Editing Time zone (section)

== History ==
[[File:World time clock (multiple faces) 2.5m high.made in Dresden 1690, Technical Instrument Museum, Dresden.jpg|thumb|World time clock, 2.5&nbsp;m high. Made in [[Dresden]] 1690. Technical Instrument Museum, Dresden]]
The apparent position of the Sun in the sky, and thus [[solar time]], varies by location due to the [[spherical]] shape of the Earth. This variation corresponds to four [[minute]]s of time for every [[Degree (angle)|degree]] of [[longitude]], so for example when it is solar noon in [[London]], it is about 10 minutes before solar noon in [[Bristol]], which is about 2.5 degrees to the west.<ref>{{cite web |title=Latitude and Longitude of World Cities |url=http://www.infoplease.com/ipa/A0001769.html |publisher=Infoplease |access-date=April 18, 2012 |archive-date=May 24, 2011 |archive-url=https://web.archive.org/web/20110524213744/http://www.infoplease.com/ipa/A0001769.html |url-status=live }}</ref> Local solar time has been associated with civil timekeeping since the development of [[Sundial|sundials]]; c. 1500 BC, an [[Ancient Egypt|ancient Egyptian]] sundial was used to measure laborers' work hours.<ref>{{Cite web |title=One of world's oldest sun dial dug up in Kings' Valley, Upper Egypt |url=https://www.sciencedaily.com/releases/2013/03/130314085052.htm |access-date=2025-05-10 |website=ScienceDaily |language=en}}</ref> In the [[2nd century BC]], [[Hipparchus]] developed a method to measure longitudinal distances by comparing local solar times when a [[lunar eclipse]] was simultaneously observed at two locations. The work of Hipparchus is [[Lost literary work|lost]], but is known from citations in Strabo's Geographica, c. 7 AD.

The [[Royal Observatory, Greenwich]], founded in 1675, established [[Greenwich Mean Time]] (GMT), the mean solar time at that location, as an aid to mariners to determine longitude at sea, providing a standard reference time while each location in [[England]] kept a different time.

=== Railway time ===
{{Main|Railway time}}
[[File:Time zone chicago.jpg|thumb|right|upright|Plaque commemorating the Railway General Time Convention of 1883 in North America]]
[[File:Coventry Time Zone Clock.jpg|thumb|right|The control panel of the Time Zone Clock in front of [[Coventry Transport Museum]]]]

In the 19th century, as transportation and telecommunications improved, it became increasingly inconvenient for each location to observe its own solar time. In November 1840, the British [[Great Western Railway]] started using GMT kept by portable [[marine chronometer|chronometers]].<ref>{{Cite journal|date=December 1840|title=WESTMINSTER MEDICAL SOCIETY. Saturday, November 21, 1840.|url=http://dx.doi.org/10.1016/s0140-6736(00)59842-0|journal=The Lancet|volume=35|issue=901|pages=383|doi=10.1016/s0140-6736(00)59842-0|issn=0140-6736|access-date=January 27, 2021|archive-date=March 30, 2021|archive-url=https://web.archive.org/web/20210330010908/https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(00)59842-0/fulltext|url-status=live|url-access=subscription}}</ref>{{Failed verification|date=June 2023}} This practice was soon followed by other [[History of rail transport in Great Britain|railway companies in Great Britain]] and became known as [[railway time]].

Around August 23, 1852, time signals were first transmitted by [[telegraph]] from the Royal Observatory. By 1855, 98% of Great Britain's public clocks were using GMT, but it was not made the island's legal time until August 2, 1880. Some British clocks from this period have two minute hands, one for the local time and one for GMT.<ref>{{cite web |url=http://wwp.greenwichmeantime.com/info/bristol-time.htm |title=Bristol Time |work=GreenwichMeanTime.com |access-date=December 5, 2011 |archive-url=https://web.archive.org/web/20060628151049/http://wwp.greenwichmeantime.com/info/bristol-time.htm |archive-date=June 28, 2006 |url-status=dead }}</ref>

On November 2, 1868, the British [[Colony of New Zealand]] officially adopted a standard time to be observed throughout the colony.<ref>{{cite web|title=Telegraph line laid across Cook Strait.|url=https://nzhistory.govt.nz/page/submarine-telegraph-line-laid-across-cook-strait|publisher=New Zealand Ministry for Culture and Heritage|access-date=January 5, 2020|archive-date=February 18, 2020|archive-url=https://web.archive.org/web/20200218115412/https://nzhistory.govt.nz/page/submarine-telegraph-line-laid-across-cook-strait|url-status=live}}</ref> It was based on longitude {{nowrap|172°30′}} east of [[Greenwich]], that is 11 hours 30 minutes ahead of GMT. This standard was known as [[Time in New Zealand|New Zealand Mean Time]].<ref>{{cite web|title=Our Time. How we got it. New Zealand's Method. A Lead to the World.|url=http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&cl=search&d=EP19290408.2.88&srpos=2|work=Papers Past|publisher=Evening Post|access-date=October 2, 2013|page=10|archive-date=October 8, 2013|archive-url=https://web.archive.org/web/20131008192904/http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&cl=search&d=EP19290408.2.88&srpos=2|url-status=live}}</ref>
[[File:Time zone map of the United States 1913 (colorized).png|thumb|center|upright=1.6|1913 time zone map of the United States, showing boundaries very different from today]]

Timekeeping on [[North America]]n [[Rail transport|railroads]] in the 19th century was complex. Each railroad used its own standard time, usually based on the local time of its headquarters or most important terminus, and the railroad's train schedules were published using its own time. Some junctions served by several railroads had a clock for each railroad, each showing a different time.<ref>{{Cite magazine |url=https://www.wired.com/2010/11/1118railroad-time-zones/ |title=Nov. 18, 1883: Railroad Time Goes Coast to Coast |last=Alfred |first=Randy |date=November 18, 2010 |magazine=Wired |language=en-US |access-date=July 30, 2018 |archive-date=August 19, 2018 |archive-url=https://web.archive.org/web/20180819071241/https://www.wired.com/2010/11/1118railroad-time-zones/ |url-status=live }}</ref>  Because of this a number of accidents occurred when trains from different companies using the same tracks mistimed their passings.<ref>{{cite web |url=https://news.harvard.edu/gazette/story/2011/11/americas-first-time-zone/ |title=America's first time zone|date=November 10, 2011 }}</ref>

Around 1863, [[Charles F. Dowd]] proposed a system of hourly standard time zones for North American railroads, although he published nothing on the matter at that time and did not consult railroad officials until 1869. In 1870 he proposed four ideal time zones having north–south borders, the first centered on [[Washington, D.C.]], but by 1872 the first was centered on meridian [[75th meridian west|75° west of Greenwich]], with natural borders such as sections of the [[Appalachian Mountains]]. Dowd's system was never accepted by North American railroads. 
Chief meteorologist at the [[United States Weather Bureau]] [[Cleveland Abbe]] divided the United States into four standard time zones for consistency among the weather stations. In 1879, he published a paper titled ''Report on Standard Time''.<ref name=wws>{{harvnb|Debus|1968|p=2}}</ref> In 1883, he convinced North American railroad companies to adopt his time-zone system. In 1884, Britain, which had already adopted its own standard time system for England, Scotland, and Wales, helped gather international consent for global time. In time, the American government, influenced in part by Abbe's 1879 paper, adopted the time-zone system.<ref>{{harvnb|Asimov|1964|p=344}}</ref>
It was a version proposed by William F. Allen, the editor of the ''Traveler's Official Railway Guide''.<ref>{{cite web |url= http://bpp.wharton.upenn.edu/mawhite/Papers/TimeZones.pdf |title= Economics of Time Zones |url-status= dead |archive-url= https://web.archive.org/web/20120514014456/http://bpp.wharton.upenn.edu/mawhite/Papers/TimeZones.pdf |archive-date= May 14, 2012 }} &nbsp;{{small|(1.89&nbsp;MB)}}</ref> The borders of its time zones ran through railroad stations, often in major cities. For example, the border between its Eastern and Central time zones ran through [[Detroit]], [[Buffalo, New York|Buffalo]], [[Pittsburgh]], [[Atlanta]], and [[Charleston, South Carolina|Charleston]]. It was inaugurated on Sunday, November 18, 1883, also called "The Day of Two Noons",<ref>{{cite web |url=http://historymatters.gmu.edu/d/5748 |title=The ''Times'' Reports on "the Day of Two Noons" |work=History Matters |access-date=December 5, 2011 |archive-date=April 4, 2012 |archive-url=https://web.archive.org/web/20120404083446/http://historymatters.gmu.edu/d/5748 |url-status=live }}</ref> when each railroad station clock was reset as standard-time noon was reached within each time zone.

The North American zones were named Intercolonial, Eastern, Central, Mountain, and Pacific. Within a year 85% of all cities with populations over 10,000 (about 200 cities) were using standard time.<ref>{{cite web|url=http://www.sos.state.il.us/departments/archives/from_the_ashes/doc24.html |title=Resolution concerning new standard time by Chicago |publisher=Illinois Secretary of State |website=Illinois State Archives  |access-date=December 5, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20111005050317/http://www.sos.state.il.us/departments/archives/from_the_ashes/doc24.html |archive-date=October 5, 2011 }}</ref> A notable exception was Detroit (located about halfway between the meridians of Eastern and Central time), which kept local time until 1900, then tried Central Standard Time, [[local mean time]], and [[Eastern Time Zone|Eastern Standard Time]] (EST) before a May 1915 ordinance settled on EST and was ratified by popular vote in August 1916. The confusion of times came to an end when standard time zones were formally adopted by the [[United States Congress|U.S. Congress]] in the [[Standard Time Act]] of March 19, 1918.

=== Worldwide time zones ===
{{Redirect|World time|the global time standard|Universal Time}}
[[Italy|Italian]] mathematician [[Quirico Filopanti]] introduced the idea of a worldwide system of time zones in his book ''Miranda!'', published in 1858. He proposed 24 hourly time zones, which he called "longitudinal days", the first centred on the meridian of [[Rome]]. He also proposed a universal time to be used in astronomy and telegraphy. However, his book attracted no attention until long after his death.<ref>{{cite web |url=http://www.scienzagiovane.unibo.it/english/scientists/filopanti-1.html |title=Quirico Filopanti |website=scienzagiovane |publisher=Bologna University, Italy |archive-url=https://web.archive.org/web/20130117011106/http://www.scienzagiovane.unibo.it/english/scientists/filopanti-1.html |archive-date=January 17, 2013 |url-status=dead}}</ref><ref>{{cite web |title=Suggestions from... ...Gianluigi Parmeggiani, Osservatorio Astronomico di Bologna - The origin of time zones |url=http://www.iav.it/planetario/didastro/didastro/english.htm |website=Didastro |publisher=Istituti Aldini Valeriani e Sirani |archive-url=https://web.archive.org/web/20070824155341/http://www.iav.it/planetario/didastro/didastro/english.htm |archive-date=August 24, 2007 |url-status=dead}}</ref>

[[Scotland|Scottish]]-born [[Canada|Canadian]] Sir [[Sandford Fleming]] proposed a worldwide system of time zones in 1876 - see {{section link|Sandford Fleming|Inventor of worldwide standard time}}. The proposal divided the world into twenty-four time zones labeled A-Y (skipping J), each one covering 15 degrees of longitude. All clocks within each zone would be set to the same time as the others, but differed by one hour from those in the neighboring zones.<ref>{{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| access-date = March 24, 2022| archive-date = October 5, 2022| archive-url = https://web.archive.org/web/20221005110429/https://library.si.edu/digital-library/book/annualreportofbo18861smit| url-status = live}} Reprinted in 1889: {{Internet Archive|timereckoningfor00flem|''Time-reckoning for the twentieth century''}}.</ref> He advocated his system at several international conferences, including the [[International Meridian Conference]], where it received some consideration. The system has not been directly adopted, but some maps divide the world into 24 time zones and assign letters to them, similarly to Fleming's system.<ref>{{cite news |last1=Stromberg |first1=Joseph |title=Sandford Fleming Sets the World's Clock |url=https://www.smithsonianmag.com/smithsonian-institution/sandford-fleming-sets-the-worlds-clock-389930/ |work=Smithsonian Magazine |date=November 18, 2011 |language=en |access-date=March 24, 2022 |archive-date=March 24, 2022 |archive-url=https://web.archive.org/web/20220324012426/https://www.smithsonianmag.com/smithsonian-institution/sandford-fleming-sets-the-worlds-clock-389930/ |url-status=live }}</ref>

[[File:World Time Zone Chart 1942.jpg|thumb|400px|World map of time zones in 1928]]

By about 1900, almost all inhabited places on Earth had adopted a standard time zone, but only some of them used an hourly offset from GMT. Many applied the time at a local astronomical observatory to an entire country, without any reference to GMT. It took many decades before all time zones were based on some standard offset from GMT or [[Coordinated Universal Time]] (UTC). By 1929, the majority of countries had adopted hourly time zones, though some countries such as [[Iran]], [[India]], [[Myanmar]] and parts of [[Australia]] had time zones with a 30-minute offset. [[Nepal]] was the last country to adopt a standard offset, shifting slightly to UTC+05:45 in 1986.<ref>{{Cite web|title=Time Zone & Clock Changes in Kathmandu, Nepal|url=https://www.timeanddate.com/time/zone/nepal/kathmandu|access-date=December 1, 2020|website=timeanddate.com|language=en|archive-date=January 22, 2021|archive-url=https://web.archive.org/web/20210122042454/https://www.timeanddate.com/time/zone/nepal/kathmandu|url-status=live}}</ref>

All nations currently use standard time zones for secular purposes, but not all of them apply the concept as originally conceived. Several countries and subdivisions use half-hour or quarter-hour deviations from standard time. Some countries, such as [[China]] and [[India]], use a single time zone even though the extent of their territory far exceeds the ideal 15° of longitude for one hour; other countries, such as [[Spain]] and [[Argentina]], use standard hour-based offsets, but not necessarily those that would be determined by their geographical location. The consequences, in some areas, can affect the lives of local citizens, and in extreme cases contribute to larger political issues, such as in the western reaches of China.<ref>{{Cite news|url=https://www.theatlantic.com/china/archive/2013/11/china-only-has-one-time-zone-and-thats-a-problem/281136/|title=China Only Has One Time Zone—and That's a Problem|last=Schiavenza|first=Matt|date=November 5, 2013|work=The Atlantic|access-date=August 22, 2018|language=en-US|archive-date=August 22, 2018|archive-url=https://web.archive.org/web/20180822145736/https://www.theatlantic.com/china/archive/2013/11/china-only-has-one-time-zone-and-thats-a-problem/281136/|url-status=live}}</ref> In [[Time in Russia|Russia, which has 11 time zones]], two time zones were removed in 2010<ref>{{cite web|url=https://www.timeanddate.com/news/time/russia-reduces-time-zones.html|title=Russia Reduces Number of Time Zones|date=March 23, 2010|work=TimeAndDate.com|access-date=May 31, 2020|archive-date=August 9, 2020|archive-url=https://web.archive.org/web/20200809084135/https://www.timeanddate.com/news/time/russia-reduces-time-zones.html|url-status=live}}</ref><ref>{{cite web|title=About Time: Huge country, nine time zones|date=March 22, 2011|access-date=February 12, 2019|format=Video|website=[[BBC]]|language=en|url=https://www.bbc.com/news/av/world-europe-12809230/about-time-huge-country-nine-time-zones|archive-date=February 13, 2019|archive-url=https://web.archive.org/web/20190213012708/https://www.bbc.com/news/av/world-europe-12809230/about-time-huge-country-nine-time-zones|url-status=live}}</ref> and reinstated in 2014.<ref>{{cite news |title=Russian clocks to retreat again in winter, 11 time zones return |url=https://uk.reuters.com/article/us-russia-time/russian-clocks-to-retreat-again-in-winter-11-time-zones-return-idUSKBN0F64YB20140701 |website=Reuters |date=July 2014 |access-date=October 25, 2020 |archive-date=October 28, 2020 |archive-url=https://web.archive.org/web/20201028205217/https://uk.reuters.com/article/us-russia-time/russian-clocks-to-retreat-again-in-winter-11-time-zones-return-idUSKBN0F64YB20140701 |url-status=dead }}</ref>