Leap second: Difference between revisions

Revision as of 20:30, 30 March 2025

Revision as of 23:14, 17 April 2025

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The scheduling of leap seconds was initially delegated to the [[Bureau International de l'Heure]] (BIH), but passed to the International Earth Rotation and Reference Systems Service (IERS) on 1 January 1988. IERS usually decides to apply a leap second whenever the difference between UTC and UT1 approaches 0.6 s, in order to keep the difference between UTC and UT1 from exceeding 0.9 s.

The UTC standard allows leap seconds to be applied at the end of any UTC month, with first preference to June and December and second preference to March and September. {{As of|May 2023}}, all of them have been inserted at the end of either 30 June or 31 December. IERS publishes announcements every six months, whether leap seconds are to occur or not, in [http://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat its "Bulletin C"]. Such announcements are typically published well in advance of each possible leap second date – usually in early January for 30 June and in early July for 31 December.<ref name="Bulletin C 36">{{cite web|last=Gambis|first=Daniel|title=Bulletin C 36|publisher=[[International Earth Rotation and Reference Systems Service|IERS EOP PC]], [[Observatoire de Paris]]|___location=Paris|date=4 July 2008|url=http://tycho.usno.navy.mil/bulletinc2008.html|access-date=18 April 2010|url-status=livedead|archive-url=https://web.archive.org/web/20091006221408/http://tycho.usno.navy.mil/bulletinc2008.html|archive-date=6 October 2009}}</ref><ref>{{Cite web|url=http://www.livescience.com/strangenews/081208-leap-second.html|title=2008 Will Be Just a Second Longer|author=Andrea Thompson|access-date=29 December 2008|publisher=Live Science|date=8 December 2008|url-status=live|archive-url=https://web.archive.org/web/20081212222023/http://www.livescience.com/strangenews/081208-leap-second.html|archive-date=12 December 2008}}</ref> Some [[time signal]] broadcasts give voice announcements of an impending leap second.

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A number of objections to the proposal have been raised. P. Kenneth Seidelmann, editor of the Explanatory Supplement to the Astronomical Almanac, wrote a letter lamenting the lack of consistent public information about the proposal and adequate justification.<ref>{{cite mailing list |url=https://lists.igs.org/pipermail/igsmail/2005/006563.html |title=UTC redefinition or change |author=P. Kenneth Seidelmann |mailing-list=IGS Mail}}</ref> In an [[op-ed]] for ''[[Science News]]'', Steve Allen of the [[University of California, Santa Cruz]] said that the process has a large impact on astronomers.<ref>{{cite magazine |last=Cowen |first=Ron |date=22 April 2006 |title=To Leap or Not to Leap: Scientists debate a timely issue |url=https://www.sciencenews.org/article/leap-or-not-leap |url-status=live |magazine=[[Science News]] |archive-url=https://web.archive.org/web/20230526024544/https://www.sciencenews.org/article/leap-or-not-leap |archive-date=26 May 2023 |access-date=26 May 2023}}</ref>

At the 2014 General Assembly of the [[International Union of Radio Scientists]] (URSI), Demetrios Matsakis, the [[United States Naval Observatory]]'s Chief Scientist for Time Services, presented the reasoning in favor of the redefinition and rebuttals to the arguments made against it.<ref>{{cite web |url=http://tycho.usno.navy.mil/papers/ts-2014/Matsakis-LeapSecondComments.URSI-2014.pdf |title=Comments on the Debate over the Proposal to Redefine UTC |author1=Demetrios Matsakis |date=18 August 2014 |access-date=31 October 2017 |url-status=livedead |archive-url=https://web.archive.org/web/20170208050335/http://tycho.usno.navy.mil/papers/ts-2014/Matsakis-LeapSecondComments.URSI-2014.pdf |archive-date=8 February 2017}}</ref> He stressed the practical inability of software programmers to allow for the fact that leap seconds make time appear to go backwards, particularly when most of them do not even know that leap seconds exist. The possibility of leap seconds being a hazard to navigation was presented, as well as the observed effects on commerce.

The United States formulated its position on this matter based upon the advice of the [[National Telecommunications and Information Administration]]<ref>{{cite web|url=https://www.ntia.doc.gov/files/ntia/publications/ai_1.14_usa_proposal_2014-02-06_0.pdf|title=United States Proposals, Proposal for the Work of the Conference, Agenda Item 1.14|publisher=[[National Telecommunications and Information Administration]]}}</ref> and the [[Federal Communications Commission]] (FCC), which solicited comments from the general public.<ref>{{cite web|url=https://apps.fcc.gov/edocs_public/attachmatch/DA-14-88A1.pdf|title=FCC Seeks Comment On Recommendations Approved By The Advisory Committee For The 2015 World Radiocommunication Conference|publisher=[[Federal Communications Commission]]|date=28 January 2014|url-status=live|archive-url=https://web.archive.org/web/20140729075437/https://apps.fcc.gov/edocs_public/attachmatch/DA-14-88A1.pdf|archive-date=29 July 2014}}</ref> This position is in favor of the redefinition.<ref>{{cite web|url=https://www.ntia.doc.gov/files/ntia/publications/sitt-stit-357221-v1-citel_presentation_for_regional_meetings_on_wrc-15-r2.ppt|title=Preliminary Views and Proposals Regarding WRC-15 Agenda Items|publisher=[[Organization of American States]]|format=PPT|url-status=live|archive-url=https://web.archive.org/web/20140729090447/http://www.ntia.doc.gov/files/ntia/publications/sitt-stit-357221-v1-citel_presentation_for_regional_meetings_on_wrc-15-r2.ppt|archive-date=29 July 2014}}</ref>{{efn|The FCC has posted its received comments, which can be found using their search engine for proceeding 04–286 and limiting the "received period" to those between 27 January and 18 February 2014, inclusive.<ref>{{cite web|url=http://apps.fcc.gov/ecfs/comment_search/execute?proceeding=04-286&applicant=&lawfirm=&author=&disseminated.minDate=&disseminated.maxDate=&received.minDate=1%2F27%2F14&received.maxDate=2%2F18%2F14&dateCommentPeriod.minDate=&dateCommentPeriod.maxDate=&dateReplyComment.minDate=&dateReplyComment.maxDate=&address.city=&address.state.stateCd=&address.zip=&daNumber=&fileNumber=&bureauIdentificationNumber=&reportNumber=&submissionTypeId=&__checkbox_exParte=true|title=Search for Filings Results|work=fcc.gov|url-status=live|archive-url=https://web.archive.org/web/20150701090036/http://apps.fcc.gov/ecfs/comment_search/execute?proceeding=04-286&applicant=&lawfirm=&author=&disseminated.minDate=&disseminated.maxDate=&received.minDate=1%2F27%2F14&received.maxDate=2%2F18%2F14&dateCommentPeriod.minDate=&dateCommentPeriod.maxDate=&dateReplyComment.minDate=&dateReplyComment.maxDate=&address.city=&address.state.stateCd=&address.zip=&daNumber=&fileNumber=&bureauIdentificationNumber=&reportNumber=&submissionTypeId=&__checkbox_exParte=true|archive-date=1 July 2015}}</ref>}}