JSON of GMT offsets and names of places for each of the offsets. Extracted from http://en.wikipedia.org/wiki/List_of_UTC_time_offsets

extract-from-page.js

// Run this code from the javascript console on the following wikipedia page to generate the output JSON: 
// http://en.wikipedia.org/wiki/List_of_UTC_time_offsets

var u = {}; 

function sr(k){  
	return function(){
		if($(this).text().indexOf('[')==-1)
		u[k].push($(this).text());  
	};
}

$('.mw-headline a').each(function(){  
	var key = $(this).text().replace(/UTC|\:/,'');
	u[key] = [];
	$(this).parent().parent().next('p').find('a').each(sr(key));
	$(this).parent().parent().next('ul').find('a').each(sr(key));
	$(this).parent().parent().next().next('ul').find('a').each(sr(key));
});

var outpt = JSON.stringify(u);
outpt;

gmt-offsets.json

{
    "−12:00": ["United States", "United States Minor Outlying Islands", "Baker Island", "Howland Island"],
    "−11:00": ["United States", "American Samoa", "Hawaii", "French Frigate Shoals", "Northwestern Hawaiian Islands", "United States Minor Outlying Islands", "Jarvis Island", "Kingman Reef", "Midway Atoll", "Palmyra Atoll", "New Zealand", "Niue"],
    "−10:00": ["Papeete", "Honolulu", "France", "French Polynesia", "Marquesas Islands", "Gambier Islands", "New Zealand", "Cook Islands", "United States", "Alaska", "Aleutian Islands", "Hawaii", "Necker Island", "United States Minor Outlying Islands", "Johnston Atoll"],
    "−09:30": ["France", "French Polynesia", "Marquesas Islands"],
    "−09:00": ["Anchorage", "France", "French Polynesia", "Gambier Islands", "United States", "Alaska Time Zone", "Alaska", "Aleutian Islands"],
    "−08:00": ["Los Angeles", "Vancouver", "Tijuana", "Canada", "British Columbia", "Cranbrook", "Golden", "Invermere", "Yukon", "France", "Clipperton Island", "Mexico", "Baja California", "United Kingdom", "Pitcairn Islands", "United States", "Pacific Time Zone", "California", "Idaho", "Salmon River", "Nevada", "West Wendover", "Oregon", "Malheur County", "Washington"],
    "−07:00": ["Phoenix", "Calgary", "Ciudad Juárez", "Canada", "Alberta", "British Columbia", "Cranbrook", "Golden", "Invermere", "Northwest Territories", "Nunavut", "Kitikmeot Region", "Saskatchewan", "Lloydminster", "Mexico", "Baja California Sur", "Chihuahua", "Nayarit", "Sinaloa", "Sonora", "United States", "Mountain Time Zone", "Arizona", "Colorado", "Idaho", "Salmon River", "Kansas", "Greeley", "Hamilton", "Sherman", "Wallace", "Montana", "Nebraska", "Cherry", "Hooker", "Arthur", "Keith", "Perkins", "Chase", "Dundy", "Nevada", "West Wendover", "New Mexico", "North Dakota", "Adams", "Billings", "Bowman", "Dunn", "Golden Valley", "Grant", "Hettinger", "McKenzie", "Sioux", "Slope", "Stark", "Oregon", "Malheur County", "South Dakota", "Corson", "Dewey", "Stanley", "Jackson", "Bennett", "Texas", "Culberson", "El Paso", "Hudspeth", "Utah", "Wyoming"],
    "−06:00": ["Chicago", "Guatemala City", "Mexico City", "San José", "San Salvador", "Tegucigalpa", "Winnipeg", "Belize", "Canada", "North American Central Time Zone", "Manitoba", "Nunavut", "Kivalliq Region", "Southampton Island", "Coral Harbour", "Ontario", "Northwestern Ontario", "Saskatchewan", "Lloydminster", "Creighton and Denare Beach area", "Chile", "Easter Island", "Costa Rica", "Ecuador", "Galápagos Islands", "El Salvador", "Guatemala", "Honduras", "Mexico", "Baja California", "Baja California Sur", "Chihuahua", "Nayarit", "Sinaloa", "Sonora", "Nicaragua", "United States", "Central Time Zone", "Alabama", "Phenix City", "Arkansas", "Florida", "Apalachicola River", "Franklin County", "Gulf County", "Intracoastal Waterway", "Illinois", "Indiana", "Jasper", "Lake", "LaPorte", "Newton", "Porter", "Starke", "Gibson", "Perry", "Posey", "Spencer", "Vanderburgh", "Warrick", "Iowa", "Kansas", "Kentucky", "Breckenridge", "Grayson", "Hart", "Green", "Adair", "Russell", "Clinton", "Louisiana", "Michigan", "Dickinson", "Gogebic", "Iron", "Menominee", "Minnesota", "Mississippi", "Missouri", "Nebraska", "Nebraska", "North Dakota", "Oklahoma", "Kenton", "South Dakota", "Tennessee", "Scott", "Morgan", "Roane", "Rhea", "Hamilton", "Texas", "Wisconsin"],
    "−05:00": ["New York", "Lima", "Toronto", "Bogotá", "Havana", "Kingston", "Bahamas", "Canada", "Nunavut", "Qikiqtaaluk Region", "Resolute", "Ontario", "Atikokan", "New Osnaburgh", "Pickle Lake", "Upsala", "Quebec", "Colombia", "Cuba", "Ecuador", "Haiti", "Jamaica", "Panama", "Peru", "United Kingdom", "Cayman Islands", "Turks and Caicos Islands", "United States", "Eastern Time", "Delaware", "District of Columbia", "Florida", "Calhoun", "Gulf", "Jackson", "Georgia", "Indiana", "Jasper", "Lake", "LaPorte", "Newton", "Porter", "Starke", "Gibson", "Perry", "Posey", "Spencer", "Vanderburgh", "Warrick", "Kentucky", "Breckenridge", "Grayson", "Hart", "Green", "Adair", "Russell", "Clinton", "Maryland", "Michigan", "Dickinson", "Gogebic", "Iron", "Menominee", "New England", "Connecticut", "Massachusetts", "Maine", "New Hampshire", "Rhode Island", "Vermont", "New Jersey", "New York", "North Carolina", "Ohio", "Pennsylvania", "South Carolina", "Tennessee", "Scott", "Morgan", "Roane", "Rhea", "Meigs", "Bradley", "Virginia", "West Virginia", "United States Minor Outlying Islands", "Navassa Island"],
    "−04:30": ["Caracas", "Venezuela"],
    "−04:00": ["Santiago", "La Paz", "San Juan de Puerto Rico", "Manaus", "Halifax", "Antigua and Barbuda", "Barbados", "Bolivia", "Brazil", "Acre", "Amazonas", "Mato Grosso", "Mato Grosso do Sul", "Rondônia", "Roraima", "Canada", "Atlantic Time Zone", "New Brunswick", "Newfoundland and Labrador", "Labrador", "L'Anse-au-Clair", "Nova Scotia", "Prince Edward Island", "Quebec", "Chile", "Denmark", "Greenland", "Qaanaaq (Thule)", "Pituffik", "Dominica", "Dominican Republic", "France", "Guadeloupe", "Martinique", "Saint Barthélemy", "Saint-Martin", "Grenada", "Guyana", "Netherlands", "Aruba", "Caribbean Netherlands", "Bonaire", "Saba", "Sint Eustatius", "Curaçao", "Sint Maarten", "Paraguay", "Saint Kitts and Nevis", "Saint Lucia", "Saint Vincent and the Grenadines", "Trinidad and Tobago", "United Kingdom", "Anguilla", "Bermuda", "British Virgin Islands", "Montserrat", "United States", "Puerto Rico", "U.S. Virgin Islands"],
    "−03:30": ["St. John's", "Canada", "Newfoundland Time Zone", "Newfoundland and Labrador", "Labrador", "L'Anse-au-Clair", "Newfoundland"],
    "−03:00": ["Buenos Aires", "Montevideo", "São Paulo", "Argentina", "Brazil", "Acre", "Amazonas", "Mato Grosso", "Mato Grosso do Sul", "Rondônia", "Roraima", "Denmark", "Greenland", "Qaanaaq", "Danmarkshavn", "Ittoqqortoormiit", "France", "French Guiana", "Saint-Pierre and Miquelon", "Suriname", "United Kingdom", "Falkland Islands", "Uruguay"],
    "−02:00": ["Brazil", "Fernando de Noronha", "United Kingdom", "South Georgia and the South Sandwich Islands"],
    "−01:00": ["Cape Verde", "Denmark", "Greenland", "Ittoqqortoormiit", "Portugal", "Azores"],
    "±00:00": ["Accra", "Abidjan", "Casablanca", "Dakar", "Dublin", "Lisbon", "London", "Burkina Faso", "Côte d'Ivoire", "Denmark", "Faroe Islands", "Greenland", "Danmarkshavn", "Gambia", "Ghana", "Guinea", "Guinea-Bissau", "Iceland", "Ireland", "Liberia", "Mali", "Mauritania", "Morocco", "Portugal", "Madeira", "Azores", "Sahrawi Republic", "limited recognition", "São Tomé and Príncipe", "Spain", "Canary Islands", "Senegal", "Sierra Leone", "Togo", "United Kingdom", "Guernsey", "Isle of Man", "Jersey", "Saint Helena, Ascension and Tristan da Cunha"],
    "+01:00": ["Amsterdam", "Belgrade", "Berlin", "Brussels", "Kinshasa", "Lagos", "Madrid", "Paris", "Rome", "Stockholm", "Tunis", "Warsaw", "Zurich", "Albania", "Algeria", "Andorra", "Angola", "Austria", "Belgium", "Benin", "Bosnia and Herzegovina", "Cameroon", "Central African Republic", "Chad", "Congo-Brazzaville", "Democratic Republic of the Congo", "Bandundu", "Bas-Congo", "Équateur", "Kinshasa", "Croatia", "Czech Republic", "Denmark", "Equatorial Guinea", "France", "Gabon", "Germany", "Hungary", "Italy", "Kosovo", "Libya", "Liechtenstein", "Luxembourg", "Macedonia", "Malta", "Monaco", "Montenegro", "Namibia", "Netherlands", "Niger", "Nigeria", "Norway", "Svalbard and Jan Mayen", "Poland", "San Marino", "Serbia", "Slovakia", "Slovenia", "Spain", "Balearic Islands", "Ceuta", "Melilla", "Canary Islands", "Sweden", "Switzerland", "Tunisia", "United Kingdom", "Gibraltar", "Vatican City"],
    "+02:00": ["Athens", "Sofia", "Cairo", "Kiev", "Istanbul", "Beirut", "Helsinki", "Jerusalem", "Johannesburg", "Bucharest", "Botswana", "Bulgaria", "Burundi", "Cyprus", "Northern Cyprus", "Democratic Republic of the Congo", "Kasaï Occidental", "Kasaï Oriental", "Katanga", "Maniema", "Nord-Kivu", "Orientale", "Sud-Kivu", "Egypt", "Estonia", "Finland", "Greece", "Israel", "Latvia", "Lebanon", "Lesotho", "Lithuania", "Malawi", "Moldova", "Mozambique", "Palestine", "Romania", "Rwanda", "South Africa", "Swaziland", "Syria", "Turkey", "Ukraine", "United Kingdom", "Akrotiri and Dhekelia", "Zambia", "Zimbabwe"],
    "+03:00": ["Nairobi", "Baghdad", "Doha", "Khartoum", "Minsk", "Riyadh", "Bahrain", "Belarus", "Comoros", "Djibouti", "Eritrea", "Ethiopia", "France", "French Southern and Antarctic Lands", "Scattered Islands in the Indian Ocean", "Bassas da India", "Europa Island", "Juan de Nova Island", "Mayotte", "Iraq", "Jordan", "Kenya", "Kuwait", "Madagascar", "Qatar", "Russia", "Northwestern Federal District", "Kaliningrad Oblast", "Saudi Arabia", "Somalia", "South Africa", "Prince Edward Islands", "Southern Sudan", "Sudan", "Tanzania", "Uganda", "Yemen"],
    "+03:30": ["Tehran", "Iran"],
    "+04:00": ["Baku", "Dubai", "Moscow", "Armenia", "Azerbaijan", "France", "French Southern and Antarctic Lands", "Crozet Islands", "Scattered Islands in the Indian Ocean", "Glorioso Islands", "Tromelin Island", "Réunion", "Georgia", "Mauritius", "Oman", "Russia", "Moscow Time", "Central Federal District", "North Caucasian Federal District", "Northwestern Federal District", "Kaliningrad Oblast", "Southern Federal District", "Volga Federal District", "Bashkortostan", "Orenburg Oblast", "Perm Krai", "Seychelles", "United Arab Emirates"],
    "+04:30": ["Kabul", "Afghanistan"],
    "+05:00": ["Karachi", "Tashkent", "Australia", "Heard Island and McDonald Islands", "France", "French Southern and Antarctic Lands", "Île Amsterdam", "Île Saint-Paul", "Kerguelen Islands", "Kazakhstan", "Aktobe", "Atyrau", "Mangystau", "West Kazakhstan", "Maldives", "Pakistan", "Tajikistan", "Turkmenistan", "Uzbekistan"],
    "+05:30": ["Colombo", "Delhi", "Mumbai", "India", "Sri Lanka"],
    "+05:45": ["Kathmandu", "Nepal"],
    "+06:00": ["Almaty", "Dhaka", "Yekaterinburg", "Bangladesh", "Bhutan", "Kazakhstan", "Aktobe", "Atyrau", "Mangystau", "West Kazakhstan", "Kyrgyzstan", "Russia", "Yekaterinburg Time", "Ural Federal District", "Volga Federal District", "Bashkortostan", "Orenburg Oblast", "Perm Krai", "United Kingdom", "British Indian Ocean Territory", "Chagos Archipelago", "Diego Garcia"],
    "+06:30": ["Yangon", "Australia", "Cocos (Keeling) Islands", "Myanmar"],
    "+07:00": ["Jakarta", "Bangkok", "Novosibirsk", "Hanoi", "Australia", "Christmas Island", "Cambodia", "Indonesia", "Java", "Sumatra", "West Kalimantan", "Central Kalimantan", "Laos", "Mongolia", "Hovd", "Russia", "Omsk Time", "Siberian Federal District", "Altai Krai", "Altai Republic", "Kemerovo Oblast", "Novosibirsk Oblast", "Omsk Oblast", "Tomsk Oblast", "Thailand", "Vietnam"],
    "+08:00": ["Perth", "Beijing", "Manila", "Singapore", "Kuala Lumpur", "Denpasar", "Krasnoyarsk", "Australia", "Western Australia", "Eucla", "Brunei", "China", "Indonesia", "East Kalimantan", "South Kalimantan", "Lesser Sunda Islands", "Sulawesi", "Malaysia", "Mongolia", "Ulaanbaatar", "Philippines", "Russia", "Krasnoyarsk Time", "Siberian Federal District", "Khakassia", "Krasnoyarsk Krai", "Tuva", "Singapore", "Taiwan"],
    "+08:45": ["Australia", "Western Australia", "Eucla"],
    "+09:00": ["Seoul", "Tokyo", "Pyongyang", "Ambon", "Irkutsk", "Indonesia", "Maluku Islands", "Papua", "West Papua", "Japan", "Japan Standard Time", "North Korea", "South Korea", "Korea Standard Time", "Palau", "Russia", "Irkutsk Time", "Siberian Federal District", "Buryatia", "Irkutsk Oblast", "Timor-Leste"],
    "+09:30": ["Adelaide", "Australia", "Northern Territory", "South Australia"],
    "+10:00": ["Canberra", "Yakutsk", "Port Moresby", "Australia", "Australian Capital Territory", "New South Wales", "Queensland", "Tasmania", "Victoria", "Federated States of Micronesia", "Chuuk", "Yap", "Papua New Guinea", "Russia", "Far Eastern Federal District", "Amur Oblast", "Zabaykalsky Krai", "Sakha Republic", "United States", "Guam", "Northern Mariana Islands"],
    "+10:30": ["Australia", "New South Wales", "Lord Howe Island"],
    "+11:00": ["Vladivostok", "Noumea", "Federated States of Micronesia", "Kosrae", "Pohnpei", "France", "New Caledonia", "Russia", "Vladivostok Time", "Far Eastern Federal District", "Primorsky Krai", "Jewish Autonomous Oblast", "Khabarovsk Krai", "Sakha Republic", "Sakhalin Island", "Solomon Islands", "Vanuatu"],
    "+11:30": ["Australia", "Norfolk Island"],
    "+12:00": ["Auckland", "Suva", "Antarctica", "Ross Dependency", "McMurdo Station", "Amundsen-Scott South Pole Station", "France", "Wallis and Futuna", "Fiji", "Kiribati", "Gilbert Islands", "Marshall Islands", "Nauru", "New Zealand", "Chatham Islands", "Russia", "Magadan Time", "Far Eastern Federal District", "Chukotka Autonomous Okrug", "Kamchatka Krai", "Magadan Oblast", "Sakha Republic", "Kuril Islands", "Tuvalu", "United States", "Wake Island"],
    "+12:45": ["New Zealand", "Chatham Islands"],
    "+13:00": ["Kiribati", "Phoenix Islands", "New Zealand", "Tokelau", "Samoa", "Tonga"],
    "+14:00": ["Kiribati", "Line Islands"]
}