Leap second: Difference between revisions

Revision as of 10:11, 1 September 2024

Revision as of 08:05, 8 September 2024

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Because the Earth's rotational speed varies in response to climatic and geological events,<ref>{{cite web |url=https://www.iers.org/IERS/EN/Science/EarthRotation/EarthRotation.html |title=IERS science background |publisher=[[IERS]] |___location=Frankfurt am Main |date=2013 |access-date=6 August 2016 |url-status=live |archive-url=https://web.archive.org/web/20160829050135/https://www.iers.org/IERS/EN/Science/EarthRotation/EarthRotation.html |archive-date=29 August 2016}}</ref> UTC leap seconds are irregularly spaced and unpredictable. Insertion of each UTC leap second is usually decided about six months in advance by the [[International Earth Rotation and Reference Systems Service]] (IERS), to ensure that the difference between the UTC and UT1 readings will never exceed 0.9 seconds.<ref name="Bulletin C 49">{{cite web|url=http://hpiers.obspm.fr/eoppc/bul/bulc/bulletinc.49|title=Bulletin C 49|last=Gambis|first=Danie|date=5 January 2015|publisher=[[IERS]]|___location=Paris|access-date=5 January 2015|url-status=live|archive-url=https://web.archive.org/web/20150530123243/https://hpiers.obspm.fr/eoppc/bul/bulc/bulletinc.49|archive-date=30 May 2015}}</ref><ref>{{cite web|url=https://www.theverge.com/2015/1/7/7508651/leap-second-2015-earths-rotation-slowing|title=2015 is getting an extra second and that's a bit of a problem for the internet|author1=James Vincent|website=[[The Verge]]|date=7 January 2015|url-status=live|archive-url=https://web.archive.org/web/20170317175523/http://www.theverge.com/2015/1/7/7508651/leap-second-2015-earths-rotation-slowing|archive-date=17 March 2017}}</ref>

This practice has proven disruptive, particularly in the twenty-first century and especially in services that depend on precise [[timestamp]]ing or time-critical [[process control]]. And since not all computers are adjusted by leap-second, they will display times differing from those that have been adjusted.<ref>{{cite journal |last1=Finkleman |first1=David |last2=Allen |first2=Steve |last3=Seago |first3=John |last4=Seaman |first4=Rob |last5=Seidelmann |first5=P. Kenneth |year=2011 |title=The Future of Time: UTC and the Leap Second |url=https://www.americanscientist.org/article/the-future-of-time-utc-and-the-leap-second |journal=[[American Scientist]] |volume=99 |issue=4 |pages=312–319 |arxiv=1106.3141 |doi=10.1511/2011.91.312 |s2cid=118403321 |doi-access=free}}</ref> After many years of discussions by different standards bodies, in November 2022, at the 27th [[General Conference on Weights and Measures]], it was decided to abandon the leap second by or before 2035.<ref name=AFP/><ref name=gibney/>

==History==

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Proposed alternatives to the leap second are the leap hour, which requires changes only once every few centuries;<ref>{{cite magazine |title=Scientists propose 'leap hour' to fix time system |url=https://www.newindianexpress.com/magazine/2008/dec/18/scientists-propose-leap-hour-to-fix-time-system-11669.html |magazine=New Scientist |via=The New Indian Express |access-date=3 September 2022 |orig-date=2008-12-18 |date=14 May 2012}}</ref> and the leap minute, with changes coming every half-century.<ref name="Martin-2024" /><ref>{{Cite news| issn = 0362-4331| last = Richtel| first = Matt| title = A Giant Leap for the Leap Second. Is Humankind Ready?| work = The New York Times| access-date = 23 January 2024| date = 3 November 2023| url = https://www.nytimes.com/2023/11/03/science/time-leap-second.html}}</ref>

On 18 November 2022, the [[General Conference on Weights and Measures]] (CGPM) resolved to eliminate leap seconds by or before 2035. The difference between atomic and astronomical time will be allowed to grow to a larger value yet to be determined. A suggested possible future measure would be to let the discrepancy increase to a full minute, which would take 50 to 100&nbsp;years, and then have the last minute of the day taking two minutes in a "kind of smear" with no discontinuity. The year 2035 for eliminating leap seconds was chosen considering Russia's request to extend the timeline to 2040, since, unlike the United States's [[global navigation satellite system]], [[GPS]], which does not adjust its time with leap seconds, Russia's system, [[GLONASS]], does adjust its time with leap seconds.<ref name="AFP">{{cite news |first= |date=18 November 2022 |title=Do not adjust your clock: scientists call time on the leap second |url=https://www.theguardian.com/world/2022/nov/18/do-not-adjust-your-clock-scientists-call-time-on-the-leap-second |website=[[The Guardian]] |department=World News |agency=[[Agence France-Presse]]}}</ref><ref name="gibney">{{cite journal |last=Gibney |first=Elizabeth |author-link=Elizabeth Gibney |date=18 November 2022 |title=The leap second's time is up: world votes to stop pausing clocks |journal=[[Nature (journal)|Nature]] |volume=612 |issue=7938 |page=18 |bibcode=2022Natur.612...18G |doi=10.1038/d41586-022-03783-5 |issn=0028-0836 |pmid=36400956 |doi-access=free}}</ref>

ITU World Radiocommunication Conference 2023 (WRC-23), which was held in Dubai (United Arab Emirates) from 20 November to 15 December 2023 formally recognized the [https://www.bipm.org/en/cgpm-2022/resolution-4 Resolution 4] of the 27th CGPM (2022) which decides that the maximum value for the difference (UT1-UTC) will be increased in, or before, 2035.<ref>{{cite web |url=https://www.bipm.org/en/-/2023-12-12-wrc-dubai |title=ITU-R and BIPM work together at the World Radiocommunication Conference |website=BIPM}}</ref>