|Light Blue||Western European Time / Greenwich Mean Time (UTC)|
|Blue||Western European Time / Greenwich Mean Time (UTC)|
|Western European Summer Time / British Summer Time / Irish Standard Time (UTC+1)|
|Red||Central European Time (UTC+1)|
|Central European Summer Time (UTC+2)|
|Yellow||Eastern European Time / Kaliningrad Time (UTC+2)|
|Ochre||Eastern European Time (UTC+2)|
|Eastern European Summer Time (UTC+3)|
|Green||Moscow Time / Turkey Time (UTC+3)|
|Turquoise||Armenia Time / Azerbaijan Time / Georgia Time / Samara Time (UTC+4)|
The United Kingdom uses Greenwich Mean Time or Western European Time (UTC) and British Summer Time or Western European Summer Time (UTC+01:00).
Until the advent of the railways, the United Kingdom used local mean time. Greenwich Mean Time was adopted first by the Great Western Railway in 1840 and a few others followed suit in the following years. In 1847 it was adopted by the Railway Clearing House, and by almost all railway companies by the following year. It was from this initiative that the term "railway time" was derived.
|Statutes (Definition of Time) Act 1880|
|Act of Parliament|
|Long title||An Act to remove doubts as to the meaning of Expressions relative to Time occurring in Acts of Parliament, deeds, and other legal instruments.|
|Citation||43 & 44 Vict. c. 9|
|Royal assent||2 August 1880|
|Commencement||2 August 1880|
|Repealed||1 January 1979|
|Repealed by||Interpretation Act 1978|
It was gradually adopted for other purposes, but the legal case of Curtis v March in 1858 held "local mean time" to be the official time.On 14 May 1880, a letter signed by 'Clerk to Justices' appeared in The Times, stating that 'Greenwich time is now kept almost throughout England, but it appears that Greenwich time is not legal time. This was changed later in 1880, when Greenwich Mean Time was legally adopted throughout the island of Great Britain under the Statutes (Definition of Time) Act 1880 (43 & 44 Vict. c. 9). GMT was adopted on the Isle of Man on 30 March 1883, Jersey in 1898, and Guernsey in 1913. Ireland adopted GMT in 1916, supplanting Dublin Mean Time.
|Summer Time Act 1916|
|Act of Parliament|
|Citation||6 & 7 Geo. 5. c. 14|
|Summer Time Act 1922|
|Act of Parliament|
|Long title||An Act to provide for the time in Great Britain, Northern Ireland, the Channel Islands, and the Isle of Man being in advance of Greenwich mean time during a certain period of the year.|
|Citation||12 & 13 Geo. 5. c. 22|
|Royal assent||20 July 1922|
|Repealed by||Summer Time Act 1972|
Daylight saving time was introduced by the Summer Time Act 1916 (6 & 7 Geo. 5. c. 14), which was implemented in 1916 as GMT plus one hour and Dublin Mean Time plus one hour. The length of DST could be extended by Order in Council, and was extended for the duration of World War I. For 1916, DST extended from 21 May to 1 October, with transitions at 02:00 standard time. On 1 October 1916, Greenwich Mean Time was introduced to Ireland.
At the beginning of the 20th century, Sandringham Time (UTC+00:30) was used by the royal household. This practice was abolished by King Edward VIII in an effort to reduce confusions over time.
|Summer Time Act 1947|
|Act of Parliament|
|Long title||An Act to amend the Summer Time Acts, 1922 and 1925.|
|Citation||10 & 11 Geo. 6. c. 16|
|Royal assent||11 March 1947|
|Repealed by||Summer Time Act 1972|
In the summers of 1941 to 1945, during the Second World War, Britain was two hours ahead of GMT and operating on British Double Summer Time (BDST). To bring this about, the clocks were not put back by an hour at the end of summer in 1940 (BST having started early, on 25 February 1940). In subsequent years, clocks continued to be advanced by one hour each spring (to BDST) and put back by an hour each autumn (to BST). On 15 July 1945, the clocks were put back by an hour, so BDST reverted to BST; the clocks were put back by an additional hour on 7 October 1945, so BST reverted to GMT for the winter of 1945.
The United Kingdom experimentally adopted Central European Time by maintaining Summer Time throughout the year from 1968 to 1971.In a House of Lords debate, Richard Butler, 17th Viscount Mountgarret said that the change was welcomed at the time, but the experiment was eventually halted after a debate in 1971, in which the outcome might have been influenced by a major accident on the morning of the debate. Proposals to adopt CET have been raised by various politicians over the years, including a proposal in 2011 to conduct an analysis of the costs and benefits.
|Summer Time Act 1972|
|Act of Parliament|
|Long title||An Act to consolidate the enactments relating to summer time.|
|Citation||1972 c. 6|
|Royal assent||10 February 1972|
|Commencement||10 March 1972|
|Text of the Summer Time Act 1972 as in force today (including any amendments) within the United Kingdom, from legislation.gov.uk.|
The dates of British Summer Time are the subject of the Summer Time Act 1972. From 1972 to 1980, the day following the third Saturday in March was the start of British Summer Time (unless that day was Easter Sunday, in which case BST began a week earlier), with the day following the fourth Sunday in October being the end of British Summer Time. From 1981 to 2001, the dates were set in line with various European Directives. Since 2002 the Act has specified the last Sunday in March as the start of British Summer Time with the last Sunday in October being end of British Summer Time.
Since 1998 the start and end date are the same in both the United Kingdom and the European Union.
A proposal to repeal European Directive 2000/84/EC and require that member states observe their own choice of time year-round was initiated in September 2018. As of September 2018 [update] , the UK Government had "no plans" to end daylight saving.The United Kingdom left the EU before this reform became effective; the UK is subsequently free to make its own arrangements.
In July 2019, the House of Lords EU Internal Market Sub-Committee launched a new inquiry into the implications for the UK of the European changes, to "explore what preparations the Government needs to make and what factors should inform the UK's response."
Authority over the time zone in Northern Ireland can be legislated by the Northern Ireland Assemblybut the power has never been used, as the Republic has followed the UK. In Scotland and Wales, time zone is a reserved matter, meaning that only the Parliament of the United Kingdom has power to legislate.
The IANA time zone database contains one zone for the United Kingdom in the file zone.tab, named Europe/London. This refers to the area having the ISO 3166-1 alpha-2 country code "GB". The zone names Europe/Guernsey, Europe/Isle_of_Man and Europe/Jersey exist because they have their own ISO 3166-1 alpha-2 but the zone.tab entries are links to Europe/London. There are several entries for UK possessions around the world.
Data directly from zone.tab of the IANA time zone database. Columns marked with * are the columns from zone.tab itself.
|c.c.*||Coordinates*||TZ*||Comments*||UTC offset||UTC DST offset|
|Standard time||Summer time|
|UTC−04:00 (AST, DST never observed)||Anguilla, British Virgin Islands, Montserrat, Turks and Caicos Islands|
|UTC−03:00 (FKST)||Falkland Islands|
|UTC−02:00||South Georgia and the South Sandwich Islands|
|UTC (GMT)||UTC+01:00||United Kingdom (England, Northern Ireland, Scotland, and Wales), Guernsey, Isle of Man, Jersey|
|UTC (GMT, DST never observed)||Saint Helena, Ascension and Tristan da Cunha|
|UTC+02:00 (EET)||UTC+03:00||Akrotiri and Dhekelia|
|UTC+06:00||British Indian Ocean Territory|
Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, counted from midnight. At different times in the past, it has been calculated in different ways, including being calculated from noon; as a consequence, it cannot be used to specify a particular time unless a context is given. The term 'GMT' is also used as one of the names for the time zone UTC+00:00 and, in UK law, is the basis for civil time in the United Kingdom.
A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.
Universal Time is a time standard based on Earth's rotation. While originally it was mean solar time at 0° longitude, precise measurements of the Sun are difficult. Therefore, UT1 is computed from a measure of the Earth's angle with respect to the International Celestial Reference Frame (ICRF), called the Earth Rotation Angle. UT1 is the same everywhere on Earth. UT1 is required to follow the relationship
Western European Summer Time is a summer daylight saving time scheme, 1 hour ahead of Greenwich Mean Time and Coordinated Universal Time. It is used in:
Central European Time (CET) is a standard time of Central, and parts of Western Europe, which is one hour ahead of Coordinated Universal Time (UTC). The time offset from UTC can be written as UTC+01:00. It is used in most parts of Europe and in a few North African countries. CET is also known as Middle European Time and by colloquial names such as Amsterdam Time, Berlin Time, Brussels Time, Madrid Time, Paris Time, Rome Time, Prague time,Warsaw Time or Romance Standard Time (RST).
Western European Time is a time zone covering parts of western Europe and consists of countries using UTC±00:00. It is one of the three standard time zones in the European Union along with Central European Time and Eastern European Time.
Standard time is the synchronization of clocks within a geographical region to a single time standard, rather than a local mean time standard. Generally, standard time agrees with the local mean time at some meridian that passes through the region, often near the centre of the region. Historically, standard time was established during the 19th century to aid weather forecasting and train travel. Applied globally in the 20th century, the geographical regions became time zones. The standard time in each time zone has come to be defined as an offset from Universal Time. A further offset is applied for part of the year in regions with daylight saving time.
Summer time in Europe is the variation of standard clock time that is applied in most European countries in the period between spring and autumn, during which clocks are advanced by one hour from the time observed in the rest of the year, with a view to making the most efficient use of seasonal daylight. It corresponds to the notion and practice of daylight saving time (DST) to be found in some other parts of the world.
During British Summer Time (BST), civil time in the United Kingdom is advanced one hour forward of Greenwich Mean Time (GMT), in effect changing the time zone from UTC±00:00 to UTC+01:00, so that mornings have one hour less daylight, and evenings one hour more.
Canada is divided into six time zones. Most areas of the country's provinces and territories operate on standard time from the first Sunday in November to the second Sunday in March and daylight saving time the rest of the year.
Malaysian Standard Time or Malaysian Time (MYT) is the standard time used in Malaysia. It is 8 hours ahead of Coordinated Universal Time (UTC). Malaysia does not observe daylight saving time.
UTC+00:00 is an identifier for a time offset from UTC of +00:00. This time zone is the basis of UTC and all other time zones are based on it. In ISO 8601, an example of the associated time would be written as 2023-01-01T12:12:34+00:00. It is also known by the following geographical or historical names:
UTC−00:25:21 is an identifier for a time offset from UTC of −00:25:21, i.e. twenty-five minutes and twenty-one seconds behind Greenwich Mean Time. This time was used in Ireland between 1880 and 1916.
Railway time was the standardised time arrangement first applied by the Great Western Railway in England in November 1840, the first recorded occasion when different local mean times were synchronised and a single standard time applied. The key goals behind introducing railway time were to overcome the confusion caused by having non-uniform local times in each town and station stop along the expanding railway network and to reduce the incidence of accidents and near misses, which were becoming more frequent as the number of train journeys increased.
Myanmar Standard Time, formerly Burma Standard Time (BST), is the standard time in Myanmar, 6.5 hours ahead of UTC. Myanmar Standard Time is calculated on the basis of 97°30′E longitude. Myanmar Standard Time is used all year round, as Myanmar does not observe daylight saving time.
Metropolitan France uses Central European Time as its standard time, and observes Central European Summer Time from the last Sunday in March to the last Sunday in October. With its overseas territories, France uses 12 different time zones, more than any other country in the world.
Ireland uses Irish Standard Time in the summer months and Greenwich Mean Time in the winter period.
Denmark, including the dependencies Faroe Islands and Greenland, uses six time zones.
Time in the Kingdom of the Netherlands is denoted by Central European Time (CET) during the winter as standard time in the Netherlands, which is one hour ahead of coordinated universal time (UTC+01:00), and Central European Summer Time (CEST) during the summer as daylight saving time, which is two hours ahead of coordinated universal time (UTC+02:00). The Caribbean Netherlands – which consist of the islands of Bonaire, Sint Eustatius and Saba – all observe Atlantic Standard Time (AST) year-round, which is four hours behind coordinated universal time (UTC−04:00).
Finland uses Eastern European Time (EET) during the winter as standard time and Eastern European Summer Time (EEST) during the summer as daylight saving time. EET is two hours ahead of coordinated universal time (UTC+02:00) and EEST is three hours ahead of coordinated universal time (UTC+03:00). Finland adopted EET on 30 April 1921, and has observed daylight saving time in its current alignment since 1981 by advancing the clock forward one hour at 03:00 EET on the last Sunday in March and back at 04:00 EET on the last Sunday in October, doing so an hour earlier for the first two years.