Utc And Gmt Difference

Posted on  by admin

GMT vs UTC

Coordinated Universal Time (UTC) is used as the official world reference for time. Coordinated Universal Time replaced the use of Greenwich Mean Time (GMT) in 1972. You will often see time zones represented similar to UTC - 5h or GMT - 5h. Now, GMT is a time zone and UTC is a time standard. The time zones are represented as UTC – 2:00, UTC + 1:00 and so on. Read: Difference Between EST and MST: EST vs MST. Coordinated Universal Time or UTC is the primary time standard by which the world regulates clocks and time. It is within about 1 second of mean solar time at 0° longitude, and is not adjusted for daylight saving time. It is effectively a successor to Greenwich Mean Time (GMT).

When it comes to time keeping, one should know that the time difference between GMT and UTC is a fraction of a second and, for most common purposes, that difference is insignificant and considered as no difference. However, there are some other differences between GMT and UTC when it comes to usage. Before going into those differences, let us first see what GMT and UTC stand for. GMT is Greenwich Mean Time whereas UTC is Coordinated Universal Time. GMT refers to the time maintained at the Royal Observatory in Greenwich, London called the mean solar time. UTC is based on International Atomic Time (TAI).

What is GMT?

GMT, which stands for Greenwich Mean Time, is based on astronomical observations. GMT is a country based time standard. It is used primarily by bodies associated with the United Kingdom like the BBC World Service, the Royal Navy, and the Met Office. As a matter of fact, several countries adopt GMT in their legislation. They are the United Kingdom, Belgium, Republic of Ireland, and Canada.

What is UTC?

UTC, which stands for Coordinated Universal Time, is an international time scale recommended by the International Bureau of Weights and Measures (BIPM) as the legal basis for time. It is a method of measuring time using atomic clocks. To determine the international standard of Coordinated Universal Time, the Bureau of Weights and Measures (BIPM) in Paris Coordinates data from atomic clocks located in timing laboratories around the globe. It is interesting to note that leap seconds are added to UTC to compensate for the slowing rotation of the Earth. It is important to know that leap seconds are used to allow UTC to track the mean solar time in the Royal Observatory in Greenwich, London.

UTC is the time standard used for Internet and World Wide Web standards. It is also the basis of the satellite global positioning system (GPS). UTC is used by the Network Time Protocol, created to synchronize the clocks of many computers over the Internet. Thus, it can be said that the UTC is Internet based time standard.

The difference between Greenwich Mean Time and Coordinated Universal Time is measured in fractions of a second. In common use, when fractions of a second are considered not very important, GMT can be taken equivalent to UTC. The time difference is important, however, in scientific matters.

It is often thought that time zones around the world are positive or negative offsets from UTC. In fact, it is quite true that UTC replaced GMT as the main reference time scale in various regions.

Why it is called UTC? The International Telecommunication Union otherwise called ITU thought that it was best to have a single abbreviation for use in all the languages so that confusion can be curbed to a great extent. In fact, they could not arrive at a conclusion whether to have the English word order or the French word order and hence as a result the acronym UTC was chosen.

What is the difference between GMT and UTC?

• GMT stands for Greenwich Mean Time and UTC for Coordinated Universal Time.

Difference between gmt and utc time zone

Utc And Gmt Time Zone Difference

• Greenwich Mean Time is based on astronomical observations.

• Coordinated Universal Time (UTC) is an international time scale recommended by the International Bureau of Weights and Measures (BIPM) as the legal basis for time. It is a method of measuring time using atomic clocks.

• The time difference between UTC and GMT lies in fractions of a second. Therefore, for common purposes, both the times are considered the same. But, the time difference is important for scientific purposes.

• GMT is adopted in their legislations as in countries such as United Kingdom, Belgium, Republic of Ireland and Canada.

• UTC is the time standard used for several Internet and World Wide Web standards.

• It can be said that the UTC is Internet based time standard whereas GMT is country based time standard.

Gmt Time Zone Map

Images Courtesy:

  1. Time by Alan Cleaver (CC BY 2.0)

Related posts:

Greenwich Mean Time (GMT) This term originally refers to the mean solar time at the Royal Observatory in Greenwich, where a system of tracking time based on the rotation of the earth was developed around 1850. It is now often used to refer to Coordinated Universal Time (UTC) when it is considered a time zone.

Strictly speaking, UTC is not a time zone, but an atomic time scale that only approximates GMT in the old sense. It is also used to refer to Universal Time (UT), an astronomical concept that directly replaces the original GMT.

In 1970, the Coordinated Universal Time System was developed by an international advisory group of technical experts within the International Telecommunication Union (ITU). UTC is International Atomic Time (TAI, from the French Temps atomique international ) with leap seconds added at irregular intervals to compensate for the slow rotation of the earth. Jump seconds are used so that UTC can accurately track UT1, the mean solar time at the Royal Observatory, Greenwich.

The ITU found it best to establish a single abbreviation for use in all languages ​​to minimize confusion. Since no unanimous agreement could be reached on the use of the English word order, CUT ( coordinated world time ) or the French word sequence TUC ( temps universel coordonné ), the acronym UTC was chosen as a compromise.

The difference between UTC and UT1 must not exceed 0.9 s. If high accuracy is not required, the general term universal time (without a suffix) can be used.

In occasional operation, Greenwich Mean Time (GMT) corresponds to that of UTC and UT1. Because of the ambiguity of whether UTC or UT1 is meant, and because timekeeping laws normally refer to UTC, careful writing will avoid GMT.

Comparison table

Difference Between Utc And Gmt Java

GMT versus UTC comparison table

mean Greenwich Mean TimeUTC
Stands forGreenwich Mean TimeCoordinated Universal Time / Temps Universel Coordonné (abbreviation for neither English nor French)
Refers toA time zoneA system of timekeeping
UsageHuman readable clocksWith digitally synchronized clocks
Measured withRotation of the earth (historical)Atomic Transition Principle (periodic updates with astronomical time)

Time in Greenwich, UK

In Greenwich Township, GMT (in the form of UTC) is the official time in winter only (Greenwich summer time is UK daylight saving time, not 'GMT').

The Shepherd Gate clock at the Royal Observatory in Greenwich.

Time zones around the world

Difference Between Utc And Gmt

The video below shows a brief history of the time zones in the world, including the use and evolution of GMT and UTC. Cases of 'strange' time zones are also discussed, such as: B. Time zones that last half an hour and countries or regions that refuse to adopt traditional time zones.