![]() ![]() The acronym came about as a compromise between English and French speakers: Coordinated Universal Time would normally be abbreviated as CUT, and the French name, Temps Universel Coordonné, would be TUC. You might be wondering why UTC is the abbreviation for Coordinated Universal Time. UTC incorporates measurements of the Earth's rotation as well as averaged readings from around 400 atomic clocks around the world, according to the website. In 1967, a committee at the United Nations officially adopted UTC as a standard that's more accurate than GMT for setting clocks. Earthquakes, melting ice sheets and natural oscillations in our planet's motion can cause changes of a few fractions of a second in the amount of time it takes the Earth to spin on its axis, according to NASA. The time standard against which clocks were set then became known as Greenwich Mean Time (GMT).īut by the middle of the 20th century, the new technology of the atomic clock, which can measure time with incredible accuracy, was showing that the Earth's rotation actually varied slightly from day to day. At the conference, 41 delegates from 25 countries chose to set the prime meridian - the zero point for longitude lines - as passing through Greenwich, England, according to. But there was no universally agreed-upon equivalent for lines of longitude, which run north to south. Lines of latitude, which run east to west around our planet, had always been measured from the equator. Indiana introduced DST in 2006.In 1884, members met at the International Meridian Conference in Washington, D.C., to discuss a way to synchronize clocks around the globe. Most of Arizona and Hawaii don't use DST. In addition the uninhabited atolls of Baker Island (AoE) and Wake Island (WAKT) add to the time zone count, making 11 the total number of time zones in the US.Īlmost all states in the US use Daylight Saving Time (DST). There are 9 official time zones according to the law. The time zones in the law are defined by their offset from Coordinated Universal Time (UTC). Code, Title 15, Chapter 6, Subchapter IX - Standard Time. Time zones in the USA are defined in the U.S. Since 1967, the US Department of Transportation (DOT) has been responsible for governing time zones in the country. The US was divided into 4 standard time zones on November 18, 1883, and jurisdiction for the zones was given to the Interstate Commerce Commission (ICC). Time Zones Being Used in Dependencies of United States Offset They will become active again after the next clock change as Daylight Saving Time begins or ends. The above time zones are used during other parts of the year. Time Zones Not Currently Being Observed in United States Offset Note: Local time in these time zones changes when Daylight Saving Time begins and ends. In practice, this means that the local time in these time zones changes when DST begins and ends. For example, Eastern Time (ET) refers to Eastern Standard Time (EST) or Eastern Daylight Time (EDT), depending on which is currently in use. The time zones in the contiguous US are often referred to by their generic name, without making a difference between standard time and Daylight Saving Time designations. Generalized Time Zones in United States Time Zone Abbreviation & Name ![]() Since Howland Island and Baker Island constitute the world's westernmost landmasses in relation to the International Date Line, making them the last places on Earth where any date exists, they are sometimes assigned a theoretical 12th time zone called Anywhere on Earth (AoE). As neither Hawaii nor the 5 dependencies use Daylight Saving Time (DST), there are only 6 corresponding DST time zones. In addition, Alaska, Hawaii, and 5 US dependencies all have their own time zones. The contiguous US has 4 standard time zones. However, adding the time zones of 2 uninhabited US territories, Howland Island and Baker Island, brings the total count to 11 time zones. There are 9 time zones by law in the USA and its dependencies. Time Zones Currently Being Used in United States Offset Business Date to Date (exclude holidays). ![]()
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