Coordinated Universal Time

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Coordinated Universal Time comes from the French word Temps universel coordonné, abbreviated as UTC, and is the successor to Greenwich Mean Time (GMT).  It is the primary standard of time by which the world regulates time and does not observe daylight saving time.

UTC was officially formalized in 1960 by the International Radio Consultative Committee in Recommendation having been initiated by several national time laboratories.  The current version of UTC is defined by International Telecommunications Union Recommendation (ITU-R TF.460-6), Standard-frequency and time-signal emissions and is based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the slowing of Earth’s rotation.  Leap seconds are inserted as necessary to keep UTC within 0.9 seconds of universal time, UT1.

Time zones around the world are expressed using positive or negative offsets from UTC, as in the list of time zones by UTC offset.

UTC is used in many Internet and World Wide Web standards.  The Network Time Protocol, designed to synchronize the clocks of computers over the Internet, encodes times using the UTC system.  Computer servers, online services and other entities that rely on having a universally accepted time use UTC as it is more specific than GMT.

Time zones are usually defined as differing from UTC by an integer number of hours, although the laws of each jurisdiction would have to be consulted if sub-second accuracy was required.  Several jurisdictions have established time zones that differ by an integer number of half-hours or quarter-hours from UT1 or UTC.

UTC does not change with a change of seasons, but local time or civil time may change if a time zone jurisdiction observes daylight saving time (summer time). For example, local time on the east coast of the United States is five hours behind UTC during winter, but four hours behind while daylight saving is observed there.

Time Zone NameCountry or Territory
Dateline Standard Time(UTC-12:00) International Date Line West
Samoa Standard Time(UTC-11:00) Samoa
Hawaiian Standard Time(UTC-10:00) Hawaii
Alaskan Standard Time(UTC-09:00) Alaska
Pacific Standard Time(UTC-08:00) Pacific Time (US and Canada)
Pacific Standard Time (Mexico)(UTC-08:00) Baja California
Mountain Standard Time(UTC-07:00) Mountain Time (US and Canada)
Mountain Standard Time (Mexico)(UTC-07:00) Chihuahua, La Paz, Mazatlan
US Mountain Standard Time(UTC-07:00) Arizona
Canada Central Standard Time(UTC-06:00) Saskatchewan
Central America Standard Time(UTC-06:00) Central America
Central Standard Time(UTC-06:00) Central Time (US and Canada)
Central Standard Time (Mexico)(UTC-06:00) Guadalajara, Mexico City, Monterrey
Eastern Standard Time(UTC-05:00) Eastern Time (US and Canada)
SA Pacific Standard Time(UTC-05:00) Bogota, Lima, Quito
US Eastern Standard Time(UTC-05:00) Indiana (East)
Venezuela Standard Time(UTC-04:30) Caracas
Atlantic Standard Time(UTC-04:00) Atlantic Time (Canada)
Central Brazilian Standard Time(UTC-04:00) Cuiaba
Pacific SA Standard Time(UTC-04:00) Santiago
SA Western Standard Time(UTC-04:00) Georgetown, La Paz, Manaus, San Juan
Paraguay Standard Time(UTC-04:00) Asuncion
Newfoundland Standard Time(UTC-03:30) Newfoundland
E. South America Standard Time(UTC-03:00) Brasilia
Greenland Standard Time(UTC-03:00) Greenland
Montevideo Standard Time(UTC-03:00) Montevideo
SA Eastern Standard Time(UTC-03:00) Cayenne, Fortaleza
Argentina Standard Time(UTC-03:00) Buenos Aires
Mid-Atlantic Standard Time(UTC-02:00) Mid-Atlantic
Azores Standard Time(UTC-01:00) Azores
Cabo Verde Standard Time(UTC-01:00) Cabo Verde Is.
GMT Standard Time(UTC) Dublin, Edinburgh, Lisbon, London
Greenwich Standard Time(UTC) Monrovia, Reykjavik
Morocco Standard Time(UTC) Casablanca
UTC(UTC) Coordinated Universal Time
Central Europe Standard Time(UTC+01:00) Belgrade, Bratislava, Budapest, Ljubljana, Prague
Central European Standard Time(UTC+01:00) Sarajevo, Skopje, Warsaw, Zagreb
Romance Standard Time(UTC+01:00) Brussels, Copenhagen, Madrid, Paris
W. Central Africa Standard Time(UTC+01:00) West Central Africa
W. Europe Standard Time(UTC+01:00) Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna
Namibia Standard Time(UTC+01:00) Windhoek
E. Europe Standard Time(UTC+02:00) Minsk
Egypt Standard Time(UTC+02:00) Cairo
FLE Standard Time(UTC+02:00) Helsinki, Kyiv, Riga, Sofia, Tallinn, Vilnius
GTB Standard Time(UTC+02:00) Athens, Bucharest
Israel Standard Time(UTC+02:00) Jerusalem
Jordan Standard Time(UTC+02:00) Amman
Middle East Standard Time(UTC+02:00) Beirut
South Africa Standard Time(UTC+02:00) Harare, Pretoria
Syria Standard Time(UTC+02:00) Damascus
Turkey Standard Time(UTC+02:00) Istanbul
Arab Standard Time(UTC+03:00) Kuwait, Riyadh
Arabic Standard Time(UTC+03:00) Baghdad
E. Africa Standard Time(UTC+03:00) Nairobi
Kaliningrad Standard Time(UTC+03:00) Kaliningrad
Iran Standard Time(UTC+03:30) Tehran
Russian Standard Time(UTC+04:00) Moscow, St. Petersburg, Volgograd
Arabian Standard Time(UTC+04:00) Abu Dhabi, Muscat
Azerbaijan Standard Time(UTC+04:00) Baku
Caucasus Standard Time(UTC+04:00) Yerevan
Georgian Standard Time(UTC+04:00) Tbilisi
Mauritius Standard Time(UTC+04:00) Port Louis
Afghanistan Standard Time(UTC+04:30) Kabul
West Asia Standard Time(UTC+05:00) Tashkent
Pakistan Standard Time(UTC+05:00) Islamabad, Karachi
India Standard Time(UTC+05:30) Chennai, Kolkata, Mumbai, New Delhi
Sri Lanka Standard Time(UTC+05:30) Sri Jayawardenepura
Nepal Standard Time(UTC+05:45) Kathmandu
Ekaterinburg Standard Time(UTC+06:00) Ekaterinburg
Central Asia Standard Time(UTC+06:00) Astana
Bangladesh Standard Time(UTC+06:00) Dhaka
Myanmar Standard Time(UTC+06:30) Yangon (Rangoon)
N. Central Asia Standard Time(UTC+07:00) Novosibirsk
SE Asia Standard Time(UTC+07:00) Bangkok, Hanoi, Jakarta
North Asia Standard Time(UTC+08:00) Krasnoyarsk
China Standard Time(UTC+08:00) Beijing, Chongqing, Hong Kong, Urumqi
Singapore Standard Time(UTC+08:00) Kuala Lumpur, Singapore
Taipei Standard Time(UTC+08:00) Taipei
W. Australia Standard Time(UTC+08:00) Perth
Ulaanbaatar Standard Time(UTC+08:00) Ulaanbaatar
North Asia East Standard Time(UTC+09:00) Irkutsk
Korea Standard Time(UTC+09:00) Seoul
Tokyo Standard Time(UTC+09:00) Osaka, Sapporo, Tokyo
AUS Central Standard Time(UTC+09:30) Darwin
Cen. Australia Standard Time(UTC+09:30) Adelaide
Yakutsk Standard Time(UTC+10:00) Yakutsk
AUS Eastern Standard Time(UTC+10:00) Canberra, Melbourne, Sydney
E. Australia Standard Time(UTC+10:00) Brisbane
Tasmania Standard Time(UTC+10:00) Hobart
West Pacific Standard Time(UTC+10:00) Guam, Port Moresby
Vladivostok Standard Time(UTC+11:00) Vladivostok
Central Pacific Standard Time(UTC+11:00) Solomon Is., New Caledonia
Magadan Standard Time(UTC+12:00) Magadan
Fiji Standard Time(UTC+12:00) Fiji
New Zealand Standard Time(UTC+12:00) Auckland, Wellington
Tonga Standard Time(UTC+13:00) Nuku’alofa

Modified from Wikipedia: