GMT vs BST: Difference and Comparison

Both the term GMT and BST tell the time, but they have different meanings; it can also be said that they have very many similarities.

There is a straight one-hour difference between GMT and BST time zones, which results in a change in the time zone from UTC+00:00 to UTC+01:00. This time zone change affects the daylight, for instance, mornings have 1 hour’s less daylight, and on the other hand, evenings have 1 hour more. 

Like other time zones, GMT is recorded as per the mean solar time, but it is specifically for the Royal Observatory of Greenwich, London.

Another considerable thing is that this time standard remains the same for all years and isn’t affected by summertime clock changes. This time zone is the standard in Europe, Antarctica, Africa, and North America.

Key Takeaways

  1. GMT is Greenwich Mean Time, a time standard based on the Prime Meridian at the Royal Observatory in Greenwich, London.
  2. BST stands for British Summer Time, the United Kingdom’s daylight saving time observed during summer.
  3. The UK switches from GMT to BST by advancing the clock one hour ahead in March and reverts to GMT by setting the clock one hour back in October.


GMT stands for Greenwich Mean Time, the time zone based on the mean solar time at the Royal Observatory in Greenwich, London, UK. It is used as a reference time for time zones worldwide. BST stands for British Summer Time, the daylight saving time used in the United Kingdom. It is observed during the summer months. 


Comparison Table

Parameter of ComparisonGMTBST
DefinitionBST, or British Summer Time, stands for the mean solar time, which affects the daylight by an hour difference compared to GMT in the United Kingdom between March and October.GMT, or Greenwich Mean Time, represents the mean solar time, which the Royal Observatory of Greenwich London records.
OriginThe British summertime act was created in 1972, which led to the clocks changing from March to late October.The GMT was 1st introduced or came into play in November 1884 at the International Meridian Conference in Washington, DC, USA.
PracticesBritish mariners have used GMT since the early 1800.BST was introduced in the early 1900.
DurationGMT starts on the last day following BST.BST starts on the last day of Sunday of March and ends on the last Sunday of October.
ImportanceGMT is considered the reference at the prime meridian at Greenwich; therefore, it becomes the Centre of world time and for the global system of time zones.BST was introduced temporarily when ordinary daylight saving would be in action.

What is GMT?

GMT, or Greenwich Mean Time, is the time introduced at midnight at Royal Observatory in Greenwich, London. IT started in the early 1800 when transportation and communication were developing; the coordination of different areas was a real mesh.

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For example, if there was noon in any place in the west, whereas in the south, the afternoon was almost over, it created many problems among the USA railway officers and the officers working on expanding the railway run.

So, to face the situation, the standard system was recommended in 1883.

Some intellects also propose that the GMT concept was introduced in 1884 when 26 countries held a meeting and concluded that the royal observatory in Greenwich, London, would be the reference point for 0-degree longitude.

The above concepts suggest the same theory that the globe is divided into 24 time zones. According to theory, our earth completes one rotation in its axis in 24 hours which equals 360 degrees in 1 rotation.

Further 360/15=24 time zones. From the North Pole to the South Pole, 24 lines were drawn at an interval of 15 degrees each.

So, the earth moves 15 degrees in an hour. Therefore, whenever we move 15-degree 1 hour will be changed, and it depends upon whether it increases by 1 hour or decreases by 1 hour depending upon.

If you move left to the prime meridian, the time will decrease by an hour; if you move right, it will increase by one hour.

What is BST?

BST, or British Summer Time, was known quite a few years ago but was considered in the middle of the first world war in 1916. William Willet introduced it, but most people don’t know its significance, and it’s like the sun is going to set and rise as usual, but why is it important to have BST?

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British Summer Time is also known as daylight saving time, and in Britain, the sunlight is less in winter than in summer. The daylight is taken between the sunrise, which is 8’ o’clock in the morning, and the sunset is 4’o clock evening giving us less daylight time.

While in summer, the sunlight is more because the sunrise is at 3:30 A.M. and the sunset is 8:30 P.M., which causes extra daylight. Therefore, during summer in Britain, the morning is extended by 1 hour, from 3:30 to 4:30, and the evening is increased by an hour, which is 8:30 to 9:30.

Therefore, this increase in an hour gives the citizen the advantage of having one hour ahead of the usual time.

Main Differences Between GMT and BST

  1. The first noticeable difference is hidden in the name, Where GMT stands for Greenwich Mean Time; on the other hand, BST stands for British Summertime.
  2. Both are related to the time system and give an idea of the different time zones in different areas.
  3. GMT is the standard time system, while BST is followed in Britain in the summertime.
  4. GMT and BST were founded in the United Kingdom; GMT is followed in winter, and BST is followed in summer.
  5. GMT is somewhat similar to coordinated universal time; in GMT, the earth is divided into 24 different parts, while in BST, there is no such thing; it is as simple as it’s GMT +1 hour.
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Last Updated : 11 June, 2023

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