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Tuesday, December 2, 2014

Lunar Calender (c. 15,000 B.C.E.)

Early humans record the passing of time.

The earliest known lunar calendar is in the caves at Lascaux, southwest France, and dates from around 15,000 B.C.E. Various series of spots represent half of the moon's near-monthly cycle, followed by a large empty square, which perhaps indicate a clear sky.

A lunar calendar counts months (a period of 29.5350588 days) and is based on the phases of the moon. Months ahve twenty-nine  and thirty days alternately, and additional days are added ever now and then to keep step with the actual moon phase.

The lunar calendar was widely used in parts of the ancient world for religious observations. Agriculturally the lunar calendar is confusing as it takes no account of annual seasonal variations in temperature, daylight length, plant growth, animal migration, and mating. The lunar month divides into the solar year twelve times but with 10.88 days remaining.

Meton of Athens (circa 440 B.C.E.) noticed that nineteen solar years were equal to 234.997 lunar months. This led to the nineteen-year Metonic cycle where years three, five, eight, eleven, thirteen, sixteen, and nineteen had thirteen lunar months each, and all the other years had twelve months.