Editing Leap second (section)

==Future==
{{More citations needed|section|date=December 2023}}
The TAI and UT1 time scales are precisely defined, the former by atomic clocks (and thus independent of Earth's rotation) and the latter by astronomical observations (that measure actual planetary rotation and thus the solar time at the [[IERS Reference Meridian]] at Greenwich). UTC (on which [[civil time]] is usually based) is a compromise, stepping with atomic seconds but periodically reset by a leap second to match UT1.

The irregularity and unpredictability of UTC leap seconds is problematic for several areas, especially [[computing]] (see [[#Issues created by insertion (or removal) of leap seconds|below]]). With increasing requirements for [[timestamp]] accuracy in systems such as process automation and [[high-frequency trading]],<ref>{{Cite news| title = Time Split to the Nanosecond Is Precisely What Wall Street Wants |newspaper =[[The New York Times]]| access-date = 13 December 2022| url = https://www.nytimes.com/2018/06/29/technology/computer-networks-speed-nasdaq.html |date = 29 June 2018}}</ref> this raises a number of issues. Consequently, the long-standing practice of inserting leap seconds is under review by the relevant international standards body.<ref>{{Cite web |last=Dwyer |first=Colin |date=29 December 2016 |title=With A Leap Second, 2016 Promises To Linger Just A Little Bit Longer |url=https://www.npr.org/sections/thetwo-way/2016/12/29/507422729/with-a-leap-second-2016-promises-to-linger-just-a-little-bit-longer |url-status=live |archive-url=https://web.archive.org/web/20230102214327/https://www.npr.org/sections/thetwo-way/2016/12/29/507422729/with-a-leap-second-2016-promises-to-linger-just-a-little-bit-longer |archive-date=2 January 2023 |access-date=24 February 2023 |website=[[NPR]]}}</ref>

===Elimination proposals===
{{anchor|Proposal to abolish leap seconds}}
On 5 July 2005, the Head of the Earth Orientation Center of the IERS sent a notice to IERS Bulletins C and D subscribers, soliciting comments on a U.S. proposal before the ITU-R Study Group 7's WP7-A to eliminate leap seconds from the UTC broadcast standard before 2008 (the [[ITU-R]] is responsible for the definition of UTC).{{efn|''[[The Wall Street Journal]]'' noted that the proposal was considered by a U.S. official at the time to be a "private matter internal to the ITU."<ref>{{cite news |url=https://www.wsj.com/articles/SB112258962467199210?mod=home_page_one_us |title=Why the U.S. Wants To End the Link Between Time and Sun |newspaper=The Wall Street Journal |access-date=31 October 2017 |url-status=live |archive-url=https://web.archive.org/web/20171107010404/https://www.wsj.com/articles/SB112258962467199210?mod=home_page_one_us |archive-date=7 November 2017}}</ref>}} It was expected to be considered in November 2005, but the discussion has since been postponed.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/4420084.stm |title=Leap second talks are postponed |work=[[BBC News]] |access-date=31 October 2017 |url-status=live |archive-url=https://web.archive.org/web/20171107031708/http://news.bbc.co.uk/2/hi/science/nature/4420084.stm |archive-date=7 November 2017}}</ref> Under the proposal, leap seconds would be technically replaced by leap hours as an attempt to satisfy the legal requirements of several ITU-R member nations that civil time be astronomically tied to the Sun.

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=dead |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>}}

In 2011, Chunhao Han of the [[Beijing Global Information Center of Application and Exploration]] said China had not decided what its vote would be in January 2012, but some Chinese scholars consider it important to maintain a link between civil and astronomical time due to Chinese tradition. The 2012 vote was ultimately deferred.<ref name=merali2011>{{cite journal|last=Merali|first=Zeeya|date=8 November 2011|title=Time is running out for the leap second|journal=Nature|volume=479 |issue=7372 |page=158 |doi=10.1038/479158a |pmid=22071738 |bibcode=2011Natur.479..158M |s2cid=8220495 |doi-access=free }}</ref> At an ITU/BIPM-sponsored workshop on the leap second, Han expressed his personal view in favor of abolishing the leap second,<ref>{{cite web|url=https://www.itu.int/dms_pub/itu-r/oth/0a/0e/R0A0E0000960001PDFE.pdf|title=Conception, Definition and Realization of Time Scale in GNSS|last=Han|first=Chunhao|date=19 September 2013|url-status=live|archive-url=https://web.archive.org/web/20140905221335/https://www.itu.int/dms_pub/itu-r/oth/0a/0e/R0A0E0000960001PDFE.pdf|archive-date=5 September 2014}}</ref> and similar support for the redefinition was again expressed by Han, along with other Chinese timekeeping scientists, at the URSI General Assembly in 2014.

At a special session of the [[Asia-Pacific Telecommunity]] meeting on 10 February 2015, Chunhao Han indicated China was now supporting the elimination of future leap seconds, as were all the other presenting national representatives (from Australia, Japan, and the Republic of Korea).  At this meeting, Bruce Warrington (NMI, Australia) and Tsukasa Iwama (NICT, Japan) indicated particular concern for the financial markets due to the leap second occurring in the middle of a workday in their part of the world.{{efn|In addition to publishing the video of the special session,<ref>{{cite AV media|url=https://www.youtube.com/watch?v=gsyFp6G6iKo|title=Information Session on the WRC-15 agenda item 1.14 – Coordinated Universal Time (UTC)|date=15 April 2015|work=YouTube|url-status=live|archive-url=https://web.archive.org/web/20151118220255/https://www.youtube.com/watch?v=gsyFp6G6iKo|archive-date=18 November 2015}}</ref> the Australian Communications and Media Authority has a transcript of that session and a web page with draft content of the Conference Preparatory Meeting report and solutions for ITU-R WRC-15 Agenda Item 1.14.<ref>{{cite web|url=http://www.acma.gov.au/Industry/Spectrum/Spectrum-planning/International-planning-ITU-and-other-international-planning-bodies/wrc-15-agenda-item-114|archive-url=https://web.archive.org/web/20150908184107/http://www.acma.gov.au/Industry/Spectrum/Spectrum-planning/International-planning-ITU-and-other-international-planning-bodies/wrc-15-agenda-item-114|archive-date= 8 September 2015|url-status=dead|title=WRC-15 Agenda item 1.14: Coordinated Universal Time (UTC)|work=acma.gov.au}}</ref>}}  Subsequent to the CPM15-2 meeting in March/April 2015 the draft gives four methods which the WRC-15 might use to satisfy Resolution 653 from WRC-12.<ref>{{cite web|url=http://www.itu.int/dms_pub/itu-r/oth/0c/0a/R0C0A00000A0022PDFE.pdf|title=RESOLUTION 653 (WRC-12) Future of the Coordinated Universal Time time-scale|publisher=[[International Telecommunication Union]]|url-status=live|archive-url=https://web.archive.org/web/20150702175848/http://www.itu.int/dms_pub/itu-r/oth/0c/0a/R0C0A00000A0022PDFE.pdf|archive-date=2 July 2015}}</ref>

Arguments against the proposal include the unknown expense of such a major change and the fact that universal time will no longer correspond to mean solar time. It is also answered that two timescales that do not follow leap seconds are already available, [[International Atomic Time]] (<span title='Temps Atomique International' lang='fr'>TAI</span>) and [[Global Positioning System]] (GPS) time. Computers, for example, could use these and convert to UTC or local civil time as necessary for output. Inexpensive GPS timing receivers are readily available, and the satellite broadcasts include the necessary information to convert [[GPS time]] to UTC. It is also easy to convert GPS time to TAI, as TAI is always exactly 19 seconds ahead of GPS time. Examples of systems based on GPS time include the [[CDMA]] digital cellular systems [[IS-95]] and [[CDMA2000]]. In general, computer systems use UTC and synchronize their clocks using [[Network Time Protocol]] (NTP). Systems that cannot tolerate disruptions caused by leap seconds can base their time on TAI and use [[Precision Time Protocol]]. However, the BIPM has pointed out that this proliferation of timescales leads to confusion.<ref>{{citation|url=https://www.bipm.org/documents/20126/2071143/CCTF+Strategy.pdf/7cf0f648-2afe-d15c-0909-1f03406bbb8f|date=May 2016|title=CCTF Strategy Document|publisher=[[International Bureau of Weights and Measures]]|pages=21–25}}</ref>

At the 47th meeting of the Civil Global Positioning System Service Interface Committee in [[Fort Worth]], [[Texas]], in September 2007, it was announced that a mailed vote would go out on stopping leap seconds. The plan for the vote was:<ref>{{cite web|url=http://www.navcen.uscg.gov/pdf/cgsicMeetings/47/%5B16%5D%20CGSIC47-WL%20General_md.pdf|access-date=18 November 2007|date=25 September 2007|pages=9|title=47th CGSIC Meeting – Timing Subcommittee|url-status=dead|archive-url=https://web.archive.org/web/20110614015830/http://www.navcen.uscg.gov/pdf/cgsicMeetings/47/%5B16%5D%20CGSIC47-WL%20General_md.pdf|archive-date=14 June 2011}}</ref>
* April 2008: [[ITU]] Working Party 7A will submit to ITU Study Group 7 project recommendation on stopping leap seconds
* During 2008, Study Group 7 will conduct a vote through mail among member states
* October 2011: The ITU-R released its status paper, ''Status of Coordinated Universal Time (UTC) study in ITU-R'', in preparation for the January 2012 meeting in Geneva; the paper reported that, to date, in response to the UN agency's 2010 and 2011 web-based surveys requesting input on the topic, it had received 16 responses from the 192 Member States with "13 being in favor of change, 3 being contrary."<ref>{{cite journal|title=WP7D – Status of Coordinated Universal Time (UTC) study in ITU-R|journal=International Telecommunication Union – Radiocommunication Sector (ITU-R) Release|date=4 October 2011|page=2|url=http://www.itu.int/dms_pub/itu-r/oth/0A/08/R0A080000090001MSWE.docx|format=Word 2007|access-date=24 October 2011|quote=To date, the BR received replies from 16 different Member States for the latest survey (out of a total of 192 Member States, 55 of which participate in the formation of UTC) – 13 being in favor of the change, 3 being contrary.|url-status=live|archive-url=https://web.archive.org/web/20140323233615/http://www.itu.int/dms_pub/itu-r/oth/0A/08/R0A080000090001MSWE.docx|archive-date=23 March 2014}}</ref>
* January 2012: The ITU makes a decision.
In January 2012, rather than decide yes or no per this plan, the ITU decided to postpone a decision on leap seconds to the [[World Radiocommunication Conference]] in November 2015. At this conference, it was again decided to continue using leap seconds, pending further study and consideration at the next conference in 2023.<ref name=WRC>{{cite press release| title = Coordinated Universal Time (UTC) to retain 'leap second' | publisher = International Telecommunication Union | date = 19 November 2015| url = https://www.itu.int/net/pressoffice/press_releases/2015/53.aspx | url-status=dead<!--might be temporary? 18Nov22 (and 26May23)-->| archive-url = https://web.archive.org/web/20160129232825/https://www.itu.int/net/pressoffice/press_releases/2015/53.aspx | archive-date = 29 January 2016}}</ref>

In October 2014, Włodzimierz Lewandowski, chair of the timing subcommittee of the Civil GPS Interface Service Committee and a member of the ESA Navigation Program Board, presented a CGSIC-endorsed resolution to the ITU that supported the redefinition and described leap seconds as a "hazard to navigation".<ref>{{cite web|url=http://www.gps.gov/cgsic/timing/2014-resolution/|title=CGSIC opinion on the redefinition of UTC now under consideration by the International Telecommunication Union (ITU)|url-status=live|archive-url=https://web.archive.org/web/20141023113730/http://www.gps.gov/cgsic/timing/2014-resolution/|archive-date=23 October 2014}}</ref>

Some of the objections to the proposed change have been addressed by its supporters. For example, Felicitas Arias, who, as Director of the [[International Bureau of Weights and Measures]] (BIPM)'s Time, Frequency, and Gravimetry Department, was responsible for generating UTC, noted in a press release that the drift of about one minute every 60–90 years could be compared to the 16-minute annual variation between true solar time and mean solar time, the one hour offset by use of daylight time, and the several-hours offset in certain geographically extra-large time zones.<ref>{{cite press release|url=http://www.bipm.org/utils/en/pdf/Press_Release_UTC_13October.pdf|title=The proposed redefinition of Coordinated Universal Time, UTC|publisher=[[BIPM]]|date=13 October 2011|url-status=live|archive-url=https://web.archive.org/web/20150118133939/http://www.bipm.org/utils/en/pdf/Press_Release_UTC_13October.pdf|archive-date=18 January 2015}}</ref>

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>