for flight plans and air traffic control clearances. UTC is also the time standard used in aviation, e.g. For sub-microsecond precision, clients can obtain the time from satellite signals. If only milliseconds precision is needed, clients can obtain the current UTC from a number of official internet UTC servers. The Network Time Protocol (NTP), designed to synchronize the clocks of computers over the Internet, transmits time information from the UTC system.

UTC is used in many Internet and World Wide Web standards. Several jurisdictions have established time zones that differ by an odd integer number of half-hours or quarter-hours from UT1 or UTC.Ĭurrent civil time in a particular Time Zone can be determined by adding or subtracting the number of hours and minutes specified by the UTC offset, which ranges from UTC-12 in the west to UTC+14 in the east (see our interactive map for more details). 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.

Time Zones around the World are expressed using positive or negative offsets from UTC, as in the List of Time Zones by UTC offset. In some countries where English is spoken, the term Greenwich Mean Time (GMT) is often used as a synonym for UTC and predates UTC by nearly 300 years. It is within about 1 second of mean solar timeat Prime meridian, and is not adjusted for Daylight Saving Time. Today, Greenwich Mean Time (GMT) is only the name of a time zone that is used by a few countries in Africa and Western Europe, including the UK during winter and all year in Iceland.Coordinated Universal Time (abbreviated to UTC) is the primary time standard by which the world regulates clocks and time. Since then, GMT is no longer a time standard. Until 1972, Greenwich Mean Time (also known as Zulu time) was the same as Universal Time (UT). UTC was adjusted several times until 1972, when leap seconds were introduced to keep UTC in line with the Earth's rotation, which is not entirely even, and less exact than atomic clocks. The name Coordinated Universal Time was officially adopted in 1967. In 1960, the International Radio Consultative Committee formalized the concept of UTC, and it was put into practice the year after. The transit circle is a part of the telescope's mechanics and it is still cited as the prime meridian's original reference (0° longitude).

The reference line or starting point, the Prime Meridian, was determined to be the transit circle at the Royal Observatory in Greenwich, London. This is the basis for the 24-hour time zone system we know today.Īt the time, Greenwich Mean Time (GMT) was chosen as the world’s time standard. Universal Time (UT) was created at the International Meridian Conference in 1884. It is used to compare the pace provided by TAI with the actual length of a day on Earth.

Universal Time (UT1): Also known as astronomical time or solar time, it refers to the Earth's rotation.

International Atomic Time (TAI): A time scale that combines the output of some 400 highly precise atomic clocks worldwide, and provides the exact speed for our clocks to tick.

Two components are used to determine UTC: The world's timing centers have agreed to keep their time scales closely synchronized - or coordinated - therefore the name Coordinated Universal Time. UTC is the time standard commonly used across the world. ©/stocknshares A Standard, Not a Time Zone The Greenwich Meridian in London, England.

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