
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....