Editing 24-hour clock (section)

== History ==
[[File:Florence-Duomo-Clock.jpg|thumb|[[Paolo Uccello]]'s ''Face with Four Prophets/Evangelists'' (1443) in [[Florence Cathedral]]]]
[[File:Clock 24 J.jpg|thumb|The 24-hour tower clock in [[Venice]] that lists hours 1 to 12 twice]]
The first mechanical public clocks introduced in Italy were [[24-hour analogue dial|mechanical 24-hour clocks]] which counted the 24 hours of the day from one-half hour after sunset to the evening of the following day. The 24th hour was the last hour of day time.<ref name="Rossum">{{Cite book |last=Dohrn-Van Rossum |first=Gerhard |date=1996 |title=History of the Hour. Clock and Modern Temporal Orders |publisher=The University of Chicago Press |page=114 |isbn=0226155110}}</ref>

From the 14th to the 17th century, two systems of time measurement competed in Europe:<ref>Tomáš Voříšek: [http://otta.cechove.cz/hodiny.htm Hodiny německé a české na půl orloje a podle celého orloje], Otta z Losu, last update 2021.</ref><ref>Stan. Marušák, Petr Král: [https://www.orloj.eu/cs/orloj_ctyriadvacetnik.htm Čtyřiadvacetník], Orloj.eu.</ref>
* Italian (Bohemian, Old-Bohemian) hours (full-dial): 24 hours system with the day starting after sunset; on the static dial, the 24th hour was on the right side. In Italy, it was prevalently modified to a 4×6 hours system, but some 24-hour dials lasted until the 19th century. The system has spread especially to the Alpine countries, Czech countries and Poland. In Bohemia, this system was finally banned in 1621 after the [[Battle of White Mountain|defeat on White Mountain]]. The Prague Astronomical Clock struck according to the Old Bohemian Clock until its destruction in 1945. The variant with counting from dawn is also rarely documented and used, e.g. on a 16th-century cabinet clock in the Vienna Art-History Museum.<ref>[https://www.orloj.eu/cs/cesky_cas.htm Český čas s otazníkem], Orloj.eu.</ref>
* German (Gallic) hours (half-dial): 2×12 hour system starting at midnight and restarted at noon. It is typical with the 12-hour dial with 12 at the top. 
The modern 24-hour system is a late-19th century adaptation of the German midnight-starting system, and then prevailed in the world with the exception of some Anglophone countries.

Striking clocks had to produce 300 strokes each day, which required a lot of rope, and wore out the mechanism quickly, so some localities switched to ringing sequences of 1 to 12 twice (156 strokes), or even 1 to 6 repeated four times (84 strokes).<ref name="Rossum" />

[[Sandford Fleming]], the engineer-in-chief of the Canadian [[Intercolonial Railway]], was an early proponent of using the 24-hour clock as part of a programme to reform timekeeping, which also included establishing [[time zone]]s and a standard [[prime meridian]].<ref name="Fleming">{{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}} Reprinted in 1889: {{Internet Archive|timereckoningfor00flem|''Time-reckoning for the twentieth century''}}.</ref><ref name="Creet">{{Cite journal |last1=Creet |first1=Mario |title=Sandford Fleming and Universal Time |journal=Scientia Canadensis: Canadian Journal of the History of Science, Technology and Medicine |date=1990 |volume=14 |issue=1–2 |pages=66–89 |doi=10.7202/800302ar|doi-access=free }}</ref> At the [[International Meridian Conference]] in 1884, the following resolution was adopted by the conference:<ref name=imc />
{{blockquote|
That this universal day is to be a mean solar day; is to begin for all the world at the moment of midnight of the initial meridian coinciding with the beginning of the civil day and date of that meridian, and is to be counted from zero up to twenty-four hours.<ref name=imc>{{Cite web|title=International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day. October 1884. Protocols of the proceedings.|url=http://www.gutenberg.org/files/17759/17759-h/17759-h.htm|publisher=Project Gutenberg|access-date=30 November 2012|year=1884}}</ref>
}}

[[File:Greenwich clock 1-manipulated.jpg|thumb|The [[Shepherd Gate Clock]] with [[Roman numerals]] up to XXIII (23) and 0 for midnight, in Greenwich]]
The [[Canadian Pacific Railway]] was among the first organisations to adopt the 24-hour clock, at [[midsummer]] 1886.<ref name="Fleming" /><ref>The London ''[[The Times|Times]]'' reports on a timetable using the 24-hour clock on a trip from [[Port Arthur, Ontario]]: {{Cite newspaper The Times |title= A Canadian Tour |date= 2 October 1886 |page=8 |issue=31880 |column=1–2}}</ref> A report by a government committee in the United Kingdom noted Italy as the first country among those mentioned to adopt 24-hour time nationally, in 1893.<ref name="baird">{{Cite web|url=http://discovery.nationalarchives.gov.uk/details/r/D7736214|title=Memorandum CAB 24/110/21 (CP 1721), 'Report of the Committee upon the 24 hour method of expressing time'|date=4 August 1920|location=[[The National Archives (United Kingdom)|The National Archives]], [[Kew]], [[United Kingdom]]}}</ref> Other European countries followed: France adopted it in 1912 (the French army in 1909), followed by Denmark (1916), and Greece (1917). By 1920, Spain, Portugal, Belgium, and Switzerland had switched, followed by Turkey (1925), and Germany (1927). By the early 1920s, many countries in Latin America had also adopted the 24-hour clock.<ref>{{Cite web|url=https://militarytimechart.net/history-24-hour-clock/|website=Military Time Chart|title=History of the 24-Hour Clock - 24 Hour Time Clock|date=24 December 2016|accessdate=27 July 2023}}</ref> Some of the railways in India had switched before the outbreak of the war.<ref name="baird" />

During [[World War I]], the British Royal Navy adopted the 24-hour clock in 1915, and the Allied armed forces followed soon after,<ref name="baird" /> with the British Army switching officially in 1918.<ref>''[[The Times]]'': 1918 September 19, p. 3.</ref> The Canadian armed forces first started to use the 24-hour clock in late 1917.<ref>Dancocks, Daniel G. ''Gallant Canadians: The Story of the 10th Canadian Infantry Battalion 1914–1919''.</ref> In 1920, the United States Navy was the first United States organisation to adopt the system; the [[United States Army]], however, did not officially adopt the 24-hour clock until 1 July 1942.<ref name="BrownsvilleHerald1942">{{cite news |title=Army Adopts 24-Hour Clock Plan |newspaper=Brownsville Herald |location=[[Brownsville, Texas]] |date=26 June 1942 |page=2 |url=https://newspaperarchive.com/us/texas/brownsville/brownsville-herald/1942/06-26/page-2/ |quote=Effective July 1, the United States Army will adopt the 24-hour clock system for all messages, dispatches, orders and reports, the War Department has announced. Under this new system time will be expressed in a group of four digits ranging from 0000 to 2400. [...] Flying officers at [[Moore Air Force Base|Moore Field]] have used the 24-hour clock system for some time. However, its use in official business messages will be an innovation.}}</ref>
<ref name="ElPaso1942">{{cite news |title=It Will Be 2100 O'Clock at Ft. Bliss At 3 p. m. |newspaper=El Paso Herald-Post |location=[[El Paso]] |date=3 July 1942 |page=3 |url=https://newspaperarchive.com/us/texas/el-paso/el-paso-herald-post/1942/07-03/page-3/ |quote=The Army has a new time system — Greenwich Civil Time — to be used in radiograms, telegrams, and all official communications. [...] Effective 10 p. m. Monday, the War Department adopted the 24-hour system, which is used internationally with the Navy and the Armed forces of associated nations. [...] the six hours difference between Mountain War Time and actual Greenwich time must be taken into account, so that 12 noon is expressed on communications as 1800.}}</ref>

The use of the [[Date and time notation in the United Kingdom#Time|24-hour clock in the United Kingdom]] has grown steadily since the beginning of the 20th century, although attempts to make the system official failed more than once.<ref name="counting-time">{{Cite book |last=Boardman |first=Peter |date=July 2011 |url=http://clock24.nfshost.com/counting-time.html |title=Counting Time: a brief history of the 24-hour clock}}{{Self-published source|date=September 2014}}</ref> In 1934, the [[BBC|British Broadcasting Corporation]] (BBC) switched to the 24-hour clock for broadcast announcements and programme listings. The experiment was halted after five months following a lack of enthusiasm from the public, and the BBC continued using the 12-hour clock.<ref name="counting-time" /> In the same year, [[Pan American World Airways|Pan American World Airways Corporation]] and [[Western Airlines]] in the United States both adopted the 24-hour clock.<ref>Sarasota Herald-Tribune 1943 May 14.</ref> In modern times, the BBC uses a mixture of both the 12-hour and the 24-hour clock.<ref name="counting-time" /> [[British Rail]], [[London Transport (brand)|London Transport]], and the [[London Underground]] switched to the 24-hour clock for timetables in 1964.<ref name="counting-time" /> A mixture of the 12- and 24-hour clocks similarly prevails in other English-speaking [[Commonwealth of Nations|Commonwealth]] countries: French speakers have adopted the [[Date and time notation in Canada#Time|24-hour clock in Canada]] much more broadly than English speakers, and [[Date and time notation in Australia#Time|Australia]] as well as New Zealand also use both systems.