol' => 'Europe/Chisinau',
        'Europe/Uzhgorod' => 'Europe/Kyiv',
        'Europe/Vaduz' => 'Europe/Zurich',
        'Europe/Zagreb' => 'Europe/Belgrade',
        'Europe/Zaporozhye' => 'Europe/Kyiv',
        'Indian/Antananarivo' => 'Africa/Nairobi',
        'Indian/Christmas' => 'Asia/Bangkok',
        'Indian/Cocos' => 'Asia/Yangon',
        'Indian/Comoro' => 'Africa/Nairobi',
        'Indian/Kerguelen' => 'Indian/Maldives',
        'Indian/Mahe' => 'Asia/Dubai',
        'Indian/Mayotte' => 'Africa/Nairobi',
        'Indian/Reunion' => 'Asia/Dubai',
        'Pacific/Chuuk' => 'Pacific/Port_Moresby',
        'Pacific/Enderbury' => 'Pacific/Kanton',
        'Pacific/Funafuti' => 'Pacific/Tarawa',
        'Pacific/Johnston' => 'Pacific/Honolulu',
        'Pacific/Majuro' => 'Pacific/Tarawa',
        'Pacific/Midway' => 'Pacific/Pago_Pago',
        'Pacific/Pohnpei' => 'Pacific/Guadalcanal',
        'Pacific/Saipan' => 'Pacific/Guam',
        'Pacific/Wake' => 'Pacific/Tarawa',
        'Pacific/Wallis' => 'Pacific/Tarawa',
        'Africa/Asmera' => 'Africa/Nairobi',
        'America/Atka' => 'America/Adak',
        'America/Buenos_Aires' => 'America/Argentina/Buenos_Aires',
        'America/Catamarca' => 'America/Argentina/Catamarca',
        'America/Cordoba' => 'America/Argentina/Cordoba',
        'America/Fort_Wayne' => 'America/Indiana/Indianapolis',
        'America/Godthab' => 'America/Nuuk',
        'America/Indianapolis' => 'America/Indiana/Indianapolis',
        'America/Jujuy' => 'America/Argentina/Jujuy',
        'America/Knox_IN' => 'America/Indiana/Knox',
        'America/Kralendijk' => 'America/Puerto_Rico',
        'America/Louisville' => 'America/Kentucky/Louisville',
        'America/Lower_Princes' => 'America/Puerto_Rico',
        'America/Marigot' => 'America/Puerto_Rico',
        'America/Mendoza' => 'America/Argentina/Mendoza',
        'America/Porto_Acre' => 'America/Rio_Branco',
        'America/Santa_Isabel' => 'America/Tijuana',
        'America/Shiprock' => 'America/Denver',
        'America/St_Barthelemy' => 'America/Puerto_Rico',
        'America/Virgin' => 'America/Puerto_Rico',
        'Antarctica/South_Pole' => 'Pacific/Auckland',
        'Arctic/Longyearbyen' => 'Europe/Berlin',
        'Asia/Ashkhabad' => 'Asia/Ashgabat',
        'Asia/Calcutta' => 'Asia/Kolkata',
        'Asia/Chungking' => 'Asia/Shanghai',
        'Asia/Dacca' => 'Asia/Dhaka',
        'Asia/Istanbul' => 'Europe/Istanbul',
        'Asia/Katmandu' => 'Asia/Kathmandu',
        'Asia/Macao' => 'Asia/Macau',
        'Asia/Rangoon' => 'Asia/Yangon',
        'Asia/Saigon' => 'Asia/Ho_Chi_Minh',
        'Asia/Thimbu' => 'Asia/Thimphu',
        'Asia/Ujung_Pandang' => 'Asia/Makassar',
        'Asia/Ulan_Bator' => 'Asia/Ulaanbaatar',
        'Atlantic/Faeroe' => 'Atlantic/Faroe',
        'Australia/ACT' => 'Australia/Sydney',
        'Australia/Canberra' => 'Australia/Sydney',
        'Australia/LHI' => 'Australia/Lord_Howe',
        'Australia/North' => 'Australia/Darwin',
        'Australia/NSW' => 'Australia/Sydney',
        'Australia/Queensland' => 'Australia/Brisbane',
        'Australia/South' => 'Australia/Adelaide',
        'Australia/Tasmania' => 'Australia/Hobart',
        'Australia/Victoria' => 'Australia/Melbourne',
        'Australia/West' => 'Australia/Perth',
        'Australia/Yancowinna' => 'Australia/Broken_Hill',
        'Brazil/Acre' => 'America/Rio_Branco',
        'Brazil/DeNoronha' => 'America/Noronha',
        'Brazil/East' => 'America/Sao_Paulo',
        'Brazil/West' => 'America/Manaus',
        'Canada/Atlantic' => 'America/Halifax',
        'Canada/Central' => 'America/Winnipeg',
        'Canada/Eastern' => 'America/Toronto',
        'Canada/Mountain' => 'America/Edmonton',
        'Canada/Newfoundland' => 'America/St_Johns',
        'Canada/Pacific' => 'America/Vancouver',
        'Canada/Saskatchewan' => 'America/Regina',
        'Canada/Yukon' => 'America/Whitehorse',
        'Chile/Continental' => 'America/Santiago',
        'Chile/EasterIsland' => 'Pacific/Easter',
        'Cuba' => 'America/Havana',
        'Egypt' => 'Africa/Cairo',
        'Eire' => 'Europe/Dublin',
        'Etc/GMT+0' => 'Etc/GMT',
        'Etc/GMT-0' => 'Etc/GMT',
        'Etc/GMT0' => 'Etc/GMT',
        'Etc/Greenwich' => 'Etc/GMT',
        'Etc/UCT' => 'Etc/UTC',
        'Etc/Universal' => 'Etc/UTC',
        'Etc/Zulu' => 'Etc/UTC',
        'Europe/Bratislava' => 'Europe/Prague',
        'Europe/Busingen' => 'Europe/Zurich',
        'Europe/Kiev' => 'Europe/Kyiv',
        'Europe/Mariehamn' => 'Europe/Helsinki',
        'Europe/Nicosia' => 'Asia/Nicosia',
        'Europe/Podgorica' => 'Europe/Belgrade',
        'Europe/San_Marino' => 'Europe/Rome',
        'Europe/Vatican' => 'Europe/Rome',
        'GB' => 'Europe/London',
        'GB-Eire' => 'Europe/London',
        'GMT' => 'Etc/GMT',
        'GMT+0' => 'Etc/GMT',
        'GMT-0' => 'Etc/GMT',
        'GMT0' => 'Etc/GMT',
        'Greenwich' => 'Etc/GMT',
        'Hongkong' => 'Asia/Hong_Kong',
        'Iceland' => 'Africa/Abidjan',
        'Iran' => 'Asia/Tehran',
        'Israel' => 'Asia/Jerusalem',
        'Jamaica' => 'America/Jamaica',
        'Japan' => 'Asia/Tokyo',
        'Kwajalein' => 'Pacific/Kwajalein',
        'Libya' => 'Africa/Tripoli',
        'Mexico/BajaNorte' => 'America/Tijuana',
        'Mexico/BajaSur' => 'America/Mazatlan',
        'Mexico/General' => 'America/Mexico_City',
        'Navajo' => 'America/Denver',
        'NZ' => 'Pacific/Auckland',
        'NZ-CHAT' => 'Pacific/Chatham',
        'Pacific/Ponape' => 'Pacific/Guadalcanal',
        'Pacific/Samoa' => 'Pacific/Pago_Pago',
        'Pacific/Truk' => 'Pacific/Port_Moresby',
        'Pacific/Yap' => 'Pacific/Port_Moresby',
        'Poland' => 'Europe/Warsaw',
        'Portugal' => 'Europe/Lisbon',
        'PRC' => 'Asia/Shanghai',
        'ROC' => 'Asia/Taipei',
        'ROK' => 'Asia/Seoul',
        'Singapore' => 'Asia/Singapore',
        'Turkey' => 'Europe/Istanbul',
        'UCT' => 'Etc/UTC',
        'Universal' => 'Etc/UTC',
        'US/Alaska' => 'America/Anchorage',
        'US/Aleutian' => 'America/Adak',
        'US/Arizona' => 'America/Phoenix',
        'US/Central' => 'America/Chicago',
        'US/East-Indiana' => 'America/Indiana/Indianapolis',
        'US/Eastern' => 'America/New_York',
        'US/Hawaii' => 'Pacific/Honolulu',
        'US/Indiana-Starke' => 'America/Indiana/Knox',
        'US/Michigan' => 'America/Detroit',
        'US/Mountain' => 'America/Denver',
        'US/Pacific' => 'America/Los_Angeles',
        'US/Samoa' => 'Pacific/Pago_Pago',
        'UTC' => 'Etc/UTC',
        'W-SU' => 'Europe/Moscow',
        'Zulu' => 'Etc/UTC'
    ];

    public static function getCanonicalTimezone(string $timezone): ?string {
        if (array_key_exists($timezone, self::MAPPINGS)) {
            return self::MAPPINGS[$timezone];
        } else {
            try {
                $tz = new DateTimeZone($timezone);
                return $tz->getName();
            } catch (\Exception) {
                return null;
            }
        }
    }
}