This is simple. Just use the 'date_timezone' type, which is provided by date_api.module.
<?php
$form['timezone'] = array(
'#type' => 'date_timezone',
'#default_value' => $timezone,
'#description' => "Select a timezone if all the events will happen in the same place. Select that place's timezone",
);
?>
In the new system you just need to know the timezone name and either the UTC or local time. We store the UTC time and the timezone name in the database (in two separate fields). We retrieve that data and do:
<?php $date = the UTC value from the database $local_zone = the name of the local timezone $type = the type of date value, DATE_DATETIME, DATE_ISO, or DATE_UNIX $date = new DateObject($date, 'UTC', date_type_format($type)); date_timezone_set($date, timezone_open($local_zone); $date now contains the local value of the date. Output it like: print date_format_date($date, 'custom', 'm/d/Y H:i'); ?>
To convert a local date back to UTC to store it in the database, do:
<?php
$date = local date value
$local_zone = the name of the local timezone
$type = the type of date value, DATE_DATETIME, DATE_ISO, or DATE_UNIX
$date = new DateObject($date, $local_zone, $type);
date_timezone_set($date, timezone_open('UTC');
$date now contains the UTC value of the date.
Output it like:
print date_format_date($date, 'custom', 'm/d/Y H:i');
?>
The API doesn't handle timezone abbreviations at all, there's no way to do it right because they are not unique (EST could be Eastern Standard Time or European Summer Time). We need the full, undeprecated timezone name, which looks like 'America/Chicago'. It is comprised of the name of the continent and the major city in the timezone. Older names like 'US/Central' are deprecated because the area names change, but city names rarely do. Some good info about timezones is at http://en.wikipedia.org/wiki/Zoneinfo.
Also, we do not use spaces in the timezone names, so we use America/New_York, not America/New York. The PHP 5.2 date functions and MYSQL native timezone handling all expect names without spaces in them to work correctly.
You can use the php function timezone_name_from_abbr() to try to translate to and from abbreviations, but it's not entirely reliable, as noted above. If we have the current offset and we know if it's currently daylight savings time or not, you can combine that with the abbreviation to get the timezone name, but that's a lot of 'if's.
The complete list of allowed, undeprecated timezone names is:
Africa/Algiers Africa/Asmera Africa/Bangui Africa/Blantyre Africa/Brazzaville Africa/Bujumbura Africa/Cairo Africa/Ceuta Africa/Dar_es_Salaam Africa/Djibouti Africa/Douala Africa/Gaborone Africa/Harare Africa/Johannesburg Africa/Kampala Africa/Khartoum Africa/Kigali Africa/Kinshasa Africa/Lagos Africa/Libreville Africa/Luanda Africa/Lubumbashi Africa/Lusaka Africa/Malabo Africa/Maputo Africa/Maseru Africa/Mbabane Africa/Mogadishu Africa/Nairobi Africa/Ndjamena Africa/Niamey Africa/Porto-Novo Africa/Tripoli Africa/Tunis Africa/Windhoek America/Adak America/Anchorage America/Anguilla America/Antigua America/Araguaina America/Aruba America/Asuncion America/Atka America/Barbados America/Belem America/Belize America/Boa_Vista America/Bogota America/Boise America/Buenos_Aires America/Cambridge_Bay America/Cancun America/Caracas America/Catamarca America/Cayenne America/Cayman America/Chicago America/Chihuahua America/Cordoba America/Costa_Rica America/Cuiaba America/Curacao America/Dawson America/Dawson_Creek America/Denver America/Detroit America/Dominica America/Edmonton America/Eirunepe America/El_Salvador America/Ensenada 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/Vevay America/Indianapolis America/Inuvik America/Iqaluit America/Jamaica America/Jujuy America/Juneau America/Kentucky/Louisville America/Kentucky/Monticello America/Knox_IN America/La_Paz America/Lima America/Los_Angeles America/Louisville America/Maceio America/Managua America/Manaus America/Martinique America/Mazatlan America/Mendoza America/Menominee America/Merida America/Mexico_City America/Miquelon America/Monterrey America/Montevideo America/Montreal America/Montserrat America/Nassau America/New_York America/Nipigon America/Nome America/Noronha 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/Rainy_River America/Rankin_Inlet America/Recife America/Regina America/Rio_Branco America/Rosario America/Santiago America/Santo_Domingo America/Sao_Paulo America/Scoresbysund America/Shiprock 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/Tortola America/Vancouver America/Virgin America/Whitehorse America/Winnipeg America/Yakutat America/Yellowknife Antarctica/Casey Antarctica/Davis Antarctica/DumontDUrville Antarctica/Mawson Antarctica/McMurdo Antarctica/Palmer Antarctica/South_Pole Antarctica/Syowa Antarctica/Vostok Arctic/Longyearbyen Asia/Aden Asia/Almaty Asia/Amman Asia/Anadyr Asia/Aqtau Asia/Aqtobe Asia/Ashgabat Asia/Ashkhabad Asia/Baghdad Asia/Bahrain Asia/Baku Asia/Bangkok Asia/Beirut Asia/Bishkek Asia/Brunei Asia/Calcutta Asia/Chungking Asia/Colombo Asia/Dacca Asia/Damascus Asia/Dhaka Asia/Dili Asia/Dubai Asia/Dushanbe Asia/Gaza Asia/Harbin Asia/Hong_Kong Asia/Hovd Asia/Irkutsk Asia/Istanbul Asia/Jakarta Asia/Jayapura Asia/Jerusalem Asia/Kabul Asia/Kamchatka Asia/Karachi Asia/Kashgar Asia/Katmandu Asia/Krasnoyarsk Asia/Kuala_Lumpur Asia/Kuching Asia/Kuwait Asia/Macao Asia/Magadan Asia/Manila Asia/Muscat Asia/Nicosia Asia/Novosibirsk Asia/Omsk Asia/Phnom_Penh Asia/Pyongyang Asia/Qatar Asia/Rangoon Asia/Riyadh Asia/Riyadh87 Asia/Riyadh88 Asia/Riyadh89 Asia/Saigon Asia/Samarkand Asia/Seoul Asia/Shanghai Asia/Singapore Asia/Taipei Asia/Tashkent Asia/Tbilisi Asia/Tehran Asia/Tel_Aviv Asia/Thimbu Asia/Thimphu Asia/Tokyo Asia/Ujung_Pandang Asia/Ulaanbaatar Asia/Ulan_Bator Asia/Urumqi Asia/Vientiane Asia/Vladivostok Asia/Yakutsk Asia/Yekaterinburg Asia/Yerevan Atlantic/Azores Atlantic/Bermuda Atlantic/Canary Atlantic/Cape_Verde Atlantic/Faeroe Atlantic/Jan_Mayen Atlantic/Madeira Atlantic/South_Georgia Atlantic/Stanley Australia/ACT Australia/Adelaide Australia/Brisbane Australia/Broken_Hill Australia/Canberra Australia/Darwin 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 Europe/Amsterdam Europe/Andorra Europe/Athens Europe/Belfast Europe/Belgrade Europe/Berlin Europe/Bratislava Europe/Brussels Europe/Bucharest Europe/Budapest Europe/Chisinau Europe/Copenhagen Europe/Dublin Europe/Gibraltar Europe/Helsinki Europe/Istanbul Europe/Kaliningrad Europe/Kiev Europe/Lisbon Europe/Ljubljana Europe/London Europe/Luxembourg Europe/Madrid Europe/Malta Europe/Minsk Europe/Monaco Europe/Moscow Europe/Nicosia Europe/Oslo Europe/Paris Europe/Prague Europe/Riga Europe/Rome Europe/Samara Europe/San_Marino Europe/Sarajevo Europe/Simferopol Europe/Skopje Europe/Sofia Europe/Stockholm Europe/Tallinn Europe/Tirane Europe/Tiraspol Europe/Uzhgorod Europe/Vaduz Europe/Vatican Europe/Vienna Europe/Vilnius Europe/Warsaw Europe/Zagreb Europe/Zaporozhye Europe/Zurich 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/Chatham 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/Ponape Pacific/Port_Moresby Pacific/Rarotonga Pacific/Saipan Pacific/Samoa Pacific/Tahiti Pacific/Tarawa Pacific/Tongatapu Pacific/Truk Pacific/Wake Pacific/Wallis Pacific/Yap Pacific/French_Polynesia-Marquesas_Islands UTC