It was already widely used in Italy by the 14th century and lasted until the mid-18th century; it was officially abolished in 1755, or in some regions customary until the mid-19th century. The system of Italian hours can be seen on a number of clocks in Europe, where the dial is numbered from 1 to 24 in either Roman or Arabic numerals.

However, scientific measurements eventually became precise enough to note the effect of tidal deceleration of the Earth by the Moon, which gradually lengthens the Earth's days. During the French Revolution, a general decimalisation of measures was enacted, including decimal time between 1793 and 1795.

However, scientific measurements eventually became precise enough to note the effect of tidal deceleration of the Earth by the Moon, which gradually lengthens the Earth's days. During the French Revolution, a general decimalisation of measures was enacted, including decimal time between 1793 and 1795.

This hour was only briefly in official use, being repealed by the same 1795 legislation that first established the metric system.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 Earth's rotation in AD1900.

The Thai system remains in informal use in the form codified in 1901 by King Chulalongkorn. ===India=== The Vedas and Puranas employed units of time based on the sidereal day (nakṣatra ahorātram).

Until 1968 Saudi Arabia used the system of counting 24 equal hours with the first hour starting at sunset. === Counting from noon === For many centuries, up to 1925, astronomers counted the hours and days from noon, because it was the easiest solar event to measure accurately.

This hour was only briefly in official use, being repealed by the same 1795 legislation that first established the metric system.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 Earth's rotation in AD1900.

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).

Until 1968 Saudi Arabia used the system of counting 24 equal hours with the first hour starting at sunset. === Counting from noon === For many centuries, up to 1925, astronomers counted the hours and days from noon, because it was the easiest solar event to measure accurately.

However, an hour of Coordinated Universal Time (UTC), used as the basis of most civil time, has lasted 3,601 seconds 27 times since 1972 in order to keep it within 0.9 seconds of universal time, which is based on measurements of the mean solar day at 0° longitude.

London: British Museum Press, 1996. == External links == World time zones Accurate time vs.

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