Hours Of Work Vs

An hour (symbol: h; also abbreviated hr) is a unit of time conventionally reckoned as of a day and scientifically reckoned between 3,599 and 3,601 seconds, depending on the speed of Earth's 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 of the night or daytime. Such seasonal, temporal, or unequal hours varied by season and latitude.

Equal or equinoctial hours were taken as of the day as measured from noon to noon; the minor seasonal variations of this unit were eventually smoothed by making it of the mean solar day. Since this unit was not constant due to long term variations in the Earth's rotation, the hour was finally separated from the Earth's 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 ' and Middle English ', first attested in the 13th century.

It displaced tide tīd, "time" and stound stund, ''span of time''. The Anglo-Norman term was a borrowing of Old French ', a variant of ', which derived from Latin ' and Greek ''hṓrā'' ().

Like Old English ' and ', ''hṓrā'' was originally a vaguer word for any span of time, including seasons and years. Its Proto-Indo-European root has been reconstructed as ' ("year, summer"), making ''hour'' distantly cognate with ''year''.

The time of day is typically expressed in English in terms of hours. Whole hours on a 12-hour clock are expressed using the contracted phrase ''o'clock'', from the older ''of the clock''. (10 am and 10 pm are both read as "ten o'clock".)

Hours on a 24-hour clock ("military time") are expressed as "hundred" or "hundred hours". (1000 is read "ten hundred" or "ten hundred hours"; 10 pm would be "twenty-two hundred".)

Fifteen and thirty minutes past the hour is expressed as "a quarter past" or "after" and "half past", respectively, from their fraction of the hour. Fifteen minutes before the hour may be expressed as "a quarter to", "of", "till", or "before" the hour. (9:45 may be read "nine forty-five" or "a quarter till ten".)

History

Antiquity

The ancient Greeks kept time differently from the way we do today. Instead of dividing the time between one midnight and the next into 24 equal hours, they divided the time from sunrise to sunset into 12 "seasonal hours" (their actual duration depending on season), and the time from sunset to the next sunrise again in 12 "seasonal hours". Initially, only the day was divided into 12 seasonal hours and the night into 3 or 4 night watches.

By the Hellenistic period the night was also divided into 12 hours. The day-and-night () was probably first divided into twenty-four hours by Hipparchus of Nicaea. The Greek astronomer Andronicus of Cyrrhus oversaw the construction of a horologion called the Tower of the Winds in Athens during the first century BCE. This structure tracked a 24-hour day using both sundials and mechanical hour indicators.

The canonical hours were introduced to early Christianity from Second Temple Judaism.
By AD 60, the ''Didache'' recommends disciples to pray the Lord's Prayer three times a day; this practice found its way into the canonical hours as well. By the second and third centuries, such Church Fathers as Clement of Alexandria, Origen, and Tertullian