Two fire-spitting cobras were said to guard the gates of each hour of the underworld, and Wadjet and the rearing cobra (uraeus) were also sometimes referenced as wnwt from their role protecting the dead through these gates. The Egyptian word for astronomer, used as a synonym for priest, was wnwty, "one of the wnwt", as it were "one of the hours". The earliest forms of wnwt include one or three stars, with the later solar hours including the determinative hieroglyph for "sun". East Asia
Ancient China divided its day into 100 "marks" (Chinese: 刻, oc *kʰək, p kè) running from midnight to midnight. The system is said to have been used since remote antiquity, credited to the legendary Yellow Emperor, but is first attested in Han-era water clocks and in the 2nd-century history of that dynasty. It was measured with sundials and water clocks. Into the Eastern Han, the Chinese measured their day schematically, adding the 20-ke difference between the solstices evenly throughout the year, one every nine days. During the night, time was more commonly reckoned during the night by the "watches" (Chinese: 更, oc *kæŋ, p gēng) of the guard, which were reckoned as a fifth of the time from sunset to sunrise.Imperial China continued to use ke and geng but also began to divide the day into 12 "double hours" (t 時, s 时, oc *də, p shí, lit. "time[s]") named after the earthly branches and sometimes also known by the name of the corresponding animal of the Chinese zodiac.
An hour (symbol: h; also abbreviated hr) is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned between 3,599 and 3,601 seconds, depending on the speed of Earths rotation. There are 60 minutes in an hour, and 24 hours in a day. The hour was initially established in the ancient Near East as a variable measure of 1⁄12 of the night or daytime. Such seasonal, temporal, or unequal hours varied by season and latitude. Equal or equinoctial hours were taken as 1⁄24 of the day as measured from noon to noon; the minor seasonal variations of this unit were eventually smoothed by making it 1⁄24 of the mean solar day. Since this unit was not constant due to long term variations in the Earths rotation, the hour was finally separated from the Earths rotation and defined in terms of the atomic or physical second. In the modern metric system, hours are an accepted unit of time defined as 3,600 atomic seconds. However, on rare occasions an hour may incorporate a positive or negative leap second, making it last 3,599 or 3,601 seconds, in order to keep it within 0.9 seconds of UT1, which is based on measurements of the mean solar day. Name
Hour is a development of the Anglo-Norman houre and Middle English ure, first attested in the 13th century.It displaced tide tīd, "time" and stound stund, span of time.