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{{Short description|Primary time standard}} | {{Short description|Primary time standard}} | ||
{{Redirect|UTC | {{Redirect|UTC|the time zone that lies between UTC−1 and UTC+1|UTC±00:00|other uses}} | ||
{{Pp-move-indef|t=t}} | {{Pp-move-indef|t=t}} | ||
{{Use dmy dates|date=September 2020}} | {{Use dmy dates|date=September 2020}} | ||
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Since 1972, UTC is calculated by subtracting the accumulated leap seconds from [[International Atomic Time]] (TAI), which is a [[coordinate time]] scale tracking notional [[proper time]] on the rotating surface of the [[Earth]] (the [[geoid]]). In order to maintain a close approximation to [[Universal Time|UT1]], UTC occasionally has [[Classification of discontinuities|discontinuities]] where it changes from one linear function of TAI to another. These discontinuities take the form of leap seconds implemented by a UTC day of irregular length. Discontinuities in UTC have occurred only at the end of June or December, although there is provision for them to happen at the end of March and September as well as a second preference.{{sfn|History of TAI-UTC|c. 2009}}{{sfn|McCarthy|Seidelmann|2009|pp=217, 227–231}} The International Earth Rotation and Reference Systems Service (IERS) tracks and publishes the difference between UTC and Universal Time, [[DUT1]] = UT1 − UTC, and introduces discontinuities into UTC to keep DUT1 in the [[interval (mathematics)|interval]] (−0.9 s, +0.9 s). | Since 1972, UTC is calculated by subtracting the accumulated leap seconds from [[International Atomic Time]] (TAI), which is a [[coordinate time]] scale tracking notional [[proper time]] on the rotating surface of the [[Earth]] (the [[geoid]]). In order to maintain a close approximation to [[Universal Time|UT1]], UTC occasionally has [[Classification of discontinuities|discontinuities]] where it changes from one linear function of TAI to another. These discontinuities take the form of leap seconds implemented by a UTC day of irregular length. Discontinuities in UTC have occurred only at the end of June or December, although there is provision for them to happen at the end of March and September as well as a second preference.{{sfn|History of TAI-UTC|c. 2009}}{{sfn|McCarthy|Seidelmann|2009|pp=217, 227–231}} The International Earth Rotation and Reference Systems Service (IERS) tracks and publishes the difference between UTC and Universal Time, [[DUT1]] = UT1 − UTC, and introduces discontinuities into UTC to keep DUT1 in the [[interval (mathematics)|interval]] (−0.9 s, +0.9 s). | ||
As with TAI, UTC is only known with the highest precision in retrospect. Users who require an approximation in real time must obtain it from a time laboratory, which disseminates an approximation using techniques such as [[GPS]] or radio [[time signal]]s. Such approximations are designated UTC(''k''), where ''k'' is an abbreviation for the time laboratory.{{sfn|McCarthy|Seidelmann|2009|p=209}} The time of events may be provisionally recorded against one of these approximations; later corrections may be applied using the [[International Bureau of Weights and Measures]] (BIPM) monthly publication of tables of differences between canonical TAI/UTC and TAI(''k'')/UTC(''k'') as estimated in real time by participating laboratories.{{ | As with TAI, UTC is only known with the highest precision in retrospect. Users who require an approximation in real time must obtain it from a time laboratory, which disseminates an approximation using techniques such as [[GPS]] or radio [[time signal]]s. Such approximations are designated UTC(''k''), where ''k'' is an abbreviation for the time laboratory.{{sfn|McCarthy|Seidelmann|2009|p=209}} The time of events may be provisionally recorded against one of these approximations; later corrections may be applied using the [[International Bureau of Weights and Measures]] (BIPM) monthly publication of tables of differences between canonical TAI/UTC and TAI(''k'')/UTC(''k'') as estimated in real time by participating laboratories.<ref>{{cite web|url=https://www.bipm.org/en/time-ftp/circular-t|title=Circular T|website=[[International Bureau of Weights and Measures]]}}</ref> (See the article on [[International Atomic Time]] for details.) | ||
Because of [[time dilation]], a standard clock not on the geoid, or in rapid motion, will not maintain synchronicity with UTC. Therefore, [[telemetry]] from clocks with a known relation to the geoid is used to provide UTC when required, on locations such as those of spacecraft. | Because of [[time dilation]], a standard clock not on the geoid, or in rapid motion, will not maintain synchronicity with UTC. Therefore, [[telemetry]] from clocks with a known relation to the geoid is used to provide UTC when required, on locations such as those of spacecraft. | ||
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The time zone using UTC is sometimes denoted [[UTC±00:00]] or by the letter ''Z''—a reference to the equivalent [[Nautical time|nautical time zone]] (GMT), which has been denoted by a ''Z'' since about 1950. Time zones were identified by successive letters of the alphabet and the Greenwich time zone was marked by a ''Z'' as it was the point of origin. The letter also refers to the "zone description" of zero hours, which has been used since 1920 (see [[time zone#History|time zone history]]). Since the [[NATO phonetic alphabet]] word for ''Z'' is "Zulu", UTC is sometimes known as "Zulu time". This is especially true in aviation, where "Zulu" is the universal standard.{{sfn | Military & Civilian Time Designations | n.d.}} This ensures that all pilots, regardless of location, are using the same [[24-hour clock]], thus avoiding confusion when flying between time zones.{{sfn | Williams | 2005}} See the [[list of military time zones]] for letters used in addition to ''Z'' in qualifying time zones other than Greenwich. | The time zone using UTC is sometimes denoted [[UTC±00:00]] or by the letter ''Z''—a reference to the equivalent [[Nautical time|nautical time zone]] (GMT), which has been denoted by a ''Z'' since about 1950. Time zones were identified by successive letters of the alphabet and the Greenwich time zone was marked by a ''Z'' as it was the point of origin. The letter also refers to the "zone description" of zero hours, which has been used since 1920 (see [[time zone#History|time zone history]]). Since the [[NATO phonetic alphabet]] word for ''Z'' is "Zulu", UTC is sometimes known as "Zulu time". This is especially true in aviation, where "Zulu" is the universal standard.{{sfn | Military & Civilian Time Designations | n.d.}} This ensures that all pilots, regardless of location, are using the same [[24-hour clock]], thus avoiding confusion when flying between time zones.{{sfn | Williams | 2005}} See the [[list of military time zones]] for letters used in addition to ''Z'' in qualifying time zones other than Greenwich. | ||
On electronic devices which only allow the time zone to be configured using maps or city names, UTC can be selected indirectly by selecting cities such as [[Accra]] in [[Ghana]] or [[Reykjavík]] in [[Iceland]] as they are always on UTC and do not currently use [[Daylight Saving Time]].{{sfn|Iceland|2011}} | On electronic devices which only allow the time zone to be configured using maps or city names, UTC can be selected indirectly by selecting cities such as [[Accra]] in [[Ghana]] or [[Reykjavík]] in [[Iceland]] as they are always on UTC and do not currently use [[Daylight Saving Time]] (which [[Greenwich]] and [[London]] do, and so could be a source of error).{{sfn|Iceland|2011}} | ||
===Daylight saving time=== | ===Daylight saving time=== | ||
{{Main|Daylight saving time}} | {{Main|Daylight saving time}} | ||
UTC does not change with a change of seasons, but [[Time zone|local time]] or civil time may change if a time zone jurisdiction observes daylight saving time (summer time). For example, local time on the east coast of the United States is five hours behind UTC during winter, but four hours behind while daylight saving is observed there.{{sfn| | UTC does not change with a change of seasons, but [[Time zone|local time]] or civil time may change if a time zone jurisdiction observes daylight saving time (summer time). For example, local time on the east coast of the United States is five hours behind UTC during winter,{{sfn|15 U.S. Code § 261|2007}} but four hours behind while daylight saving is observed there.{{sfn|15 U.S. Code § 260a|2005}} | ||
==History== | ==History== | ||
{{Further|Universal time#History}} | |||
In 1928, the term Universal Time (UT) was introduced by the International Astronomical Union to refer to GMT, with the day starting at midnight.{{sfn|McCarthy|Seidelmann|2009|pp=10–11}} Until the 1950s, broadcast [[time signal]]s were based on UT, and hence on the rotation of the Earth. | |||
In 1955, the [[caesium]] [[atomic clock]] was invented. This provided a form of timekeeping that was both more stable and more convenient than astronomical observations. In 1956, the U.S. [[National Bureau of Standards]] and [[U.S. Naval Observatory]] started to develop atomic frequency time scales; by 1959, these time scales were used in generating the [[WWV (radio station)|WWV]] time signals, named for the shortwave radio station that broadcasts them. In 1960, the U.S. Naval Observatory, the Royal Greenwich Observatory, and the [[National Physical Laboratory (United Kingdom)|UK National Physical Laboratory]] coordinated their radio broadcasts so that time steps and frequency changes were coordinated, and the resulting time scale was informally referred to as "Coordinated Universal Time".{{sfn|McCarthy|Seidelmann|2009|pp=226–227}}{{sfn|McCarthy |2009|p=3}} | In 1955, the [[caesium]] [[atomic clock]] was invented. This provided a form of timekeeping that was both more stable and more convenient than astronomical observations. In 1956, the U.S. [[National Bureau of Standards]] and [[U.S. Naval Observatory]] started to develop atomic frequency time scales; by 1959, these time scales were used in generating the [[WWV (radio station)|WWV]] time signals, named for the shortwave radio station that broadcasts them. In 1960, the U.S. Naval Observatory, the Royal Greenwich Observatory, and the [[National Physical Laboratory (United Kingdom)|UK National Physical Laboratory]] coordinated their radio broadcasts so that time steps and frequency changes were coordinated, and the resulting time scale was informally referred to as "Coordinated Universal Time".{{sfn|McCarthy|Seidelmann|2009|pp=226–227}}{{sfn|McCarthy |2009|p=3}} | ||
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==Future== | ==Future== | ||
{{See also|Leap second}} | {{See also|Leap second}} | ||
As the Earth's rotation continues to slow, positive leap seconds will be required more frequently. The long-term [[derivative|rate of change]] of LOD is approximately +1.7 ms per century. At the end of the 21st century, LOD will be roughly 86,400.004 s, requiring leap seconds every 250 days. Over several centuries, the frequency of leap seconds will become problematic.{{sfn|McCarthy|Seidelmann|2009|p=232}} A change in the trend of the UT1 - UTC values was seen beginning around June 2019 where the instead trending negative (with leap seconds to keep the difference between UT1 and UTC less than 0.9 seconds. The earth rotation has sped up, causing this difference to increase. If the trend continues, a negative leap second may be required, which has not been used before. This may not be needed until 2025.<ref>{{Cite | As the Earth's rotation continues to slow, positive leap seconds will be required more frequently. The long-term [[derivative|rate of change]] of LOD is approximately +1.7 ms per century. At the end of the 21st century, LOD will be roughly 86,400.004 s, requiring leap seconds every 250 days. Over several centuries, the frequency of leap seconds will become problematic.{{sfn|McCarthy|Seidelmann|2009|p=232}} A change in the trend of the UT1 - UTC values was seen beginning around June 2019 where the instead trending negative (with leap seconds to keep the difference between UT1 and UTC less than 0.9 seconds. The earth rotation has sped up, causing this difference to increase. If the trend continues, a negative leap second may be required, which has not been used before. This may not be needed until 2025.<ref>{{Cite press release|date=10 February 2021|title=Are Negative Leap Seconds in Our Future?|url=https://www.cnmoc.usff.navy.mil/Portals/49/Leap%20Second%20press%20releasedmcngs.pdf|access-date=18 June 2022|publisher=US Naval Observatory}}</ref><ref>{{Cite web|date=16 September 2021|title=Plots for UT1-UTC - Bulletin A All|url=https://datacenter.iers.org/singlePlot.php?plotname=BulletinA_All-UT1-UTC&id=6|access-date=16 September 2021|website=International Earth Rotation and Reference Systems Service}}</ref> | ||
Some time in the 22nd century, two leap seconds will be required every year. The current use of only the leap second opportunities in June and December will be insufficient to maintain a difference of less than 1 second, and it might be decided to introduce leap seconds in March and September. In the 25th century, four leap seconds are projected to be required every year, so the current quarterly options would be insufficient. | Some time in the 22nd century, two leap seconds will be required every year. The current use of only the leap second opportunities in June and December will be insufficient to maintain a difference of less than 1 second, and it might be decided to introduce leap seconds in March and September. In the 25th century, four leap seconds are projected to be required every year, so the current quarterly options would be insufficient. | ||
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There is a proposal to redefine UTC and abolish leap seconds, so that [[sundial]]s would very slowly get further out of sync with civil time.{{sfn | Allen | 2011b}} The resulting gradual shift of the sun's movements relative to civil time is analogous to the shift of [[season]]s relative to the yearly calendar that results from the calendar year not precisely matching the [[tropical year]] length. This would be a practical change in civil timekeeping, but would take effect slowly over several centuries. UTC (and TAI) would be more and more ahead of UT; it would coincide with local mean time along a meridian drifting slowly eastward (reaching Paris and beyond).{{sfn|Irvine|2008}} Thus, the time system would lose its fixed connection to the geographic coordinates based on the [[IERS Reference Meridian|IERS meridian]]. Assuming that there are no major events affecting civilization over the coming centuries, the difference between UTC and UT could reach 0.5 hours after the year 2600 and 6.5 hours around 4600.{{sfn | Allen | 2011a}} | There is a proposal to redefine UTC and abolish leap seconds, so that [[sundial]]s would very slowly get further out of sync with civil time.{{sfn | Allen | 2011b}} The resulting gradual shift of the sun's movements relative to civil time is analogous to the shift of [[season]]s relative to the yearly calendar that results from the calendar year not precisely matching the [[tropical year]] length. This would be a practical change in civil timekeeping, but would take effect slowly over several centuries. UTC (and TAI) would be more and more ahead of UT; it would coincide with local mean time along a meridian drifting slowly eastward (reaching Paris and beyond).{{sfn|Irvine|2008}} Thus, the time system would lose its fixed connection to the geographic coordinates based on the [[IERS Reference Meridian|IERS meridian]]. Assuming that there are no major events affecting civilization over the coming centuries, the difference between UTC and UT could reach 0.5 hours after the year 2600 and 6.5 hours around 4600.{{sfn | Allen | 2011a}} | ||
[[ITU-R|ITU‑R]] Study Group 7 and Working Party 7A were unable to reach consensus on whether to advance the proposal to the 2012 Radiocommunications Assembly; the chairman of Study Group 7 elected to advance the question to the 2012 Radiocommunications Assembly (20 January 2012),{{sfn|Seidelmann|Seago|2011|p=S190}} but consideration of the proposal was postponed by the ITU until the World Radio Conference in 2015.{{sfn |Leap decision postponed|2012}} This conference, in turn, considered the question,<ref>{{Cite | [[ITU-R|ITU‑R]] Study Group 7 and Working Party 7A were unable to reach consensus on whether to advance the proposal to the 2012 Radiocommunications Assembly; the chairman of Study Group 7 elected to advance the question to the 2012 Radiocommunications Assembly (20 January 2012),{{sfn|Seidelmann|Seago|2011|p=S190}} but consideration of the proposal was postponed by the ITU until the World Radio Conference in 2015.{{sfn |Leap decision postponed|2012}} This conference, in turn, considered the question,<ref>{{Cite press release | title = ITU World Radiocommunication Conference set for Geneva, 2–27 November 2015 | publisher = International Telecommunication Union |year = 2015 | access-date = 3 November 2015 | url = https://www.itu.int/net/pressoffice/press_releases/2015/Advisory-08.aspx}}</ref> but no permanent decision was reached; it only chose to engage in further study with the goal of reconsideration in 2023.<ref name=itu.int /> {{update after|2023|12|31}} | ||
Proposals have been made to [[abolish time zones]] and make Coordinated Universal Time the local time worldwide. | Proposals have been made to [[abolish time zones]] and make Coordinated Universal Time the local time worldwide. | ||
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{{Reflist|refs= | {{Reflist|refs= | ||
<ref name=itu.int>{{Cite | <ref name=itu.int>{{Cite press release|url=https://www.itu.int/net/pressoffice/press_releases/2015/53.aspx|title=Coordinated Universal Time (UTC) to retain "leap second"|website=www.itu.int|access-date=12 July 2017}}</ref> | ||
}} | }} | ||
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{{refbegin|2|indent=yes}} | {{refbegin|2|indent=yes}} | ||
* {{Cite book|last1 = Allan |first1=David W. | first2 = Neil| last2 = Ashby | first3 = Clifford C. | last3 = Hodge | publisher = Hewlett-Packard | year = 1997 | title = The Science of Timekeeping }} [[Application note]]. | * {{Cite book|last1 = Allan |first1=David W. | first2 = Neil| last2 = Ashby | first3 = Clifford C. | last3 = Hodge | publisher = Hewlett-Packard | year = 1997 | title = The Science of Timekeeping }} [[Application note]]. | ||
* {{Cite web |last = Allen |first = Steve |url = | * {{Cite web |last = Allen |first = Steve |url = https://www.ucolick.org/~sla/leapsecs/utcdoomed |title = UTC is doomed |access-date = 18 July 2011 |year = 2011a }} | ||
* {{Cite web | last1 = Allen | first1 = Steve | url = | * {{Cite web | last1 = Allen | first1 = Steve | url = https://www.ucolick.org/~sla/leapsecs/ | title = UTC might be redefined without Leap Seconds | access-date = 18 July 2011 | year = 2011b }} | ||
* {{Cite conference | conference = ITU-R Special Rapporteur Group Colloquium on the UTC Time Scale | date = 29 May 2003 | url = | * {{Cite conference | conference = ITU-R Special Rapporteur Group Colloquium on the UTC Time Scale | date = 29 May 2003 | url = https://www.ucolick.org/~sla/leapsecs/torino/arias_3.pdf | title = Rotation of the Earth and Time scales | last1 = Arias | first1 = E. F. | last2 = Guinot | first2 = B. | last3 = Quinn | first3 = T. J. }} | ||
* {{Cite web | ref = {{SfnRef|Aviation Time|2006}} | title = Aviation Time | year = 2006 | access-date = 17 July 2011 | work = AOPA's Path to Aviation | publisher = Aircraft Owners and Pilots Association | url = http://www.aopa.org/path/time.html | archive-url = https://web.archive.org/web/20061127230424/http://www.aopa.org/path/time.html | url-status = dead | archive-date = 27 November 2006 }} | * {{Cite web | ref = {{SfnRef|Aviation Time|2006}} | title = Aviation Time | year = 2006 | access-date = 17 July 2011 | work = AOPA's Path to Aviation | publisher = Aircraft Owners and Pilots Association | url = http://www.aopa.org/path/time.html | archive-url = https://web.archive.org/web/20061127230424/http://www.aopa.org/path/time.html | url-status = dead | archive-date = 27 November 2006 }} | ||
* {{Cite web |ref={{SfnRef| Bulletin C| 2019}} |url= | * {{Cite web |ref={{SfnRef| Bulletin C| 2019}} |url=https://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat |title=Bulletin C |publisher=[[International Earth Rotation and Reference Systems Service]] |date=4 July 2019 }} | ||
*{{citation |editor-last=Blair |editor-first=Byron E. |title=Time and Frequency: Theory and Fundamentals |url=https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nbsmonograph140.pdf |publisher=National Bureau of Standards, National Institute of Standards and Technology since 1988 |year=1974 |page=32 }} | *{{citation |editor-last=Blair |editor-first=Byron E. |title=Time and Frequency: Theory and Fundamentals |url=https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nbsmonograph140.pdf |publisher=National Bureau of Standards, National Institute of Standards and Technology since 1988 |year=1974 |page=32 }} | ||
* {{Cite web | last1 = Chester | first1 = Geoff | title = Wait a second... 2015 will be a little longer | date = 15 June 2015 | website = CHIPS: The Department of the Navy's Information Technology Magazine | publisher = Department of the Navy | url = https://www.doncio.navy.mil/chips/ArticleDetails.aspx?ID=6471 | access-date = 12 March 2021 }} | * {{Cite web | last1 = Chester | first1 = Geoff | title = Wait a second... 2015 will be a little longer | date = 15 June 2015 | website = CHIPS: The Department of the Navy's Information Technology Magazine | publisher = Department of the Navy | url = https://www.doncio.navy.mil/chips/ArticleDetails.aspx?ID=6471 | access-date = 12 March 2021 }} | ||
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* {{Cite journal| last1 = Guinot| first1 = Bernard | date = August 2011 | volume=48 | issue=4 | title = Solar time, legal time, time in use | journal = Metrologia | pages =S181–185| doi = 10.1088/0026-1394/48/4/S08|bibcode = 2011Metro..48S.181G }} | * {{Cite journal| last1 = Guinot| first1 = Bernard | date = August 2011 | volume=48 | issue=4 | title = Solar time, legal time, time in use | journal = Metrologia | pages =S181–185| doi = 10.1088/0026-1394/48/4/S08|bibcode = 2011Metro..48S.181G }} | ||
* {{Cite web |ref={{SfnRef|History of TAI-UTC|c. 2009}} |url=http://maia.usno.navy.mil/ser7/tai-utc.dat |archive-url=https://web.archive.org/web/20191019051734/http://maia.usno.navy.mil/ser7/tai-utc.dat |url-status=dead |archive-date=2019-10-19 |title=History of TAI-UTC |publisher=Time Service Dept., [[United States Naval Observatory|U.S. Naval Observatory]] |access-date=4 January 2009 |year=c. 2009 }} | * {{Cite web |ref={{SfnRef|History of TAI-UTC|c. 2009}} |url=http://maia.usno.navy.mil/ser7/tai-utc.dat |archive-url=https://web.archive.org/web/20191019051734/http://maia.usno.navy.mil/ser7/tai-utc.dat |url-status=dead |archive-date=2019-10-19 |title=History of TAI-UTC |publisher=Time Service Dept., [[United States Naval Observatory|U.S. Naval Observatory]] |access-date=4 January 2009 |year=c. 2009 }} | ||
* {{Cite web | last1 = Horzepa | first1 = Stan | title = Surfin': Time for Ham Radio | publisher = American Radio Relay League | date = 17 September 2010 | url = | * {{Cite web | last1 = Horzepa | first1 = Stan | title = Surfin': Time for Ham Radio | publisher = American Radio Relay League | date = 17 September 2010 | url = https://www.arrl.org/news/surfin-time-for-ham-radio | access-date = 24 October 2011 }} | ||
* {{Cite book|last1=Howse|first1=Derek|title=Greenwich Time and the Longitude|year=1997|publisher=Philip Wilson|location=London|isbn=0-85667-468-0|url-access=registration|url=https://archive.org/details/greenwichtimelon0000hows}} | * {{Cite book|last1=Howse|first1=Derek|title=Greenwich Time and the Longitude|year=1997|publisher=Philip Wilson|location=London|isbn=0-85667-468-0|url-access=registration|url=https://archive.org/details/greenwichtimelon0000hows}} | ||
* {{Cite web | ref = {{sfnRef|How NTP Works|2011}} | url = | * {{Cite web | ref = {{sfnRef|How NTP Works|2011}} | url = https://www.eecis.udel.edu/~mills/ntp/html/warp.html | title = How NTP Works | date = 28 July 2011 | work = NTP: The Network Time Protocol }} See heading "NTP Timescale and Data Formats". | ||
* {{Cite web| ref = {{SfnRef|IAU resolutions|1976}}| year = 1976| url = | * {{Cite web| ref = {{SfnRef|IAU resolutions|1976}}| year = 1976| url = https://www.iau.org/static/resolutions/IAU1976_French.pdf| title = IAU resolutions adopted at the XVIth General Assembly, Grenoble, France, 1976}} Resolution no. 3 by Commissions 4 (Ephemerides/Ephémérides) and 31 (Time/L'Heure) (near the end of the document) "recommend that the following notations be used in all languages", UT0(i), UT1(i), UT2(i), UTC, UTC(i), UT, where (i) is institution "i". | ||
* {{Cite web| ref = {{SfnRef|Iceland|2011}}| title = Iceland| year = 2011| url = http://wwp.greenwichmeantime.com/time-zone/europe/iceland/ | * {{Cite web| ref = {{SfnRef|Iceland|2011}}| title = Iceland| year = 2011| url = http://wwp.greenwichmeantime.com/time-zone/europe/iceland/| archive-url = https://web.archive.org/web/20111018222316/http://wwp.greenwichmeantime.com/time-zone/europe/iceland/| archive-date = 18 October 2011}} | ||
* {{Cite web| author = International Earth Rotation and Reference Systems Service| author-link = International Earth Rotation and Reference Systems Service| title = IERS Bulletins| date = 19 July 2011| url = https://www.iers.org/IERS/EN/Publications/Bulletins/bulletins.html}} | |||
* {{Cite web| author = International Earth Rotation and Reference Systems Service| author-link = International Earth Rotation and Reference Systems Service| title = IERS Bulletins| date = 19 July 2011| url = | |||
* {{Cite news | last1 = Irvine | first1 = Chris | title = Scientists propose 'leap hour' to fix time system | date = 18 December 2008 | newspaper = The Telegraph | url = https://www.telegraph.co.uk/science/science-news/3817096/Scientists-propose-leap-hour-to-fix-time-system.html | archive-url = https://web.archive.org/web/20110514005932/http://www.telegraph.co.uk/science/science-news/3817096/Scientists-propose-leap-hour-to-fix-time-system.html | url-status = dead | archive-date = 14 May 2011 }} | * {{Cite news | last1 = Irvine | first1 = Chris | title = Scientists propose 'leap hour' to fix time system | date = 18 December 2008 | newspaper = The Telegraph | url = https://www.telegraph.co.uk/science/science-news/3817096/Scientists-propose-leap-hour-to-fix-time-system.html | archive-url = https://web.archive.org/web/20110514005932/http://www.telegraph.co.uk/science/science-news/3817096/Scientists-propose-leap-hour-to-fix-time-system.html | url-status = dead | archive-date = 14 May 2011 }} | ||
* {{Cite web |author= ITU Radiocommunication Assembly |url= | * {{Cite web |author= ITU Radiocommunication Assembly |url= https://www.itu.int/dms_pubrec/itu-r/rec/tf/R-REC-TF.460-6-200202-I!!PDF-E.pdf |title= Standard-frequency and time-signal emissions |year= 2002 |publisher= International Telecommunication Union |access-date= 2 August 2011 }} | ||
* {{Cite web|url= | * {{Cite web|url=https://www.apparent-wind.com/gmt-explained.html|title=A Few Facts Concerning GMT, UT, and the RGO|access-date=17 July 2011|last1=Langley|first1=Richard B.|date=20 January 1999}} | ||
* {{Cite news| ref = {{sfnref|Leap decision postponed|2012}}| url = https://www.bbc.co.uk/news/science-environment-16625614| work = BBC News| title = Leap second decision is postponed| date = 19 January 2012}} | * {{Cite news| ref = {{sfnref|Leap decision postponed|2012}}| url = https://www.bbc.co.uk/news/science-environment-16625614| work = BBC News| title = Leap second decision is postponed| date = 19 January 2012}} | ||
* {{Cite journal |last1=Markowitz |first1=W. |date=August 1958 |title=Frequency of caesium in terms of Ephemeris Time |journal=Physical Review Letters |volume=1 |issue=3 |pages=105–7 |url=http://www.leapsecond.com/history/1958-PhysRev-v1-n3-Markowitz-Hall-Essen-Parry.pdf |access-date=18 October 2008 |doi=10.1103/PhysRevLett.1.105 |last2=Hall |first2=R. |last3=Essen |first3=L. |last4=Parry |first4=J. |bibcode=1958PhRvL...1..105M }} | * {{Cite journal |last1=Markowitz |first1=W. |date=August 1958 |title=Frequency of caesium in terms of Ephemeris Time |journal=Physical Review Letters |volume=1 |issue=3 |pages=105–7 |url=http://www.leapsecond.com/history/1958-PhysRev-v1-n3-Markowitz-Hall-Essen-Parry.pdf |access-date=18 October 2008 |doi=10.1103/PhysRevLett.1.105 |last2=Hall |first2=R. |last3=Essen |first3=L. |last4=Parry |first4=J. |bibcode=1958PhRvL...1..105M }} | ||
*{{Cite journal| issue = 1| pages = 345–366| last = Fleming| first = Sandford| title = Time-reckoning for the twentieth century| journal = Annual Report of the Board of Regents of the Smithsonian Institution| date = 1886| url = https://library.si.edu/digital-library/book/annualreportofbo18861smit}} Reprinted in 1889: {{Internet Archive|timereckoningfor00flem|''Time-reckoning for the twentieth century''}} | *{{Cite journal| issue = 1| pages = 345–366| last = Fleming| first = Sandford| title = Time-reckoning for the twentieth century| journal = Annual Report of the Board of Regents of the Smithsonian Institution| date = 1886| url = https://library.si.edu/digital-library/book/annualreportofbo18861smit}} Reprinted in 1889: {{Internet Archive|timereckoningfor00flem|''Time-reckoning for the twentieth century''}} | ||
* {{Cite book| year = 1988 | last=Markowitz | first = Wm. | editor1-last = Babcock | editor1-first = A. K. | editor2-last = Wilkins | editor2-first = G. A. | title = The Earth's Rotation and Reference Frames for Geodesy and Geophysics: Proceedings of the 128th Symposium of the International Astronomical Union, held in Coolfont, West Virginia, U.S.A., 20–24 October 1986 | | * {{Cite book| year = 1988 | last=Markowitz | first = Wm. | editor1-last = Babcock | editor1-first = A. K. | editor2-last = Wilkins | editor2-first = G. A. | title = The Earth's Rotation and Reference Frames for Geodesy and Geophysics: Proceedings of the 128th Symposium of the International Astronomical Union, held in Coolfont, West Virginia, U.S.A., 20–24 October 1986 | series = International Astronomical Union Symposia | volume = 128 | chapter = Comparisons of ET (Solar), ET (Lunar), UT and TDT | publisher = Kluwer Academic Publishers | location = Dordrecht | bibcode=1988IAUS..128..413M | isbn = 978-90-277-2657-5 | pages = 413–418}} | ||
* {{Cite journal |author=McCarthy, Dennis D. |title=Astronomical Time |journal=Proc. IEEE |volume=79 |issue=7 |pages=915–920 |date=July 1991 |doi=10.1109/5.84967 |url= | * {{Cite journal |author=McCarthy, Dennis D. |title=Astronomical Time |journal=Proc. IEEE |volume=79 |issue=7 |pages=915–920 |date=July 1991 |doi=10.1109/5.84967 |url=https://www.cl.cam.ac.uk/~mgk25/volatile/astronomical-time.pdf |author-link=Dennis McCarthy (scientist) }} | ||
* {{Cite book | last1 = McCarthy | first1 = Dennis D. | author1-link = Dennis McCarthy (scientist) | last2 = Seidelmann | first2 = P. Kenneth | year = 2009 | publisher = Wiley VCH | location = Weinheim | title = TIME From Earth Rotation to Atomic Physics | isbn = 978-3-527-40780-4}} | * {{Cite book | last1 = McCarthy | first1 = Dennis D. | author1-link = Dennis McCarthy (scientist) | last2 = Seidelmann | first2 = P. Kenneth | year = 2009 | publisher = Wiley VCH | location = Weinheim | title = TIME From Earth Rotation to Atomic Physics | isbn = 978-3-527-40780-4}} | ||
*{{Cite web | title = Note on Coordinated Universal Time (CCTF/09-32) | url = | *{{Cite web | title = Note on Coordinated Universal Time (CCTF/09-32) | url = https://www1.bipm.org/cc/CCTF/Allowed/18/CCTF_09-32_noteUTC.pdf | access-date = 3 September 2017 | page = 4 | date = 2 June 2009 | first = D. | last = McCarthy | author-link = Dennis McCarthy (scientist) }} | ||
*{{Cite book | last1 = McCarthy | first1 = D. | author-link1 = Dennis McCarthy (scientist) | last2 = Guinot | first2 = B. | chapter = Time | title = Explanatory Supplement to the Astronomical Almanac | edition = 3rd | editor-last1 = Urban | editor-first1= Sean E. | editor-last2 = Seidelmann | editor-first2 = P. Kenneth | publisher = University Science Books | location = Mill Valley, CA | date = 2013}} | *{{Cite book | last1 = McCarthy | first1 = D. | author-link1 = Dennis McCarthy (scientist) | last2 = Guinot | first2 = B. | chapter = Time | title = Explanatory Supplement to the Astronomical Almanac | edition = 3rd | editor-last1 = Urban | editor-first1= Sean E. | editor-last2 = Seidelmann | editor-first2 = P. Kenneth | publisher = University Science Books | location = Mill Valley, CA | date = 2013}} | ||
* {{Cite web | ref = {{SfnRef|Military & Civilian Time Designations|n.d.}} | url = http://wwp.greenwichmeantime.com/info/timezone.htm | publisher = wwp | title = Military & Civilian Time Designations | access-date = 2 June 2007 | archive-url = https://web.archive.org/web/20160914030025/http://wwp.greenwichmeantime.com/info/timezone.htm | archive-date = 14 September 2016 | url-status = dead }} | * {{Cite web | ref = {{SfnRef|Military & Civilian Time Designations|n.d.}} | url = http://wwp.greenwichmeantime.com/info/timezone.htm | publisher = wwp | title = Military & Civilian Time Designations | access-date = 2 June 2007 | archive-url = https://web.archive.org/web/20160914030025/http://wwp.greenwichmeantime.com/info/timezone.htm | archive-date = 14 September 2016 | url-status = dead }} | ||
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* {{Cite web |last1=Nelson |first1=G.K. |last2=Lombardi |first2=M.A. |last3=Okayama |first3=D.T. |title=NIST Time and Frequency Radio Stations: WWV, WWVH, and WWVB |year=2005 |publisher=[[National Institute of Standards and Technology]] |url=https://www.nist.gov/calibrations/upload/sp250-67.pdf |id=(Special Publication 250-67) |url-status=live |archive-url=https://web.archive.org/web/20080626003023/http://ts.nist.gov/MeasurementServices/Calibrations/upload/SP250-67.pdf |archive-date=26 June 2008 }} | * {{Cite web |last1=Nelson |first1=G.K. |last2=Lombardi |first2=M.A. |last3=Okayama |first3=D.T. |title=NIST Time and Frequency Radio Stations: WWV, WWVH, and WWVB |year=2005 |publisher=[[National Institute of Standards and Technology]] |url=https://www.nist.gov/calibrations/upload/sp250-67.pdf |id=(Special Publication 250-67) |url-status=live |archive-url=https://web.archive.org/web/20080626003023/http://ts.nist.gov/MeasurementServices/Calibrations/upload/SP250-67.pdf |archive-date=26 June 2008 }} | ||
* {{Cite conference |last1=Nelson |first1=Robert A. |last2=McCarthy |first2=Dennis D. |author2-link=Dennis McCarthy (scientist) |url=http://www.navcen.uscg.gov/pdf/cgsicMeetings/45/29a%20UTCLeapSecond.ppt |title=Coordinated Universal Time (UTC) and the Future of the Leap Second |conference=Civil GPS Interface Committee |publisher=[[United States Coast Guard]] |date=13 September 2005 |url-status=dead |archive-url=https://web.archive.org/web/20110429231210/http://www.navcen.uscg.gov/pdf/cgsicMeetings/45/29a%20UTCLeapSecond.ppt |archive-date=29 April 2011 }} | * {{Cite conference |last1=Nelson |first1=Robert A. |last2=McCarthy |first2=Dennis D. |author2-link=Dennis McCarthy (scientist) |url=http://www.navcen.uscg.gov/pdf/cgsicMeetings/45/29a%20UTCLeapSecond.ppt |title=Coordinated Universal Time (UTC) and the Future of the Leap Second |conference=Civil GPS Interface Committee |publisher=[[United States Coast Guard]] |date=13 September 2005 |url-status=dead |archive-url=https://web.archive.org/web/20110429231210/http://www.navcen.uscg.gov/pdf/cgsicMeetings/45/29a%20UTCLeapSecond.ppt |archive-date=29 April 2011 }} | ||
* {{Cite journal|last1=Nelson|first1=Robert A.|last2=McCarthy|first2=Dennis D.|last3=Malys|first3=S.|last4=Levine|first4=J.|last5=Guinot|first5=B.|last6=Fliegel|first6=H. F.|last7=Beard|first7=R. L.|last8=Bartholomew|first8=T. R.|title=The leap second: its history and possible future|journal=Metrologia|volume=38|issue=6|pages=509–529|year=2001|doi=10.1088/0026-1394/38/6/6|url= | * {{Cite journal|last1=Nelson|first1=Robert A.|last2=McCarthy|first2=Dennis D.|last3=Malys|first3=S.|last4=Levine|first4=J.|last5=Guinot|first5=B.|last6=Fliegel|first6=H. F.|last7=Beard|first7=R. L.|last8=Bartholomew|first8=T. R.|title=The leap second: its history and possible future|journal=Metrologia|volume=38|issue=6|pages=509–529|year=2001|doi=10.1088/0026-1394/38/6/6|url=https://www.cl.cam.ac.uk/~mgk25/time/metrologia-leapsecond.pdf|bibcode=2001Metro..38..509N}} | ||
* {{Cite journal | last1 = Seidelmann | first1 = P. Kenneth | last2 = Seago | first2 = John H. | date = August 2011 | volume = 48 | issue = 4 | title = Time scales, their users, and leap seconds | journal = Metrologia | pages = S186–S194 | url = http://www.agi.com/resources/user-resources/downloads/white-paper.aspx?id=158 | doi = 10.1088/0026-1394/48/4/S09 | bibcode = 2011Metro..48S.186S | url-status = dead | archive-url = https://web.archive.org/web/20121019144359/http://www.agi.com/resources/user-resources/downloads/white-paper.aspx?id=158 | archive-date = 19 October 2012 | df = dmy-all }} | * {{Cite journal | last1 = Seidelmann | first1 = P. Kenneth | last2 = Seago | first2 = John H. | date = August 2011 | volume = 48 | issue = 4 | title = Time scales, their users, and leap seconds | journal = Metrologia | pages = S186–S194 | url = http://www.agi.com/resources/user-resources/downloads/white-paper.aspx?id=158 | doi = 10.1088/0026-1394/48/4/S09 | bibcode = 2011Metro..48S.186S | url-status = dead | archive-url = https://web.archive.org/web/20121019144359/http://www.agi.com/resources/user-resources/downloads/white-paper.aspx?id=158 | archive-date = 19 October 2012 | df = dmy-all }} | ||
* {{Cite web | last1 = Seaman | first1 = Rob | url = http://iraf.noao.edu/~seaman/leap/ | title = A Proposal to Upgrade UTC | access-date = 18 July 2011 | year = 2003 | url-status = dead | archive-url = https://web.archive.org/web/20110723140249/http://iraf.noao.edu/~seaman/leap/ | archive-date = 23 July 2011 | df = dmy-all }} | * {{Cite web | last1 = Seaman | first1 = Rob | url = http://iraf.noao.edu/~seaman/leap/ | title = A Proposal to Upgrade UTC | access-date = 18 July 2011 | year = 2003 | url-status = dead | archive-url = https://web.archive.org/web/20110723140249/http://iraf.noao.edu/~seaman/leap/ | archive-date = 23 July 2011 | df = dmy-all }} | ||
* {{Cite book |url=https://archive.org/stream/131123ExplanatorySupplementAstronomicalAlmanac/131123-explanatory-supplement-astronomical-almanac#page/n56/mode/1up |editor-last=Seidelmann |editor-first=P Kenneth |title=Explanatory Supplement to the Astronomical Almanac |publisher=University Science Books |edition=2nd |location=Mill Valley, CA |year=1992 |isbn=0-935702-68-7 }} | * {{Cite book |url=https://archive.org/stream/131123ExplanatorySupplementAstronomicalAlmanac/131123-explanatory-supplement-astronomical-almanac#page/n56/mode/1up |editor-last=Seidelmann |editor-first=P Kenneth |title=Explanatory Supplement to the Astronomical Almanac |publisher=University Science Books |edition=2nd |location=Mill Valley, CA |year=1992 |isbn=0-935702-68-7 }} | ||
* {{Cite journal | last1 = Stephenson | first1 = F. R. | last2 = Morrison | first2 = L. V. |title=Long-term fluctuations in the Earth's rotation: 700 BC to AD 1990 | journal = Philosophical Transactions of the Royal Society A | year = 1995 | pages = 165–202 | bibcode = 1995RSPTA.351..165S | volume = 351 | doi = 10.1098/rsta.1995.0028 | issue = 1695| s2cid = 120718607 }} | * {{Cite journal | last1 = Stephenson | first1 = F. R. | last2 = Morrison | first2 = L. V. |title=Long-term fluctuations in the Earth's rotation: 700 BC to AD 1990 | journal = Philosophical Transactions of the Royal Society A | year = 1995 | pages = 165–202 | bibcode = 1995RSPTA.351..165S | volume = 351 | doi = 10.1098/rsta.1995.0028 | issue = 1695| s2cid = 120718607 }} | ||
* {{Cite web | ref = {{sfnref| | * {{Cite web | ref = {{sfnref|15 U.S. Code § 261|2007}} | title = 15 U.S. Code § 261 - Zones for standard time; interstate or foreign commerce | year = 2007 | url = https://www.law.cornell.edu/uscode/text/15/261 | work = [[United States Code|U.S. Code]] | publisher = Legal Information Institute }} | ||
* {{Cite web | url = | * {{Cite web | ref = {{sfnref|15 U.S. Code § 260a|2005}} | title = 15 U.S. Code § 260a - Advancement of time or changeover dates | year = 2005 | url = https://www.law.cornell.edu/uscode/text/15/260a | work = [[United States Code|U.S. Code]] | publisher = Legal Information Institute }} | ||
* {{Cite web | url = https://www.cl.cam.ac.uk/~mgk25/volatile/ITU-R-TF.460-4.pdf | title = TF.460-4: Standard-frequency and time-signal emissions | publisher = International Telecommunication Union | at = Annex I | year = 1986 }} | |||
* {{Cite web| ref = {{SfnRef|United States Naval Observatory|n.d.}}| access-date = 10 October 2013| title = Universal Time| author = United States Naval Observatory| url = http://aa.usno.navy.mil/faq/docs/UT.php| archive-date = 22 July 2011| archive-url = https://web.archive.org/web/20110722212121/http://aa.usno.navy.mil/faq/docs/UT.php| url-status = dead}} | * {{Cite web| ref = {{SfnRef|United States Naval Observatory|n.d.}}| access-date = 10 October 2013| title = Universal Time| author = United States Naval Observatory| url = http://aa.usno.navy.mil/faq/docs/UT.php| archive-date = 22 July 2011| archive-url = https://web.archive.org/web/20110722212121/http://aa.usno.navy.mil/faq/docs/UT.php| url-status = dead}} | ||
* {{Cite web | title = Universal Time | work = Oxford Dictionaries: British and World English | access-date = 6 August 2014 | url = http://www.oxforddictionaries.com/us/definition/american_english/Universal-Time | publisher = Oxford University Press | ref = {{SfnRef|Universal Time|n.d.}} }} | * {{Cite web | title = Universal Time | work = Oxford Dictionaries: British and World English | access-date = 6 August 2014 | url = http://www.oxforddictionaries.com/us/definition/american_english/Universal-Time | publisher = Oxford University Press | ref = {{SfnRef|Universal Time|n.d.}} }} | ||
* {{Cite news |first=Jack |last=Williams |title=Understanding and using Zulu time |url=https://www.usatoday.com/weather/zulu.htm |work=[[USA Today]] |date=17 May 2005 |access-date=25 February 2007 }} | * {{Cite news |first=Jack |last=Williams |title=Understanding and using Zulu time |url=https://www.usatoday.com/weather/zulu.htm |work=[[USA Today]] |date=17 May 2005 |access-date=25 February 2007 |archive-url=https://web.archive.org/web/20070621201746/https://www.usatoday.com/weather/zulu.htm |archive-date=21 June 2007}} | ||
{{refend}} | {{refend}} | ||
| Line 175: | Line 174: | ||
{{Wiktionary|UTC}} | {{Wiktionary|UTC}} | ||
* [https://www.worldtimeserver.com/time-zones/utc/ ''Current'' UTC time] | * [https://www.worldtimeserver.com/time-zones/utc/ ''Current'' UTC time] | ||
* [ | * [https://www.cl.cam.ac.uk/~mgk25/time/zeitgesetz.en.html Definition of Coordinated Universal Time in German law–ZeitG §1 (3)] | ||
* [ | * [https://hpiers.obspm.fr/eop-pc/earthor/utc/TAI-UTC_tab.html International Earth Rotation Service; list of differences between TAI and UTC from 1961 to present] | ||
* [ | * [https://www.w3.org/TR/NOTE-datetime W3C Specification about UTC Date and Time] and {{IETF RFC|3339}}, based on [[ISO 8601]] | ||
* | * {{webarchive|url=https://web.archive.org/web/20110912145747/https://www.ipses.com/prod/timing/UTC-GPS.php?language=en|date=12 September 2011|title=Standard of time definition: UTC, GPS, LORAN and TAI}} | ||
* | * {{webarchive|url=https://web.archive.org/web/20131106032206/https://itunews.itu.int/En/4271-What-is-in-a-nameBROn-the-term-Coordinated-Universal-Time.note.aspx|date=6 November 2013|title=What is in a name? On the term Coordinated Universal Time}} | ||
{{Time topics}} | {{Time topics}} | ||