Where did calendars begin?

Early in history man began counting time by days, months and seasons and so had the beginnings of a calendar. When he studied the supposed movement of the sun more closely he began to use the year as a unit of time.

The Greeks dated everything from the Olympic Register, a traditional list of the victors in the Olympic games starting in 776 B.C. The Romans counted time from the founding of their city in 753 B.C. The Mohammedans use the Hejira, or flight of Mohammed from Mecca, A.D. 622. Jewish reckoning dates back to the Creation, calculated as having taken place 3,760 years and three months before Christ’s birth-date. The Christian practice of dating events from the birth of Christ did not come into general use until the time of Charlemagne (9^th Century), and a mistake was made which placed the Christ’s birth five years too late.

In 46 B.C. , acting on the advice of the astronomer Sosigenes, Julius Caesar fixed the year at 356 ¼ days, giving every fourth year, or leap year, an extra day. But the correction by a whole day every four years was too much, and by the 16^th Century the Julian calendar was 13 days behind the solar year.

In 1582, Pope Gregory XIII directed that 10 days should be dropped from the calendar. He also directed that three times in every 400 years the leap year arrangement should be omitted, by not counting as leap years the years ending in two noughts unless they are divisible by 400. This arrangement will keep the calendar and the solar year together until the year 5,000, when the difference will be one day.