Editing Daylight saving time (section)

==Procedure==
{{See also|Daylight saving time by country}}
{{multiple image|align= left|direction= vertical|width= 165|image1= Begin CEST.svg|alt1= Diagram of a clock showing a transition from 02:00 to 03:00|caption1= When DST observation begins, clocks are advanced by one hour during the very early morning.|image2= End CEST.svg|alt2= Diagram of a clock showing a transition from 03:00 to 02:00|caption2= When DST observation ends and standard time observation resumes, clocks are turned back one hour during the very early morning.<br><br>Specific times of the clock change vary by jurisdiction.}}

The relevant authorities typically schedule clock changes to occur at (or soon after) [[midnight]] and on a weekend, in order to lessen disruption to weekday schedules.<ref>{{cite web |title= Information for visitors |url= http://www.lordhoweisland.info/important-info.htm |publisher= Lord Howe Island Tourism Association |access-date= 20 April 2009 |url-status=dead |archive-url= https://web.archive.org/web/20090503074945/http://www.lordhoweisland.info/important-info.htm |archive-date= 3 May 2009}}</ref> A one-hour change is usual, but twenty-minute and two-hour changes have been used in the past. Notable exceptions today include [[Lord Howe Island]] with a thirty-minute change, and [[Troll (research station)]] that shifts two hours directly between CEST and GMT since 2016.<ref>{{cite web|url=https://www.timeanddate.com/time/zone/antarctica/troll|title=Time Zone & Clock Changes in Troll Station, Antarctica|website=timeanddate.com|accessdate=18 October 2023}}</ref>
In all countries that observe daylight saving time seasonally (i.e., during summer and not winter), the clock is advanced from standard time to daylight saving time in the spring, and it is turned back from daylight saving time to standard time in the autumn.

For a midnight change in spring, a digital display of local time would appear to jump from 23:59:59.9 to 01:00:00.0. For the same clock in autumn, the local time would appear to repeat the hour preceding midnight, i.e. it would jump from 23:59:59.9 to 23:00:00.0.

In most countries that observe seasonal daylight saving time, clocks revert in winter to [[standard time]].<ref>{{citation |title=Time Zone Abbreviations – Worldwide List |url=https://www.timeanddate.com/time/zones/ |website=timeanddate.com |access-date=14 May 2020 |archive-date=21 August 2018 |archive-url=https://web.archive.org/web/20180821101900/https://www.timeanddate.com/time/zones/ |url-status=live }}</ref><ref>{{cite web |last1=MacRobert |first1=Alan |title=Time in the Sky and the Amateur Astronomer |date=18 July 2006 |url=https://skyandtelescope.org/astronomy-resources/time-in-the-sky-and-the-amateur-astronomer/ |publisher=Sky and Telescope |access-date=14 May 2020 |archive-date=11 July 2020 |archive-url=https://web.archive.org/web/20200711064657/https://skyandtelescope.org/astronomy-resources/time-in-the-sky-and-the-amateur-astronomer/ |url-status=live }}</ref> An exception exists in Ireland, where its winter clock has the same offset ([[UTC+00:00]]) and legal name as that in Britain ([[Greenwich Mean Time]])—but while its summer clock also has the same offset as Britain's ([[UTC+01:00]]), its legal name is confusingly called Irish ''Standard'' Time<ref>{{cite web |title=Standard Time (Amendment) Act, 1971, Section 1 |url=http://www.irishstatutebook.ie/eli/1971/act/17/section/1/enacted/en/html |website=electronic Irish Statute Book |language=en |access-date=3 June 2019 |archive-date=30 October 2013 |archive-url=https://web.archive.org/web/20131030172404/http://www.irishstatutebook.ie/1971/en/act/pub/0017/sec0001.html |url-status=live }}</ref><ref>{{cite web |title=Time Zones in Ireland |url=https://www.timeanddate.com/time/zone/ireland |website=timeanddate.com |access-date=14 May 2020 |archive-date=31 December 2019 |archive-url=https://web.archive.org/web/20191231223351/https://www.timeanddate.com/time/zone/ireland |url-status=live }}</ref> as opposed to [[British Summer Time]].<ref>{{cite web |title=Time Zones in the United Kingdom |url=https://www.timeanddate.com/time/zone/uk |website=timeanddate.com |access-date=14 May 2020 |archive-date=8 July 2020 |archive-url=https://web.archive.org/web/20200708023651/https://www.timeanddate.com/time/zone/uk |url-status=live }}</ref>

Since 2019, [[Time in Morocco|Morocco]] observes daylight saving time every month but [[Ramadan (calendar month)|Ramadan]]. During the holy month (the date of which is determined by the [[lunar calendar]] and thus moves annually with regard to the [[Gregorian calendar]]), the country's civil clocks observe [[Western European Time]] (UTC+00:00, which geographically overlaps most of the nation). At the close of that month, its clocks are turned forward to [[Western European Summer Time]] (UTC+01:00).<ref>{{cite news |last1=Kasraoui |first1=Safaa |title=Morocco to Switch Clocks Back 1 Hour on May 5 for Ramadan |url=https://www.moroccoworldnews.com/2019/04/270773/morocco-gmt-dst-ramadan/ |work=Morocco World News |date=16 April 2019 |access-date=5 June 2019 |archive-date=5 June 2019 |archive-url=https://web.archive.org/web/20190605064137/https://www.moroccoworldnews.com/2019/04/270773/morocco-gmt-dst-ramadan/ |url-status=live }}</ref><ref name="sgg.gov 2018">{{cite press release |title=Release of the Moroccan Official Journal |url=http://www.sgg.gov.ma/Portals/1/BO/2018/BO_6720-bis_Ar.pdf?ver=2018-10-27-101217-477 |language=ar |access-date=31 October 2018 |archive-url=https://web.archive.org/web/20191026141815/http://www.sgg.gov.ma/Portals/1/BO/2018/BO_6720-bis_Ar.pdf?ver=2018-10-27-101217-477 |archive-date=26 October 2019}}</ref><ref>{{cite web |title=Time Zones in Morocco |url=https://www.timeanddate.com/time/zone/morocco |website=timeanddate.com |access-date=15 May 2020 |archive-date=27 June 2020 |archive-url=https://web.archive.org/web/20200627003422/https://www.timeanddate.com/time/zone/morocco |url-status=live }}</ref>

The time at which to change clocks differs across jurisdictions. Members of the [[European Union]] conduct a coordinated change, changing all zones at the same instant, at 01:00 [[Coordinated Universal Time]] (UTC), which means that it changes at 02:00 [[Central European Time]] (CET), equivalent to 03:00 [[Eastern European Time]] (EET). As a result, the time differences across European time zones remain constant.<ref>{{cite web|url= http://www.npl.co.uk/reference/faqs/at-what-time-should-clocks-go-forward-or-back-for-summer-time-faq-time|last= National Physical Laboratory|title= At what time should clocks go forward or back for summer time (FAQ – Time)|date= 31 March 2016|access-date= 17 October 2016|quote= The time at which summer time begins and ends is given in the relevant EU Directive and UK Statutory Instrument as 1&nbsp;am. Greenwich Mean Time (GMT)... All time signals are based on Coordinated Universal Time (UTC), which can be almost one second ahead of, or behind, GMT so there is a brief period in the UK when the directive is not being strictly followed.|archive-url= https://web.archive.org/web/20161011093001/http://www.npl.co.uk/reference/faqs/at-what-time-should-clocks-go-forward-or-back-for-summer-time-faq-time|archive-date= 11 October 2016|url-status=dead}}</ref><ref name=Myers /> North America coordination of the clock change differs, in that each jurisdiction changes at each local clock's 02:00, which temporarily creates an imbalance with the next time zone (until it adjusts its clock, one hour later, at 2 am there). For example, [[Mountain Time Zone|Mountain Time]] is for one hour in the spring two hours ahead of [[Pacific Time Zone|Pacific Time]] instead of the usual one hour ahead, and instead of one hour in the autumn, briefly zero hours ahead of Pacific Time.

The dates on which clocks change vary with location and year; consequently, the time differences between regions also vary throughout the year. For example, [[Paris]] (which uses Central European Time) is usually six hours ahead of [[New York City]] (which uses [[Eastern Time Zone|North American Eastern Time]]), except for a few weeks in March and October/November when it is five hours ahead.  Paris and [[Santiago]] are six hours apart during the northern summer, four hours during the southern summer, and five hours for a few weeks per year. Since 1996, [[Summer time in Europe|European Summer Time]] has been observed from the last Sunday in March to the last Sunday in October; previously the rules were not uniform across the European Union.<ref name=Myers /> Starting in 2007, most of the United States and Canada observed DST from the second Sunday in March to the first Sunday in November, almost two-thirds of the year.<ref>{{cite news |author= Tom Baldwin |date= 12 March 2007 |url= https://www.thetimes.com/uk/environment/article/us-gets-summertime-blues-as-the-clocks-go-forward-3-weeks-early-d5rjglj28bx |title= US gets summertime blues as the clocks go forward 3 weeks early |work= [[The Times]] |location= London |access-date= 2 November 2018 |archive-date= 2 April 2019 |archive-url= https://web.archive.org/web/20190402042747/https://www.thetimes.co.uk/article/us-gets-summertime-blues-as-the-clocks-go-forward-3-weeks-early-d5rjglj28bx |url-status= live }}</ref> Moreover, the beginning and ending dates are roughly reversed between the northern and southern hemispheres because spring and autumn are displaced six months. For example, mainland Chile observes DST from the second Saturday in October to the second Saturday in March, with transitions at the local clock's [[24-hour clock#Midnight 00:00 and 24:00|24:00]].<ref>{{cite web |title= Historia Hora Oficial de Chile |date= 1 October 2008 |publisher= Chilean Hydrographic and Oceanographic Service |language= es |url= http://www.horaoficial.cl/historia_hora.html |access-date= 15 November 2014 |archive-date= 2 April 2019 |archive-url= https://web.archive.org/web/20190402042725/http://www.horaoficial.cl/historia_hora.html |url-status= live }}</ref> In some countries, clocks are governed by regional jurisdictions within the country such that some jurisdictions change and others do not; this is currently the case in Australia, Canada, and the United States.{{sfnp|''Seize the Daylight''|2005|pp=179–180}}<ref>{{cite news|url= https://www.usatoday.com/story/news/nation-now/2017/03/09/arizona-no-daylight-saving-time/98964644/|title= Why Arizona doesn't observe daylight-saving time|newspaper= [[USA Today]]|access-date= 26 August 2017|archive-date= 30 March 2019|archive-url= https://web.archive.org/web/20190330084430/https://www.usatoday.com/story/news/nation-now/2017/03/09/arizona-no-daylight-saving-time/98964644/|url-status= live}}</ref>

From year to year, the dates on which to change clock may also move for political or social reasons. The [[Uniform Time Act of 1966]] formalized the United States' period of daylight saving time observation as lasting six months (it was previously declared locally); this period was extended to seven months in 1986, and then to eight months in 2005.<ref name="Downing 2018">{{cite news |last1=Downing |first1=Michael |title=One Hundred Years Later, the Madness of Daylight Saving Time Endures |url=http://theconversation.com/100-years-later-the-madness-of-daylight-saving-time-endures-93048 |access-date=14 May 2020 |publisher=The Conversation |date=2018 |archive-date=19 February 2020 |archive-url=https://web.archive.org/web/20200219193534/http://theconversation.com/100-years-later-the-madness-of-daylight-saving-time-endures-93048 |url-status=live }}</ref><ref name="Korch 2015">{{cite news |last1=Korch |first1=Travers |title=The Financial History of Daylight Saving |url=http://www.bankrate.com/finance/personal-finance/financial-history-daylight-saving-1.aspx |access-date=14 May 2020 |publisher=Bankrate |date=2015 |archive-date=11 July 2020 |archive-url=https://web.archive.org/web/20200711014802/https://www.bankrate.com/finance/personal-finance/financial-history-daylight-saving-1.aspx |url-status=live }}</ref><ref>{{cite web |title= Energy Policy Act of 2005, Public Law 109-58 §&nbsp;110 |url= http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=109_cong_public_laws&docid=f:publ058.109 |date= 8 August 2005 |access-date= 11 July 2007 |archive-date= 16 July 2009 |archive-url= https://web.archive.org/web/20090716041640/http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=109_cong_public_laws&docid=f:publ058.109 |url-status= live }}</ref> The 2005 extension was motivated in part by lobbyists from the candy industry, seeking to increase profits by including [[Halloween]] (31 October) within the daylight saving time period.<ref>{{cite news |last1=Morgan |first1=Thad |title=The Sweet Relationship Between Daylight Saving Time and Halloween |url=http://www.history.com/news/the-sweet-relationship-between-daylight-saving-time-and-halloween |access-date=14 May 2020 |publisher=History |date=2017 |ref=Morgan 2017 |archive-date=12 May 2020 |archive-url=https://web.archive.org/web/20200512163136/http://www.history.com/news/the-sweet-relationship-between-daylight-saving-time-and-halloween |url-status=dead }}</ref> In recent history, Australian state jurisdictions not only changed at different local times but sometimes on different dates. For example, in 2008 most states there that observed daylight saving time changed clocks forward on 5 October, but [[Western Australia]] changed on 26 October.<ref>{{cite web |url= http://www.bom.gov.au/climate/averages/tables/dst_times.shtml |title= Implementation dates of daylight saving time within Australia |publisher= Bureau of Meteorology |date= 22 September 2009 |access-date= 11 July 2007 |archive-date= 4 April 2016 |archive-url= https://web.archive.org/web/20160404124201/http://www.bom.gov.au/climate/averages/tables/dst_times.shtml |url-status= live }}</ref>