Eho!!
I would like to make a contribution for the web design community today :-)
I've done this timezone list for using with wordpress plugins (actually for supersaas plugin).
(GMT-11:00) American Samoa|Pacific/Pago_Pago,
(GMT-10:00) Hawaii|Pacific/Honolulu,
(GMT-09:00) Alaska|America/Juneau,
(GMT-08:00) Pacific Time (US & Canada)|America/Los_Angeles,
(GMT-08:00) Tijuana|America/Tijuana,
(GMT-07:00) Arizona|America/Phoenix,
(GMT-07:00) Chihuahua|America/Chihuahua,
(GMT-07:00) Mazatlan|America/Mazatlan,
(GMT-07:00) Mountain Time (US & Canada)|America/Denver,
(GMT-06:00) Central America|America/Guatemala,
(GMT-06:00) Central Time (US & Canada)|America/Chicago,
(GMT-06:00) Mexico City|America/Mexico_City,
(GMT-06:00) Monterrey|America/Monterrey,
(GMT-06:00) Saskatchewan|America/Regina,
(GMT-05:00) Bogota|America/Bogota,
(GMT-05:00) Eastern Time (US & Canada)|America/New_York,
(GMT-05:00) Indiana (East)|America/Indiana/Indianapolis,
(GMT-05:00) Quito|America/Lima,
(GMT-04:30) Caracas|America/Caracas,
(GMT-04:00) Atlantic Time (Canada)|America/Halifax,
(GMT-04:00) Georgetown|America/Guyana,
(GMT-04:00) La Paz|America/La_Paz,
(GMT-04:00) Santiago|America/Santiago,
(GMT-03:30) Newfoundland|America/St_Johns,
(GMT-03:00) Brasilia|America/Sao_Paulo,
(GMT-03:00) Buenos Aires|America/Argentina/Buenos_Aires,
(GMT-03:00) Greenland|America/Godthab,
(GMT-02:00) Mid-Atlantic|Atlantic/South_Georgia,
(GMT-01:00) Azores|Atlantic/Azores,
(GMT-01:00) Cape Verde Is.|Atlantic/Cape_Verde,
(GMT+00:00) Casablanca|Africa/Casablanca,
(GMT+00:00) Dublin|Europe/Dublin,
(GMT+00:00) Lisbon|Europe/Lisbon,
(GMT+00:00) London|Europe/London,
(GMT+00:00) Monrovia|Africa/Monrovia,
(GMT+00:00) UTC|Etc/UTC,
(GMT+01:00) Amsterdam|Europe/Amsterdam,
(GMT+01:00) Belgrade|Europe/Belgrade,
(GMT+01:00) Berlin|Europe/Berlin,
(GMT+01:00) Bern|Europe/Zurich,
(GMT+01:00) Bratislava|Europe/Bratislava,
(GMT+01:00) Brussels|Europe/Brussels,
(GMT+01:00) Budapest|Europe/Budapest,
(GMT+01:00) Copenhagen|Europe/Copenhagen,
(GMT+01:00) Ljubljana|Europe/Ljubljana,
(GMT+01:00) Madrid|Europe/Madrid,
(GMT+01:00) Paris|Europe/Paris,
(GMT+01:00) Prague|Europe/Prague,
(GMT+01:00) Rome|Europe/Rome,
(GMT+01:00) Sarajevo|Europe/Sarajevo,
(GMT+01:00) Skopje|Europe/Skopje,
(GMT+01:00) Stockholm|Europe/Stockholm,
(GMT+01:00) Vienna|Europe/Vienna,
(GMT+01:00) Warsaw|Europe/Warsaw,
(GMT+01:00) West Central Africa|Africa/Algiers,
(GMT+01:00) Zagreb|Europe/Zagreb,
(GMT+02:00) Athens|Europe/Athens,
(GMT+02:00) Bucharest|Europe/Bucharest,
(GMT+02:00) Cairo|Africa/Cairo,
(GMT+02:00) Harare|Africa/Harare,
(GMT+02:00) Helsinki|Europe/Helsinki,
(GMT+02:00) Istanbul|Europe/Istanbul,
(GMT+02:00) Jerusalem|Asia/Jerusalem,
(GMT+02:00) Kyiv|Europe/Kiev,
(GMT+02:00) Pretoria|Africa/Johannesburg,
(GMT+02:00) Riga|Europe/Riga,
(GMT+02:00) Sofia|Europe/Sofia,
(GMT+02:00) Tallinn|Europe/Tallinn,
(GMT+02:00) Vilnius|Europe/Vilnius,
(GMT+03:00) Baghdad|Asia/Baghdad,
(GMT+03:00) Kuwait|Asia/Kuwait,
(GMT+03:00) Minsk|Europe/Minsk,
(GMT+03:00) Nairobi|Africa/Nairobi,
(GMT+03:00) Riyadh|Asia/Riyadh,
(GMT+03:30) Tehran|Asia/Tehran,
(GMT+04:00) Abu Dhabi|Asia/Muscat,
(GMT+04:00) Baku|Asia/Baku,
(GMT+04:00) Moscow|Europe/Moscow,
(GMT+04:00) Tbilisi|Asia/Tbilisi,
(GMT+04:00) Yerevan|Asia/Yerevan,
(GMT+04:30) Kabul|Asia/Kabul,
(GMT+05:00) Karachi|Asia/Karachi,
(GMT+05:00) Tashkent|Asia/Tashkent,
(GMT+05:30) New Delhi|Asia/Kolkata,
(GMT+05:30) Sri Jayawardenepura|Asia/Colombo,
(GMT+05:45) Kathmandu|Asia/Kathmandu,
(GMT+06:00) Almaty|Asia/Almaty,
(GMT+06:00) Dhaka|Asia/Dhaka,
(GMT+06:00) Ekaterinburg|Asia/Yekaterinburg,
(GMT+06:30) Rangoon|Asia/Rangoon,
(GMT+07:00) Bangkok|Asia/Bangkok,
(GMT+07:00) Jakarta|Asia/Jakarta,
(GMT+08:00) Beijing|Asia/Shanghai,
(GMT+08:00) Chongqing|Asia/Chongqing,
(GMT+08:00) Hong Kong|Asia/Hong_Kong,
(GMT+08:00) Krasnoyarsk|Asia/Krasnoyarsk,
(GMT+08:00) Kuala Lumpur|Asia/Kuala_Lumpur,
(GMT+08:00) Perth|Australia/Perth,
(GMT+08:00) Singapore|Asia/Singapore,
(GMT+08:00) Taipei|Asia/Taipei,
(GMT+08:00) Ulaan Bataar|Asia/Ulaanbaatar,
(GMT+08:00) Urumqi|Asia/Urumqi,
(GMT+09:00) Irkutsk|Asia/Irkutsk,
(GMT+09:00) Seoul|Asia/Seoul,
(GMT+09:00) Tokyo|Asia/Tokyo,
(GMT+09:30) Adelaide|Australia/Adelaide,
(GMT+09:30) Darwin|Australia/Darwin,
(GMT+10:00) Brisbane|Australia/Brisbane,
(GMT+10:00) Guam|Pacific/Guam,
(GMT+10:00) Hobart|Australia/Hobart,
(GMT+10:00) Melbourne|Australia/Melbourne,
(GMT+10:00) Port Moresby|Pacific/Port_Moresby,
(GMT+10:00) Sydney|Australia/Sydney,
(GMT+10:00) Yakutsk|Asia/Yakutsk,
(GMT+11:00) New Caledonia|Pacific/Noumea,
(GMT+11:00) Vladivostok|Asia/Vladivostok,
(GMT+12:00) Auckland|Pacific/Auckland,
(GMT+12:00) Fiji|Pacific/Fiji,
(GMT+12:00) Kamchatka|Asia/Kamchatka,
(GMT+12:00) Magadan|Asia/Magadan,
(GMT+12:00) Marshall Is.|Pacific/Majuro,
(GMT+13:00) Nuku'alofa|Pacific/Tongatapu,
(GMT+13:00) Samoa|Pacific/Apia,
By the way I would like to thank all the web design/development community, everyone who gave a solution on a forum, who made a plugin or any code and shared it with the world. Internet has grown so quickly because all of these web professionals that provide us lots of information for free.
I didn't find a formatted timezone list for wordpress plugins, so I did myself, and I hope by sharing this it will save time from other professionals.
Hope it will be useful for you ;-) please let a comment if it is!