| Current: | GMT — Greenwich Mean Time |
|---|---|
| Next Change: | BST — British Summer Time |
| Current Offset: | No UTC/GMT offset |
| Difference: | 9 hours behind Tokyo |
1916 Time Zones - London
The graph above illustrates clock changes in London during 1916.
London in GMT Time Zone
London uses Greenwich Mean Time (GMT) during standard time and British Summer Time (BST) during Daylight Saving Time (DST), or summer time.
The Difference between GMT and UTC
In practice, GMT and UTC share the same time on a clock, which can cause them to be interchanged or confused. However, there is an essential difference between the two:
- UTC is a time standard that forms the base of time zones worldwide and is not used as a time zone in any country. Time zones are defined by their offsets from UTC. Since GMT has a UTC offset of zero, there is no time difference between the two.
- GMT is a time zone used in the UK and other European and African countries.
A source of confusion is that GMT used to be the world's time standard before UTC was introduced. Until 1972, time zones were defined by their offset from GMT based on mean solar time at the prime meridian in Greenwich near London.
What About BST?
During Daylight Saving Time, clocks in the United Kingdom are set forward one hour to British Summer Time (BST). The UK is the only country that observes BST in the summer. Some other countries, such as Ireland, observe the same local time, but under a different name.
Time Changes in London Over the Years
Daylight Saving Time (DST) changes do not necessarily occur on the same date every year.
| Year | Date & Time | Abbreviation | Time Change | Offset After |
|---|---|---|---|---|
| 1900 — 1915 | No changes, UTC all of the period | |||
| 1916 | 5月21日 (日)2時00分 | GMT → BST | +1 hour (DST start) | UTC+1h |
| 10月1日 (日)3時00分 | BST → GMT | -1 hour (DST end) | UTC | |
| 1917 | 4月8日 (日)2時00分 | GMT → BST | +1 hour (DST start) | UTC+1h |
| 9月17日 (月)3時00分 | BST → GMT | -1 hour (DST end) | UTC | |
| 1918 | 3月24日 (日)2時00分 | GMT → BST | +1 hour (DST start) | UTC+1h |
| 9月30日 (月)3時00分 | BST → GMT | -1 hour (DST end) | UTC | |
| 1919 | 3月30日 (日)2時00分 | GMT → BST | +1 hour (DST start) | UTC+1h |
| 9月29日 (月)3時00分 | BST → GMT | -1 hour (DST end) | UTC | |
| 1920 | 3月28日 (日)2時00分 | GMT → BST | +1 hour (DST start) | UTC+1h |
| 10月25日 (月)3時00分 | BST → GMT | -1 hour (DST end) | UTC | |
| 1921 | 4月3日 (日)2時00分 | GMT → BST | +1 hour (DST start) | UTC+1h |
| 10月3日 (月)3時00分 | BST → GMT | -1 hour (DST end) | UTC | |
| 1922 | 3月26日 (日)2時00分 | GMT → BST | +1 hour (DST start) | UTC+1h |
| 10月8日 (日)3時00分 | BST → GMT | -1 hour (DST end) | UTC | |
| 1923 | 4月22日 (日)2時00分 | GMT → BST | +1 hour (DST start) | UTC+1h |
| 9月16日 (日)3時00分 | BST → GMT | -1 hour (DST end) | UTC | |
| 1924 | 4月13日 (日)2時00分 | GMT → BST | +1 hour (DST start) | UTC+1h |
| 9月21日 (日)3時00分 | BST → GMT | -1 hour (DST end) | UTC | |
| * All times are local London time. | ||||
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