Difference Between GMT and UTC

GMT vs UTC
 

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.

Difference Between GMT and UTC

What is the difference between GMT and UTC?

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

• 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.

Images Courtesy: 

  1. Time by Alan Cleaver (CC BY 2.0)