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24-hour clock | Definition, History, Uses, & Facts | Britannica

December 9, 2025

24-hour clock, time convention that begins the day at 00:00 and ends at 23:59, although 24:00 can be used to refer to 00:00 of the following day. The 24-hour clock is the international standard format for time (ISO 8601) and is currently the most widespread time notation worldwide.

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24-hour clock | Definition, History, Uses, & Facts | Britannica <body> <h1> Array ( [0] => 14-hour clock | definition, history, uses, & facts | britannica [1] => q4-hour clock | definition, history, uses, & facts | britannica [2] => w4-hour clock | definition, history, uses, & facts | britannica [3] => 34-hour clock | definition, history, uses, & facts | britannica [4] => 23-hour clock | definition, history, uses, & facts | britannica [5] => 2e-hour clock | definition, history, uses, & facts | britannica [6] => 2r-hour clock | definition, history, uses, & facts | britannica [7] => 25-hour clock | definition, history, uses, & facts | britannica [8] => 24=hour clock | definition, history, uses, & facts | britannica [9] => 240hour clock | definition, history, uses, & facts | britannica [10] => 24phour clock | definition, history, uses, & facts | britannica [11] => 24[hour clock | definition, history, uses, & facts | britannica [12] => 24-gour clock | definition, history, uses, & facts | britannica [13] => 24-bour clock | definition, history, uses, & facts | britannica [14] => 24-nour clock | definition, history, uses, & facts | britannica [15] => 24-jour clock | definition, history, uses, & facts | britannica [16] => 24-uour clock | definition, history, uses, & facts | britannica [17] => 24-your clock | definition, history, uses, & facts | britannica [18] => 24-hiur clock | definition, history, uses, & facts | britannica [19] => 24-hkur clock | definition, history, uses, & facts | britannica [20] => 24-hlur clock | definition, history, uses, & facts | britannica [21] => 24-hpur clock | definition, history, uses, & facts | britannica [22] => 24-h0ur clock | definition, history, uses, & facts | britannica [23] => 24-h9ur clock | definition, history, uses, & facts | britannica [24] => 24-hoyr clock | definition, history, uses, & facts | britannica [25] => 24-hohr clock | definition, history, uses, & facts | britannica [26] => 24-hojr clock | definition, history, uses, & facts | britannica [27] => 24-hoir clock | definition, history, uses, & facts | britannica [28] => 24-ho8r clock | definition, history, uses, & facts | britannica [29] => 24-ho7r clock | definition, history, uses, & facts | britannica [30] => 24-houe clock | definition, history, uses, & facts | britannica [31] => 24-houd clock | definition, history, uses, & facts | britannica [32] => 24-houf clock | definition, history, uses, & facts | britannica [33] => 24-hout clock | definition, history, uses, & facts | britannica [34] => 24-hou5 clock | definition, history, uses, & facts | britannica [35] => 24-hou4 clock | definition, history, uses, & facts | britannica [36] => 24-hour xlock | definition, history, uses, & facts | britannica [37] => 24-hour vlock | definition, history, uses, & facts | britannica [38] => 24-hour flock | definition, history, uses, & facts | britannica [39] => 24-hour dlock | definition, history, uses, & facts | britannica [40] => 24-hour dlock | definition, history, uses, & facts | britannica [41] => 24-hour ckock | definition, history, uses, & facts | britannica [42] => 24-hour cpock | definition, history, uses, & facts | britannica [43] => 24-hour coock | definition, history, uses, & facts | britannica [44] => 24-hour click | definition, history, uses, & facts | britannica [45] => 24-hour clkck | definition, history, uses, & facts | britannica [46] => 24-hour cllck | definition, history, uses, & facts | britannica [47] => 24-hour clpck | definition, history, uses, & facts | britannica [48] => 24-hour cl0ck | definition, history, uses, & facts | britannica [49] => 24-hour cl9ck | definition, history, uses, & facts | britannica [50] => 24-hour cloxk | definition, history, uses, & facts | britannica [51] => 24-hour clovk | definition, history, uses, & facts | britannica [52] => 24-hour clofk | definition, history, uses, & facts | britannica [53] => 24-hour clodk | definition, history, uses, & facts | britannica [54] => 24-hour clodk | definition, history, uses, & facts | britannica [55] => 24-hour clocj | definition, history, uses, & facts | britannica [56] => 24-hour clocm | definition, history, uses, & facts | britannica [57] => 24-hour clocl | definition, history, uses, & facts | britannica [58] => 24-hour cloco | definition, history, uses, & facts | britannica [59] => 24-hour cloci | definition, history, uses, & facts | britannica [60] => 24-hour clock | sefinition, history, uses, & facts | britannica [61] => 24-hour clock | xefinition, history, uses, & facts | britannica [62] => 24-hour clock | cefinition, history, uses, & facts | britannica [63] => 24-hour clock | fefinition, history, uses, & facts | britannica [64] => 24-hour clock | refinition, history, uses, & facts | britannica [65] => 24-hour clock | eefinition, history, uses, & facts | britannica [66] => 24-hour clock | dwfinition, history, uses, & facts | britannica [67] => 24-hour clock | dsfinition, history, uses, & facts | britannica [68] => 24-hour clock | ddfinition, history, uses, & facts | britannica [69] => 24-hour clock | drfinition, history, uses, & facts | britannica [70] => 24-hour clock | d4finition, history, uses, & facts | britannica [71] => 24-hour clock | d3finition, history, uses, & facts | britannica [72] => 24-hour clock | dedinition, history, uses, & facts | britannica [73] => 24-hour clock | decinition, history, uses, & facts | britannica [74] => 24-hour clock | devinition, history, uses, & facts | britannica [75] => 24-hour clock | deginition, history, uses, & facts | britannica [76] => 24-hour clock | detinition, history, uses, & facts | britannica [77] => 24-hour clock | derinition, history, uses, & facts | britannica [78] => 24-hour clock | defunition, history, uses, & facts | britannica [79] => 24-hour clock | defjnition, history, uses, & facts | britannica [80] => 24-hour clock | defknition, history, uses, & facts | britannica [81] => 24-hour clock | defonition, history, uses, & facts | britannica [82] => 24-hour clock | def9nition, history, uses, & facts | britannica [83] => 24-hour clock | def8nition, history, uses, & facts | britannica [84] => 24-hour clock | defibition, history, uses, & facts | britannica [85] => 24-hour clock | defimition, history, uses, & facts | britannica [86] => 24-hour clock | defijition, history, uses, & facts | britannica [87] => 24-hour clock | defihition, history, uses, & facts | britannica [88] => 24-hour clock | defihition, history, uses, & facts | britannica [89] => 24-hour clock | definution, history, uses, & facts | britannica [90] => 24-hour clock | definjtion, history, uses, & facts | britannica [91] => 24-hour clock | definktion, history, uses, & facts | britannica [92] => 24-hour clock | definotion, history, uses, & facts | britannica [93] => 24-hour clock | defin9tion, history, uses, & facts | britannica [94] => 24-hour clock | defin8tion, history, uses, & facts | britannica [95] => 24-hour clock | definirion, history, uses, & facts | britannica [96] => 24-hour clock | definifion, history, uses, & facts | britannica [97] => 24-hour clock | definigion, history, uses, & facts | britannica [98] => 24-hour clock | definiyion, history, uses, & facts | britannica [99] => 24-hour clock | defini6ion, history, uses, & facts | britannica [100] => 24-hour clock | defini5ion, history, uses, & facts | britannica [101] => 24-hour clock | definituon, history, uses, & facts | britannica [102] => 24-hour clock | definitjon, history, uses, & facts | britannica [103] => 24-hour clock | definitkon, history, uses, & facts | britannica [104] => 24-hour clock | definitoon, history, uses, & facts | britannica [105] => 24-hour clock | definit9on, history, uses, & facts | britannica [106] => 24-hour clock | definit8on, history, uses, & facts | britannica [107] => 24-hour clock | definitiin, history, uses, & facts | britannica [108] => 24-hour clock | definitikn, history, uses, & facts | britannica [109] => 24-hour clock | definitiln, history, uses, & facts | britannica [110] => 24-hour clock | definitipn, history, uses, & facts | britannica [111] => 24-hour clock | definiti0n, history, uses, & facts | britannica [112] => 24-hour clock | definiti9n, history, uses, & facts | britannica [113] => 24-hour clock | definitiob, history, uses, & facts | britannica [114] => 24-hour clock | definitiom, history, uses, & facts | britannica [115] => 24-hour clock | definitioj, history, uses, & facts | britannica [116] => 24-hour clock | definitioh, history, uses, & facts | britannica [117] => 24-hour clock | definitioh, history, uses, & facts | britannica [118] => 24-hour clock | definitionm history, uses, & facts | britannica [119] => 24-hour clock | definitionk history, uses, & facts | britannica [120] => 24-hour clock | definitionl history, uses, & facts | britannica [121] => 24-hour clock | definition. history, uses, & facts | britannica [122] => 24-hour clock | definition. history, uses, & facts | britannica [123] => 24-hour clock | definition, gistory, uses, & facts | britannica [124] => 24-hour clock | definition, bistory, uses, & facts | britannica [125] => 24-hour clock | definition, nistory, uses, & facts | britannica [126] => 24-hour clock | definition, jistory, uses, & facts | britannica [127] => 24-hour clock | definition, uistory, uses, & facts | britannica [128] => 24-hour clock | definition, yistory, uses, & facts | britannica [129] => 24-hour clock | definition, hustory, uses, & facts | britannica [130] => 24-hour clock | definition, hjstory, uses, & facts | britannica [131] => 24-hour clock | definition, hkstory, uses, & facts | britannica [132] => 24-hour clock | definition, hostory, uses, & facts | britannica [133] => 24-hour clock | definition, h9story, uses, & facts | britannica [134] => 24-hour clock | definition, h8story, uses, & facts | britannica [135] => 24-hour clock | definition, hiatory, uses, & facts | britannica [136] => 24-hour clock | definition, hiztory, uses, & facts | britannica [137] => 24-hour clock | definition, hixtory, uses, & facts | britannica [138] => 24-hour clock | definition, hidtory, uses, & facts | britannica [139] => 24-hour clock | definition, hietory, uses, & facts | britannica [140] => 24-hour clock | definition, hiwtory, uses, & facts | britannica [141] => 24-hour clock | definition, hisrory, uses, & facts | britannica [142] => 24-hour clock | definition, hisfory, uses, & facts | britannica [143] => 24-hour clock | definition, hisgory, uses, & facts | britannica [144] => 24-hour clock | definition, hisyory, uses, & facts | britannica [145] => 24-hour clock | definition, his6ory, uses, & facts | britannica [146] => 24-hour clock | definition, his5ory, uses, & facts | britannica [147] => 24-hour clock | definition, histiry, uses, & facts | britannica [148] => 24-hour clock | definition, histkry, uses, & facts | britannica [149] => 24-hour clock | definition, histlry, uses, & facts | britannica [150] => 24-hour clock | definition, histpry, uses, & facts | britannica [151] => 24-hour clock | definition, hist0ry, uses, & facts | britannica [152] => 24-hour clock | definition, hist9ry, uses, & facts | britannica [153] => 24-hour clock | definition, histoey, uses, & facts | britannica [154] => 24-hour clock | definition, histody, uses, & facts | britannica [155] => 24-hour clock | definition, histofy, uses, & facts | britannica [156] => 24-hour clock | definition, histoty, uses, & facts | britannica [157] => 24-hour clock | definition, histo5y, uses, & facts | britannica [158] => 24-hour clock | definition, histo4y, uses, & facts | britannica [159] => 24-hour clock | definition, histort, uses, & facts | britannica [160] => 24-hour clock | definition, historg, uses, & facts | britannica [161] => 24-hour clock | definition, historh, uses, & facts | britannica [162] => 24-hour clock | definition, historu, uses, & facts | britannica [163] => 24-hour clock | definition, histor7, uses, & facts | britannica [164] => 24-hour clock | definition, histor6, uses, & facts | britannica [165] => 24-hour clock | definition, historym uses, & facts | britannica [166] => 24-hour clock | definition, historyk uses, & facts | britannica [167] => 24-hour clock | definition, historyl uses, & facts | britannica [168] => 24-hour clock | definition, history. uses, & facts | britannica [169] => 24-hour clock | definition, history. uses, & facts | britannica [170] => 24-hour clock | definition, history, yses, & facts | britannica [171] => 24-hour clock | definition, history, hses, & facts | britannica [172] => 24-hour clock | definition, history, jses, & facts | britannica [173] => 24-hour clock | definition, history, ises, & facts | britannica [174] => 24-hour clock | definition, history, 8ses, & facts | britannica [175] => 24-hour clock | definition, history, 7ses, & facts | britannica [176] => 24-hour clock | definition, history, uaes, & facts | britannica [177] => 24-hour clock | definition, history, uzes, & facts | britannica [178] => 24-hour clock | definition, history, uxes, & facts | britannica [179] => 24-hour clock | definition, history, udes, & facts | britannica [180] => 24-hour clock | definition, history, uees, & facts | britannica [181] => 24-hour clock | definition, history, uwes, & facts | britannica [182] => 24-hour clock | definition, history, usws, & facts | britannica [183] => 24-hour clock | definition, history, usss, & facts | britannica [184] => 24-hour clock | definition, history, usds, & facts | britannica [185] => 24-hour clock | definition, history, usrs, & facts | britannica [186] => 24-hour clock | definition, history, us4s, & facts | britannica [187] => 24-hour clock | definition, history, us3s, & facts | britannica [188] => 24-hour clock | definition, history, usea, & facts | britannica [189] => 24-hour clock | definition, history, usez, & facts | britannica [190] => 24-hour clock | definition, history, usex, & facts | britannica [191] => 24-hour clock | definition, history, used, & facts | britannica [192] => 24-hour clock | definition, history, usee, & facts | britannica [193] => 24-hour clock | definition, history, usew, & facts | britannica [194] => 24-hour clock | definition, history, usesm & facts | britannica [195] => 24-hour clock | definition, history, usesk & facts | britannica [196] => 24-hour clock | definition, history, usesl & facts | britannica [197] => 24-hour clock | definition, history, uses. & facts | britannica [198] => 24-hour clock | definition, history, uses. & facts | britannica [199] => 24-hour clock | definition, history, uses, &zmp; facts | britannica [200] => 24-hour clock | definition, history, uses, &smp; facts | britannica [201] => 24-hour clock | definition, history, uses, &wmp; facts | britannica [202] => 24-hour clock | definition, history, uses, &qmp; facts | britannica [203] => 24-hour clock | definition, history, uses, &anp; facts | britannica [204] => 24-hour clock | definition, history, uses, &akp; facts | britannica [205] => 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definition, history, uses, & tacts | britannica [219] => 24-hour clock | definition, history, uses, & racts | britannica [220] => 24-hour clock | definition, history, uses, & fzcts | britannica [221] => 24-hour clock | definition, history, uses, & fscts | britannica [222] => 24-hour clock | definition, history, uses, & fwcts | britannica [223] => 24-hour clock | definition, history, uses, & fqcts | britannica [224] => 24-hour clock | definition, history, uses, & faxts | britannica [225] => 24-hour clock | definition, history, uses, & favts | britannica [226] => 24-hour clock | definition, history, uses, & fafts | britannica [227] => 24-hour clock | definition, history, uses, & fadts | britannica [228] => 24-hour clock | definition, history, uses, & fadts | britannica [229] => 24-hour clock | definition, history, uses, & facrs | britannica [230] => 24-hour clock | definition, history, uses, & facfs | britannica [231] => 24-hour clock | definition, history, uses, & facgs | britannica [232] => 24-hour clock | definition, history, uses, & facys | britannica [233] => 24-hour clock | definition, history, uses, & fac6s | britannica [234] => 24-hour clock | definition, history, uses, & fac5s | britannica [235] => 24-hour clock | definition, history, uses, & facta | britannica [236] => 24-hour clock | definition, history, uses, & factz | britannica [237] => 24-hour clock | definition, history, uses, & factx | britannica [238] => 24-hour clock | definition, history, uses, & factd | britannica [239] => 24-hour clock | definition, history, uses, & facte | britannica [240] => 24-hour clock | definition, history, uses, & factw | britannica [241] => 24-hour clock | definition, history, uses, & facts | vritannica [242] => 24-hour clock | definition, history, uses, & facts | nritannica [243] => 24-hour clock | definition, history, uses, & facts | hritannica [244] => 24-hour clock | definition, history, uses, & facts | gritannica [245] => 24-hour clock | definition, history, uses, & facts | gritannica [246] => 24-hour clock | definition, history, uses, & facts | beitannica [247] => 24-hour clock | definition, history, uses, & facts | bditannica [248] => 24-hour clock | definition, history, uses, & facts | bfitannica [249] => 24-hour clock | definition, history, uses, & facts | btitannica [250] => 24-hour clock | definition, history, uses, & facts | b5itannica [251] => 24-hour clock | definition, history, uses, & facts | b4itannica [252] => 24-hour clock | definition, history, uses, & facts | brutannica [253] => 24-hour clock | definition, history, uses, & facts | brjtannica [254] => 24-hour clock | definition, history, uses, & facts | brktannica [255] => 24-hour clock | definition, history, uses, & facts | brotannica [256] => 24-hour clock | definition, history, uses, & facts | br9tannica [257] => 24-hour clock | definition, history, uses, & facts | br8tannica [258] => 24-hour clock | definition, history, uses, & facts | brirannica [259] => 24-hour clock | definition, history, uses, & facts | brifannica [260] => 24-hour clock | definition, history, uses, & facts | brigannica [261] => 24-hour clock | definition, history, uses, & facts | briyannica [262] => 24-hour clock | definition, history, uses, & facts | bri6annica [263] => 24-hour clock | definition, history, uses, & facts | bri5annica [264] => 24-hour clock | definition, history, uses, & facts | britznnica [265] => 24-hour clock | definition, history, uses, & facts | britsnnica [266] => 24-hour clock | definition, history, uses, & facts | britwnnica [267] => 24-hour clock | definition, history, uses, & facts | britqnnica [268] => 24-hour clock | definition, history, uses, & facts | britabnica [269] => 24-hour clock | definition, history, uses, & facts | britamnica [270] => 24-hour clock | definition, history, uses, & facts | britajnica [271] => 24-hour clock | definition, history, uses, & facts | britahnica [272] => 24-hour clock | definition, history, uses, & facts | britahnica [273] => 24-hour clock | definition, history, uses, & facts | britanbica [274] => 24-hour clock | definition, history, uses, & facts | britanmica [275] => 24-hour clock | definition, history, uses, & facts | britanjica [276] => 24-hour clock | definition, history, uses, & facts | britanhica [277] => 24-hour clock | definition, history, uses, & facts | britanhica [278] => 24-hour clock | definition, history, uses, & facts | britannuca [279] => 24-hour clock | definition, history, uses, & facts | britannjca [280] => 24-hour clock | definition, history, uses, & facts | britannkca [281] => 24-hour clock | definition, history, uses, & facts | britannoca [282] => 24-hour clock | definition, history, uses, & facts | britann9ca [283] => 24-hour clock | definition, history, uses, & facts | britann8ca [284] => 24-hour clock | definition, history, uses, & facts | britannixa [285] => 24-hour clock | definition, history, uses, & facts | britanniva [286] => 24-hour clock | definition, history, uses, & facts | britannifa [287] => 24-hour clock | definition, history, uses, & facts | britannida [288] => 24-hour clock | definition, history, uses, & facts | britannida [289] => 24-hour clock | definition, history, uses, & facts | britannicz [290] => 24-hour clock | definition, history, uses, & facts | britannics [291] => 24-hour clock | definition, history, uses, & facts | britannicw [292] => 24-hour clock | definition, history, uses, & facts | britannicq ) </h1> </body>