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Ancient Calendars |
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Before 2000 BCE, the Babylonians (in today's Iraq) used a year of 12 alternating 29 day and 30 day lunar months,giving a 354 day year. In contrast, the Mayans of Central America relied not only on the Sun and Moon, but also the planet Venus, to establish 260 day and 365 day calendars. |
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We have no written records of Stonehenge, built over 4000 years ago in England, but its alignments show its purposes apparently included the determination of seasonal or celestial events, such as lunar eclipses,solstices and so on. |  |
| We know little about
the details of timekeeping in prehistoric eras, but wherever we turn up records and artifacts, we usually discover that in every culture,
some people were preoccupied with measuring and recording the passage of time.Ice-age hunters in Europe over 20,000 years ago scratched lines
and gouged holes in sticks and bones, possibly counting the days between phases of the moon. Five thousand years ago,Sumerians in the Tigris-Euphrates valley in today's Iraq had a calendar that
divided the year into 30 day months, divided the day into 12 periods (each corresponding to 2 of our hours), and divided these periods into 30 parts
(each like 4 of our minutes).
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The earliest Egyptian
calendar was based on the moon's cycles, but later the Egyptians realized
that the "Dog Star" in Canis Major, which we call Sirius, rose next to the sun every 365 days, about when
the annual inundation of the Nile began. Based on this knowledge, they
devised a 365 day calendar that seems to have begun in 4236 BCE
(Before the Common Era), which thus seems to be one of the earliest years
recorded in history. |
This culture and its related
predecessors spread across Central America between 2600 BCE and
1500 CE, reaching their apex between 250 and 900 CE. They left celestial-cycle
records indicating their belief that the creation of the world occurred
in 3114 BCE. Their calendars later became portions
of the great Aztec calendar stones. Our present civilization has adopted
a 365 day solar calendar with a leap year occurring every fourth year
(except century years not evenly divisible by 400). Please note that all text on this page is reprinted with the kind permission of www.physics.nist.gov. |