The 24-hour clock, popularly referred to in the United States and some other countries as military time, [ 1 ] [ 2 ] is the convention of timekeeping in which the day runs from midnight to midnight and is divided into 24 hours. This is indicated by the hours passed since midnight, from 0 to 23. This arrangement is the most normally used time note in the world today, [ 1 ] and is used by the international standard ISO 8601. [ 3 ] A total of countries, peculiarly English-speaking, use the 12-hour clock, or a mix of the 24- and 12-hour prison term systems. In countries where the 12-hour clock is dominant, some professions prefer to use the 24-hour clock. For case, in the exercise of medicate, the 24-hour clock is broadly used in documentation of care as it prevents any ambiguity as to when events occurred in a affected role ‘s medical history. [ 4 ]
description [edit ]
24 hours
Reading: 24-hour clock – Wikipedia
24 hours ( 12 orally )
Both in common function
12 hours World map showing the custom of 12 or 24-hour clock in different countries A prison term of day is written in the 24-hour note in the form hh : millimeter ( for exemplar 01:23 ) or hh : millimeter : schutzstaffel ( for example, 01:23:45 ), where hh ( 00 to 23 ) is the count of full hours that have passed since midnight, millimeter ( 00 to 59 ) is the total of full minutes that have passed since the concluding full hour, and sulfur ( 00 to 59 ) is the numeral of seconds since the last full moment. In the case of a jump second, the value of s may extend to 60. A contribute zero is added for numbers under 10, but it is optional for the hours. The leading zero is identical normally used in computer applications, and always used when a specification requires it ( for case, ISO 8601 ). Where subsecond solution is required, the seconds can be a decimal fraction divide ; that is, the fractional part follows a decimal scatter or comma, as in 01:23:45.678. The most normally practice centrifuge symbol between hours, minutes and seconds is the colon, which is besides the symbol used in ISO 8601. In the past, some european countries used the department of transportation on the line as a centrifuge, but most national standards on time notation have since then been changed to the external standard colon. In some context ( including some computer protocols ), no centrifuge is used and times are written as, for example, “ 2359 ” .
Midnight 00:00 and 24:00 [edit ]
In the 24-hour time note, the day begins at midnight, 00:00, and the last minute of the day begins at 23:59. Where convenient, the note 24:00 may besides be used to refer to midnight at the end of a given date [ 5 ] — that is, 24:00 of one day is the lapp time as 00:00 of the follow day. The notation 24:00 chiefly serves to refer to the exact end of a day in a clock time interval. A distinctive use is giving opening hours ending at midnight ( e.g. “ 00:00–24:00 ”, “ 07:00–24:00 ” ). Similarly, some bus and train timetables show 00:00 as departure clock time and 24:00 as arrival time. Legal contracts much run from the startle date at 00:00 until the end date at 24:00. While the 24-hour notation unambiguously distinguishes between midnight at the beginning ( 00:00 ) and conclusion ( 24:00 ) of any given date, there is no normally accepted eminence among users of the 12-hour notation. Style guides and military communication regulations in some english-speaking countries discourage the use of 24:00 tied in the 24-hour note, and recommend reporting times about midnight as 23:59 or 00:01 alternatively. [ 6 ] sometimes the use of 00:00 is besides avoided. [ 6 ] In division with this, the correspondence manual for the United States Navy and United States Marine Corps once specified 0001 to 2400. [ 7 ] The manual was updated in June 2015 to use 0000 to 2359. [ 8 ]
Times after 24:00 [edit ]
Time-of-day notations beyond 24:00 ( such as 24:01 or 25:00 rather of 00:01 or 01:00 ) are not normally used and not covered by the relevant standards. however, they have been used occasionally in some special context in the United Kingdom, France, Spain, Canada, Japan, South Korea, Hong Kong, and China where business hours extend beyond midnight, such as circulate television production and schedule .
Computer defend [edit ]
In most countries, computers by default show the clock time in 24-hour notation. For exercise, Microsoft Windows and macOS activate the 12-hour notation by default only if a computer is in a handful of specific terminology and region settings. The 24-hour system is normally used in text-based interfaces. POSIX programs such as l default to displaying timestamps in 24-hour format.
military time [edit ]
In american English, the condition military time is a synonym for the 24-hour clock. [ 9 ] In the US, the clock time of day is customarily given about entirely using the 12-hour clock notation, which counts the hours of the day as 12, 1, …, 11 with suffixes a.m. and p.m. distinguishing the two diurnal repetitions of this sequence. The 24-hour clock is normally used there only in some specialist areas ( military, aviation, navigation, tourism, meteorology, astronomy, computing, logistics, emergency services, hospitals ), where the ambiguities of the 12-hour notation are deemed excessively inconvenient, cumbersome, or dangerous. military custom, as agreed between the United States and allied english-speaking military forces, [ 10 ] differs in some respects from other twenty-four-hour time systems :
history [edit ]
The 24-hour loom clock in Venice that lists hours 1 to 12 doubly The 24-hour clock system has its origins in the egyptian astronomic system of decans, and has been used for centuries by scientists, astronomers, navigators, and horologists. In East Asia, time notation was 24-hour before westernization in modern times. [ citation needed ] Western-made clocks were changed into 12 dual-hours style when they were shipped to China in the Qing dynasty. There are many surviving examples of clocks built using the 24-hour system, including the celebrated Orloj in Prague, and the Shepherd Gate Clock at Greenwich. [ citation needed ] The first mechanical public clocks introduced in Italy were mechanical 24-hour clocks which counted the 24 hours of the day from one-half hour after sunset to the evening of the adopt day. The 24th hour was the death hour of day time. [ 12 ] however, striking clocks had to produce 300 strokes each day, which required a distribute of r-2, 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 ). [ 12 ] After missing a train while travelling in Ireland in 1876 because a print agenda listed post meridiem alternatively of ante meridiem, Sir Sandford Fleming proposed a individual 24-hour clock for the entire worldly concern, located at the concentrate of the Earth, not linked to any surface meridian — a predecessor to Coordinated Universal Time. [ 13 ] [ 14 ] He was an early advocate of using the 24-hour clock as separate of a program to reform timekeeping, which besides included build time zones and a standard prime meridian. [ 15 ] The Canadian Pacific Railway was among the beginning organizations to adopt the 24-hour clock, at summer solstice 1886. [ 13 ] [ 16 ] At the International Meridian Conference in 1884, American lawyer and astronomer Lewis M. Rutherfurd proposed :
That this universal day is to be a think of solar day ; is to begin for all the world at the moment of midnight of the initial prime coincide with the beginning of the civil day and date of that acme, and is to be counted from zero up to twenty-four hours. [ 17 ]
This resolution was adopted by the league. [ 17 ]
A reputation by a government committee in the United Kingdom noted Italy as the first gear country among those mentioned to adopt 24-hour prison term nationally, in 1893. [ 18 ] 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 besides adopted the 24-hour clock. [ 19 ] Some of the railways in India had switched before the outbreak of the war. [ 18 ] During World War I, the british Royal Navy adopted the 24-hour clock in 1915, and the Allied armed forces followed soon after, [ 18 ] with the british Army switching formally in 1918. [ 20 ] The Canadian armed forces first started to use the 24-hour clock in late 1917. [ 21 ] In 1920, the United States Navy was the first United States constitution to adopt the system ; the United States Army, however, did not officially adopt the 24-hour clock until World War II, on July 1, 1942. [ 22 ]
A russian 24-hour watch for arctic expeditions from 1969, made by soviet watchmaker Raketa The use of the 24-hour clock in the United Kingdom has grown steadily since the begin of the twentieth century, although attempts to make the organization official failed more than once. [ 23 ] In 1934, the british Broadcasting Corporation ( BBC ) switched to the 24-hour clock for circulate announcements and course of study listings. The experiment was halted after five months following a miss of enthusiasm from the public, and the BBC continued using the 12-hour clock. [ 23 ] In the like year, Pan American World Airways Corporation and Western Airlines in the United States both adopted the 24-hour clock. [ 24 ] In modern times, the BBC uses a assortment of both the 12-hour and the 24-hour clock. [ 23 ] british Rail and London Transport switched to the 24-hour clock for timetables in 1964. [ 23 ] A concoction of the 12- and 24-hour clocks similarly prevails in other english-speaking Commonwealth countries : french speakers have adopted the 24-hour clock in Canada much more broadly than english speakers, and Australia besides uses both systems .