Overview

Keeping track of the passage of time has been a human preoccupation since the dawn of history. Calendars helped societies to understand and track the changing seasons and to mark the elapse of time between important human events such as religious holidays. But producing accurate calendars was an enormous challenge, and proved to be a great stimulus for the advance of astronomy and mathematics from ancient Mesopotamia through Renaissance Europe.

Background

Some of the very earliest evidence of recorded history reveals the importance to all civilizations of calendars. Traces of calendars from prehistoric civilizations have been found at Stonehenge as well as at sites in the Americas, but among the earliest calendars about which historians have significant and detailed evidence are those of the Egyptians and Babylonians. The Egyptian calendar relied on practical principles rather than elaborate astronomical investigations; that is, it was...