It wasn't until 1929 before most countries adopted hourly time zones. Time zones throughout the world vary, and used to vary even more than they currently do. Most commonly, UTC is offset by an hour, but in some cases, the offset can be a half-hour or quarter-hour, such as in the case of UTC+06:30 and UTC+12:45. UTC offset can range from UTC-12:00 to UTC+14:00. Generally, time zones are defined as + or - an integer number of hours in relation to UTC for example, UTC-05:00, UTC+08:00, and so on. UTC breaks time into days, hours, minutes, and seconds, where days are usually defined in terms of the Gregorian calendar. Most time zones that are on land are offset from UTC. UTC is not dependent on daylight saving time (DST), though some countries switch between time zones during their DST period, such as the United Kingdom using British Summer Time in the summer months. UTC, which is based on highly precise atomic clocks and the Earth's rotation, is the new standard of today. Although GMT used to be a time standard, it is now mainly used as the time zone for certain countries in Africa and Western Europe.
Although GMT and Coordinated Universal Time (UTC) essentially reflect the same time, GMT is a time zone, while UTC is a time standard that is used as a basis for civil time and time zones worldwide.
Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory located in Greenwich, London, considered to be located at a longitude of zero degrees. They are often based on the boundaries of countries or lines of longitude. Official time zone site of the U.S.A.Related Time Calculator | Date CalculatorĪ time zone is a region on Earth that uses a uniform time.The territories of the United States do not use Daylight Saving Time (DST). The USVI does not use Daylight Saving Time (DST)įederal district West Tennessee: Central Standard Time (CST)Įast Tennessee, except Marion County: Eastern Standard Time (EST)Įl Paso and Hudspeth Counties: Mountain Standard Time (MST) Western South Dakota: Mountain Standard Time (MST) Puerto Rico does not use Daylight Saving Time (DST)Įastern South Dakota: Central Standard Time (CST) Part of Malheur County: Mountain Standard Time (MST) The CNMI does not use Daylight Saving Time (DST) Western North Dakota: Mountain Standard Time (MST) West Wendover: Mountain Standard Time (MST) Most of the state: Pacific Standard Time (PST) Western part of the state: Mountain Standard Time (MST) Gogebic, Iron, Dickinson, and Menominee counties: Central Standard Time (CST) Western half of the state: Central Standard Time (CST)Įastern half of the state: Eastern Standard Time (EST) Greeley, Hamilton, Sherman and Wallace counties: Mountain Standard Time (MST) Most of the state: Central Standard Time (CST) Western part of the state: Central Standard Time (CST) North of the Salmon River: Pacific Standard Time (PST) Most of the state: Mountain Standard Time (MST) Hawaii does not use Daylight Saving Time (DST) Guam does not use Daylight Saving Time (DST) West of the Apalachicola River: Central Standard Time (CST) Most of the state: Eastern Standard Time (EST) The Navajo Nation uses Daylight Saving Time (DST), the rest of the state does notĪmerican Samoa does not use Daylight Saving Time (DST) Western Aleutian Islands: Hawaii–Aleutian Standard Time (HST) Most of the state: Alaska Standard Time (AKST) UTC-10: Hawaii-Aleutian Standard Time ( HAT).These are the times zones that are used by the United States and its territories:.For an explanation on what UTC+# and UTC-# mean, please see the UTC page. Note: the time zones listed on this page are listed in Coordinated Universal Time (UTC) as well as the names of the time zones as they are called within the United States. In the list, it will say if the state does not use DST. Most of the United States uses Daylight Saving Time (DST) in the summer. states (and the one federal district, Washington, D.C.) and territories showing their time zones.