Get timezone abbreviation from date object or date string

timezone_abbreviation.js

var timezoneAbbreviation = function(timezoneString) {
    var timezoneAbbreviations = {
        "Afghanistan Time": "AFT",
        "Alaska Daylight Time": "AKDT",
        "Alaska Standard Time": "AKST",
        "Amazon Summer Time": "AMST",
        "Amazon Time": "AMT",
        "Arabia Standard Time": "AST",
        "Argentina Time": "ART",
        "Armenia Summer Time": "AMST",
        "Armenia Time": "AMT",
        "ASEAN Common Time": "ACT",
        "Atlantic Daylight Time": "ADT",
        "Atlantic Standard Time": "AST",
        "Australian Central Daylight Savings Time": "ACDT",
        "Australian Central Standard Time": "ACST",
        "Australian Eastern Daylight Savings Time": "AEDT",
        "Australian Eastern Standard Time": "AEST",
        "Australian Western Daylight Time": "AWDT",
        "Australian Western Standard Time": "AWST",
        "Azerbaijan Time": "AZT",
        "Azores Standard Time": "AZOST",
        "Baker Island Time": "BIT",
        "Bangladesh Standard Time": "BST",
        "Bhutan Time": "BTT",
        "Bolivia Time": "BOT",
        "Brasilia Time": "BRT",
        "British Indian Ocean Time": "BIOT",
        "British Summer Time": "BST",
        "Brunei Time": "BDT",
        "Cape Verde Time": "CVT",
        "Central Africa Time": "CAT",
        "Central Daylight Time": "CDT",
        "Central European Daylight Time": "CEDT",
        "Central European Summer Time": "CEST",
        "Central European Time": "CET",
        "Central Indonesia Time": "CIT",
        "Central Standard Time": "CST",
        "Central Summer Time": "CST",
        "Central Western Standard Time": "CWST",
        "Chamorro Standard Time": "ChST",
        "Chatham Daylight Time": "CHADT",
        "Chatham Standard Time": "CHAST",
        "Chile Standard Time": "CLT",
        "Chile Summer Time": "CLST",
        "China Standard Time": "CST",
        "China time": "CT",
        "Choibalsan": "CHOT",
        "Christmas Island Time": "CXT",
        "Chuuk Time": "CHUT",
        "Clipperton Island Standard Time": "CIST",
        "Cocos Islands Time": "CCT",
        "Colombia Summer Time": "COST",
        "Colombia Time": "COT",
        "Cook Island Time": "CKT",
        "Coordinated Universal Time UTC": "UTC",
        "Cuba Daylight Time": "CDT",
        "Cuba Standard Time": "CST",
        "Davis Time": "DAVT",
        "Dumont d'Urville Time": "DDUT",
        "East Africa Time": "EAT",
        "Easter Island Standard Summer Time": "EASST",
        "Easter Island Standard Time": "EAST",
        "Eastern Caribbean Time": "ECT",
        "Eastern Daylight Time": "EDT",
        "Eastern European Daylight Time": "EEDT",
        "Eastern European Summer Time": "EEST",
        "Eastern European Time": "EET",
        "Eastern Greenland Summer Time": "EGST",
        "Eastern Greenland Time": "EGT",
        "Eastern Indonesian Time": "EIT",
        "Eastern Standard Time": "EST",
        "Ecuador Time": "ECT",
        "Falkland Islands Standard Time": "FKST",
        "Falkland Islands Summer Time": "FKST",
        "Falkland Islands Time": "FKT",
        "Fernando de Noronha Time": "FNT",
        "Fiji Time": "FJT",
        "French Guiana Time": "GFT",
        "Further-eastern European Time": "FET",
        "Galapagos Time": "GALT",
        "Gambier Island Time": "GIT",
        "Gambier Islands": "GAMT",
        "Georgia Standard Time": "GET",
        "Gilbert Island Time": "GILT",
        "Greenwich Mean Time UTC": "GMT",
        "Gulf Standard Time": "GST",
        "Guyana Time": "GYT",
        "Hawaii Standard Time": "HST",
        "Hawaii-Aleutian Daylight Time": "HADT",
        "Hawaii-Aleutian Standard Time": "HAST",
        "Heard and McDonald Islands Time": "HMT",
        "Heure Avancée d'Europe Centrale": "HAEC",
        "Hong Kong Time": "HKT",
        "Indian Ocean Time": "IOT",
        "Indian Standard Time": "IST",
        "Indian/Kerguelen": "TFT",
        "Indochina Time": "ICT",
        "Iran Daylight Time": "IRDT",
        "Iran Standard Time": "IRST",
        "Irish Standard Time": "IST",
        "Irkutsk Time": "IRKT",
        "Israel Daylight Time": "IDT",
        "Israel Standard Time": "IST",
        "Japan Standard Time": "JST",
        "Kaliningrad Time": "USZ1",
        "Kamchatka Time": "PETT",
        "Khovd Time": "HOVT",
        "Korea Standard Time": "KST",
        "Kosrae Time": "KOST",
        "Krasnoyarsk Time": "KRAT",
        "Kyrgyzstan time": "KGT",
        "Line Islands Time": "LINT",
        "Lord Howe Standard Time": "LHST",
        "Lord Howe Summer Time": "LHST",
        "Macquarie Island Station Time": "MIST",
        "Magadan Time": "MAGT",
        "Malaysia Standard Time": "MST",
        "Malaysia Time": "MYT",
        "Maldives Time": "MVT",
        "Marquesas Islands Time": "MART",
        "Marshall Islands": "MHT",
        "Mauritius Time": "MUT",
        "Mawson Station Time": "MAWT",
        "Middle European Saving Time": "MEST",
        "Middle European Time": "MET",
        "Moscow Time": "MSK",
        "Mountain Daylight Time": "MDT",
        "Mountain Standard Time": "MST",
        "Myanmar Standard Time": "MST",
        "Myanmar Time": "MMT",
        "Nepal Time": "NPT",
        "New Caledonia Time": "NCT",
        "New Zealand Daylight Time": "NZDT",
        "New Zealand Standard Time": "NZST",
        "Newfoundland Daylight Time": "NDT",
        "Newfoundland Standard Time": "NST",
        "Newfoundland Time": "NT",
        "Niue Time": "NUT",
        "Norfolk Time": "NFT",
        "Omsk Time": "OMST",
        "Oral Time": "ORAT",
        "Pacific Daylight Time": "PDT",
        "Pacific Standard Time": "PST",
        "Pakistan Standard Time": "PKT",
        "Papua New Guinea Time": "PGT",
        "Paraguay Summer Time": "PYST",
        "Paraguay Time": "PYT",
        "Peru Time": "PET",
        "Philippine Standard Time": "PST",
        "Phoenix Island Time": "PHOT",
        "Pohnpei Standard Time": "PONT",
        "Rothera Research Station Time": "ROTT",
        "Réunion Time": "RET",
        "Saint Pierre and Miquelon Daylight Time": "PMDT",
        "Saint Pierre and Miquelon Standard Time": "PMST",
        "Sakhalin Island time": "SAKT",
        "Samara Time": "SAMT",
        "Samoa Standard Time": "SST",
        "Seychelles Time": "SCT",
        "Showa Station Time": "SYOT",
        "Singapore Standard Time": "SST",
        "Singapore Time": "SGT",
        "Solomon Islands Time": "SBT",
        "South African Standard Time": "SAST",
        "South Georgia and the South Sandwich Islands": "GST",
        "Srednekolymsk Time": "SRET",
        "Sri Lanka Time": "SLST",
        "Suriname Time": "SRT",
        "Tahiti Time": "TAHT",
        "Tajikistan Time": "TJT",
        "Thailand Standard Time": "THA",
        "Timor Leste Time": "TLT",
        "Tokelau Time": "TKT",
        "Tonga Time": "TOT",
        "Turkmenistan Time": "TMT",
        "Tuvalu Time": "TVT",
        "Ulaanbaatar Time": "ULAT",
        "Uruguay Standard Time": "UYT",
        "Uruguay Summer Time": "UYST",
        "Uzbekistan Time": "UZT",
        "Vanuatu Time": "VUT",
        "Venezuelan Standard Time": "VET",
        "Vladivostok Time": "VLAT",
        "Volgograd Time": "VOLT",
        "Vostok Station Time": "VOST",
        "Wake Island Time": "WAKT",
        "West Africa Summer Time": "WAST",
        "West Africa Time": "WAT",
        "Western European Daylight Time": "WEDT",
        "Western European Summer Time": "WEST",
        "Western European Time UTC": "WET",
        "Western Indonesian Time": "WIT",
        "Western Standard Time": "WST",
        "Yakutsk Time": "YAKT",
        "Yekaterinburg Time": "YEKT",
        "Zulu Time": "Z"
    };
    return timezoneAbbreviations[timezoneString] || timezoneString;
};

var getTimezoneAbbreviation = function(date) {
    var match;
    date = date.toString();
    // Wed Feb 29 2012 00:00:00 GMT-0800 (Pacific Standard Time)
    // Wed Feb 29 2012 00:00:00 GMT-0800 (PST)
    if (match = date.match(/\((.+)\)/)) {
        return timezoneAbbreviation(match[1].valueOf());
    }
    // Wed Feb 29 00:00:00 PST 2012
    else if (match = date.match(/\d{2}:\d{2}:\d{2}\s(\w{1,5})\s/)) {
        return match[1].valueOf();
    }
};