Vatican II ordered their reformation for the Catholic Church in 1963, though they continue to be observed in the Orthodox churches. When mechanical clocks began to be used to show hours of daylight or nighttime, their period needed to be changed every morning and evening (for example, by changing the length of their pendula). The use of 24 hours for the entire day meant hours varied much less and the clocks needed to be adjusted only a few times a month. Modernity
The minor irregularities of the apparent solar day were smoothed by measuring time using the mean solar day, using the Suns movement along the celestial equator rather than along the ecliptic. The irregularities of this time system were so minor that most clocks reckoning such hours did not need adjustment. However, scientific measurements eventually became precise enough to note the effect of tidal deceleration of the Earth by the Moon, which gradually lengthens the Earths days. During the French Revolution, a general decimalisation of measures was enacted, including decimal time between 1793 and 1795. Under its provisions, the French hour (French: heure) was 1⁄10 of the day and divided formally into 100 decimal minutes (minute décimale) and informally into 10 tenths (décime). This hour was only briefly in official use, being repealed by the same 1795 legislation that first established the metric system. The metric system bases its measurements of time upon the second, defined since 1952 in terms of the Earths rotation in AD 1900.
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.