Walter61: Fully improved the page.

2026-07-04T14:13:38Z

Fully improved the page.

← Older revision		Revision as of 10:13, 4 July 2026
Line 1:		Line 1:
	{{Short description\|~~Historical~~ time ~~standard associated with UTC+0~~}}		{{Short description\|Time standard based on mean solar time at Greenwich}}

	'''Greenwich Mean Time''' ('''GMT''') is a time standard ~~historically~~ based on mean solar time at the ~~Royal Observatory~~ in Greenwich, London. It ~~is associated with~~ the [[~~UTC+0~~]] ~~offset~~ and ~~is commonly used as a civil time reference in places that use no offset from~~ [[~~Coordinated Universal Time~~]].<ref name="utc-gmt"/><ref name="utc0-use"/>		'''Greenwich Mean Time''' ('''GMT''') is a time standard based on mean solar time at the Greenwich meridian in [[Greenwich]], [[London]]. It developed from astronomical observations made at the Royal Observatory in Greenwich. In ordinary civil use, GMT has the same clock reading as [[Coordinated Universal Time]] (UTC) and corresponds to the [[UTC+0]] offset.<ref name="utc-gmt"/><ref name="utc0-use"/>

	~~In modern timekeeping, [[Coordinated Universal Time]] is~~ the ~~main~~ reference ~~used~~ for ~~international~~ time~~-zone offsets~~. ~~GMT~~ remains ~~in use as a named~~ time ~~standard, especially~~ in ~~ordinary civil, geographic, and historical contexts~~.~~<ref name="time-zone-utc"/>~~		GMT served as the principal international reference for civil time from 1884 until UTC replaced it in 1972. It remains the standard time of the United Kingdom during the part of the year when daylight saving time is not in effect.

	== ~~Use~~ ==		== History ==
	~~Greenwich~~ Mean ~~Time~~ is ~~used as standard time in areas that follow UTC+0 during part or all~~ of the year. ~~It is most often associated with~~ the ~~United Kingdom and nearby Atlantic~~ and ~~western European timekeeping traditions~~.		Mean solar time is calculated by averaging the apparent movement of the Sun across the sky over the course of a year. This removes the daily variation found in apparent solar time and produces a consistent twenty-four-hour day.

	~~In countries that observe daylight saving~~ time, GMT ~~may be used during~~ the ~~standard-~~time ~~period before clocks move forward by one hour~~. ~~When daylight saving time is active,~~ the ~~local~~ time ~~may change~~ to a ~~UTC+1 offset~~.		The Royal Observatory was established at Greenwich in 1675. Astronomical observations made there allowed Greenwich mean solar time to be calculated and distributed. During the nineteenth century, Greenwich time became increasingly important as railways and telegraph networks required a common time instead of separate local times.

			The International Meridian Conference met in Washington, D.C., in 1884. The conference selected the Greenwich meridian as the international prime meridian. GMT subsequently became the main reference for international civil time and the calculation of time differences between locations.

			[[Coordinated Universal Time]] replaced GMT as the principal international civil time standard in 1972. GMT continued to be used as a named standard time and as a historical timekeeping term.

	== Relationship with UTC ==		== Relationship with UTC ==
	GMT and UTC~~+0 have~~ the ~~same clock reading in ordinary civil use~~. ~~When it~~ is ~~12:00 UTC, the local~~ time ~~under GMT is also 12:00~~.		GMT and UTC are technically different standards. GMT was historically determined through astronomical observations of the Earth's rotation and the mean position of the Sun. UTC is maintained through atomic timekeeping and is kept close to rotational time.<ref name="utc-gmt"/>

	UTC is the ~~modern technical standard~~ for ~~coordinated timekeeping~~. GMT ~~is used more often as a named civil time~~ and ~~historical reference~~.		Despite this difference, GMT and UTC normally have the same clock reading for civil purposes. A time of 12:00 UTC is therefore also 12:00 GMT. GMT applies no positive or negative offset and corresponds to UTC+00:00.

	== ~~Time calculation~~ ==		== Civil use ==
	~~Greenwich Mean~~ Time ~~applies no hour offset from~~ UTC. The ~~local~~ time ~~remains the same as Coordinated Universal Time~~.		The United Kingdom uses GMT as its standard time between the autumn and spring clock changes. When [[daylight saving time]] begins, clocks move forward by one hour and the country uses British Summer Time, which corresponds to [[UTC+1]]. The clocks return to GMT when daylight saving time ends.<ref name="dst-operation"/>

	~~For example, 08:00 UTC is 08:00~~ GMT. ~~23:00 UTC remains 23:00~~ GMT.		GMT itself does not move forward during the summer. The legal local time changes from GMT to British Summer Time and later returns to GMT.

	== See also ==		== See also ==
Line 29:		Line 33:
	== References ==		== References ==
	{{Reflist\|refs=		{{Reflist\|refs=
	<ref name="utc-gmt">"[[Coordinated Universal Time#Relationship to other time scales\|Relationship to other time scales]]". ''Coordinated Universal Time''. ''Vrienden Universe Wiki''~~. Section describing GMT as a historical time reference and UTC as the modern standard for most civil and technical use. Accessed 15 June 2026~~.</ref>		<ref name="utc-gmt">"[[Coordinated Universal Time#Relationship to other time scales\|Relationship to other time scales]]". ''Coordinated Universal Time''. ''Vrienden Universe Wiki''.</ref>
	<ref name="~~time~~-~~zone-utc~~">"[[~~Time zone~~#~~Relationship with UTC~~\|~~Relationship with UTC~~]]". ''~~Time zone~~''. ''Vrienden Universe Wiki''~~. Section describing UTC as the main reference point for time-zone offsets. Accessed 15 June 2026~~.</ref>		<ref name="utc0-use">"[[UTC+0#Use\|Use]]". ''UTC+0''. ''Vrienden Universe Wiki''.</ref>
	<ref name="~~utc0~~-~~use~~">"[[~~UTC+0~~#~~Use~~\|~~Use~~]]". ''~~UTC+0~~''. ''Vrienden Universe Wiki''~~. Section connecting UTC+0 with Greenwich Mean Time and Western European standard time. Accessed 15 June 2026~~.</ref>		<ref name="dst-operation">"[[Daylight saving time#Operation\|Operation]]". ''Daylight saving time''. ''Vrienden Universe Wiki''.</ref>
	}}		}}

			[[Category:Time standards]]
	[[Category:Time zones]]		[[Category:Time zones]]
	~~[[Category:UTC offsets]]~~

Walter61: Created page with "{{Short description|Historical time standard associated with UTC+0}} '''Greenwich Mean Time''' ('''GMT''') is a time standard historically based on mean solar time at the Royal Observatory in Greenwich, London. It is associated with the UTC+0 offset and is commonly used as a civil time reference in places that use no offset from Coordinated Universal Time. In modern timekeeping, Coordinated Universal Time is the ma..."

2026-06-15T12:38:50Z

Created page with "{{Short description|Historical time standard associated with UTC+0}} '''Greenwich Mean Time''' ('''GMT''') is a time standard historically based on mean solar time at the Royal Observatory in Greenwich, London. It is associated with the UTC+0 offset and is commonly used as a civil time reference in places that use no offset from Coordinated Universal Time.<ref name="utc-gmt"/><ref name="utc0-use"/> In modern timekeeping, Coordinated Universal Time is the ma..."

New page

{{Short description|Historical time standard associated with UTC+0}}

'''Greenwich Mean Time''' ('''GMT''') is a time standard historically based on mean solar time at the Royal Observatory in Greenwich, London. It is associated with the [[UTC+0]] offset and is commonly used as a civil time reference in places that use no offset from [[Coordinated Universal Time]].<ref name="utc-gmt"/><ref name="utc0-use"/>

In modern timekeeping, [[Coordinated Universal Time]] is the main reference used for international time-zone offsets. GMT remains in use as a named time standard, especially in ordinary civil, geographic, and historical contexts.<ref name="time-zone-utc"/>

== Use ==
Greenwich Mean Time is used as standard time in areas that follow UTC+0 during part or all of the year. It is most often associated with the United Kingdom and nearby Atlantic and western European timekeeping traditions.

In countries that observe daylight saving time, GMT may be used during the standard-time period before clocks move forward by one hour. When daylight saving time is active, the local time may change to a UTC+1 offset.

== Relationship with UTC ==
GMT and UTC+0 have the same clock reading in ordinary civil use. When it is 12:00 UTC, the local time under GMT is also 12:00.

UTC is the modern technical standard for coordinated timekeeping. GMT is used more often as a named civil time and historical reference.

== Time calculation ==
Greenwich Mean Time applies no hour offset from UTC. The local time remains the same as Coordinated Universal Time.

For example, 08:00 UTC is 08:00 GMT. 23:00 UTC remains 23:00 GMT.

== See also ==
* [[Coordinated Universal Time]]
* [[UTC+0]]
* [[UTC+1]]
* [[Time zone]]
* [[Daylight saving time]]

== References ==
{{Reflist|refs=
<ref name="utc-gmt">"[[Coordinated Universal Time#Relationship to other time scales|Relationship to other time scales]]". ''Coordinated Universal Time''. ''Vrienden Universe Wiki''. Section describing GMT as a historical time reference and UTC as the modern standard for most civil and technical use. Accessed 15 June 2026.</ref>
<ref name="time-zone-utc">"[[Time zone#Relationship with UTC|Relationship with UTC]]". ''Time zone''. ''Vrienden Universe Wiki''. Section describing UTC as the main reference point for time-zone offsets. Accessed 15 June 2026.</ref>
<ref name="utc0-use">"[[UTC+0#Use|Use]]". ''UTC+0''. ''Vrienden Universe Wiki''. Section connecting UTC+0 with Greenwich Mean Time and Western European standard time. Accessed 15 June 2026.</ref>
}}

[[Category:Time zones]]
[[Category:UTC offsets]]

Greenwich Mean Time - Revision history

Walter61: Fully improved the page.