Ancient Calendars

Time Keepers

Celestial bodies - the sun, moon, planets, and stars - have provided us a reference for measuring the passage of time throughout human existence. Ancient civilizations like: China, India, Babylon, and Greece relied upon the apparent motion of these bodies through the sky to record and determine seasons, months, and years. We know little about the details of timekeeping in prehistoric eras. However, records and artifacts usually uncover that in every culture, people were preoccupied with measuring and recording the passage of time. Stonehenge, built over 4000 years ago in England has no written records, but its alignments show its purposes apparently included the determination of seasonal or celestial events, such as lunar eclipses, solstices and so on. As time has passed so has the evolution of the calendar, a device created to track our time and seasons from the earliest recordings in Babylonia to the Gregorian calendar the history of this transformation is and interesting journey.

The earliest know calendar to keep track of the cycles of the celestial bodies was an Egyptian calendar that was based on the moon's cycles and is thought to have been created in 4236 B.C.E. Many cultures and societies have embraced the idea of tracking time and seasons as they pass for a myriad of reasons, “Seafarers needed to navigate their vessels, and farmers had to know when to plant their crops.” (Chaisson / McMillan p.30) The Chinese are credited with having invented the second oldest method of time keeping; Emperor Huangdi implemented the Chinese legend in 2637 B.C.E.

Babylonia (where modern day Iraq can be found) is attributed with having some of the earliest surviving records of astronomical observations. It is believed, ‘…Babylonian astronomical knowledge spread far and wide – to the East, to Persia, and to the Mediterranean.” (Richards p. 38) However, the knowledge that was disbursed was not treasured by all that received it, in the Mediterranean the Greeks improved upon the theories of the Babylonians. The Greek’s theories were recorded; however, when Rome over-took most of Europe the records fell into the hands of the Christian church. When Constantine was Emperor of Rome he declared Christianity to be the official religion of the empire; thus, giving the church officials the power to decide the validity of the recordin...

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...ius (1537-1612), he signed a papal bull and that was followed by, “The actual change over to the new calendar took place the following year on 4 October. After 350 years or more the reform had at last been accomplished.” (Richards p.246) Furthermore the rule for leap years (which said that years divisible with 4 should be leap years) was changed so that years, at the end of the century, should be leap years only if they were divisible with 400 (e.g. 1600, 2000, 2400 etc.)

In the Gregorian Calendar there is then 303 years with 365 days and 97 years with 366 days, which gives a mean year of 365.24250 days: 365 days, 5 hours, 49 minutes and 12 seconds. Related to the mean interval between vernal equinoxes this corresponds to a slippage of less than one hour in every 300 years for the foreseeable future - until circa 4000 AD.

Chaisson, Eric and Steve McMillan. Astronomy Today. New Jersey: Prentice

Hall, 1999.

Evenson, A.E. About the History of the Calendar. Canada: Regensteiner

Publishing, 1972.

Richards, E. G. Mapping Time, The Calendar and its History. New York: Oxford

University Press, 1998.