calendar

calendar [Lat., from Kalends], system of reckoning time for the practical purpose of recording past events and calculating dates for future plans. The calendar is based on noting ordinary and easily observable natural events, the cycle of the sun through the seasons with equinox and solstice, and the recurrent phases of the moon.

Sections in this article:

• Introduction
• Reckoning the Dates Assigned to Years
• Other Calendars
• The Islamic Calendar
• The Jewish Calendar
• The Christian Ecclesiastical Calendar
• The Gregorian Calendar
• The Julian Calendar
• The Early Roman Calendar
• Measures of Time
• Bibliography

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2025, Columbia University Press. All rights reserved.

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