Ancient civilizations were interested and invested in recording and measuring the passage of time. Seasons, months and years were dictated by the motion of the celestial bodies and would lead to the development of the modern day calendar.
Dating back 20,000 years, humans began to understand the importance of recording the passage of time. Ice Age hunters in Europe used sticks and bones to record the days between the phases of the Moon by marking them with scratches and holes. This early civilization took part in extensive traveling and trade, which required the knowledge of astronomy — something that was instrumental in their survival.
The Egyptians in 3100 BCE were the first to officially record one of the earliest years in history. Following a calendar based solely upon the Moon, Egyptians used the seasonal placement of the star Sirius to complete their calendar. Certain difficulties arose when the lunar calendar failed to predict a critical event, the annual flooding of the Nile River. To solve this problem, Egyptians created a civil year based upon the lunar calendar. This calendar was complied of 365 days and divided into three seasons each having four 30-day months.
The Babylonians, in 300 BCE, used a calendar alternating between 29- and 30-day lunar months, which would provide a 354-day year. To help balance the calendar with the solar year, the Babylonians would add an extra month three times every eight years; however, this system did not accurately make up for the differences between the lunar and solar year. Whenever the king felt that the calendar had become too far out of synch with the seasons, he would order an extra month.
Used by the ancient Greeks, their calendar was based on the Moon and is known as the Metonic calendar. Built upon the observations of Meton of Athens in 440 BC, is based on a 19-year cycle which showed that 235 lunar months made up almost exactly 19 solar years.
Modifications were being made to old calendars during the 8th century BCE. The duty of declaring when a new month would begin was placed upon priest-astronomers who declared a new month at the sighting of a new moon. A priest in Rome would observe the sky and relay to the King his sightings of a new moon, and thus, a new month. The number of days between one new lunar crescent to the next would determine a month’s length. Romans referred to this first day in a month as “kalends,” derived from the word “calare,” which means to call out. What we refer to today as calendar came from this custom. Romans, Celts, and Germans all followed this practice of spotting a young crescent moon and declaring the start of a new month.
For more information on the history of ancient calendars, please visit the links listed below:
- National Institute of Standards Technology: Learn the basics of how ancient calendars originated with the Egyptians and Babylonians. You can also read about the development of early clocks.
- Calendars through the Ages: Find out the details on how the first calendar originated and how that impacted and formed the calendar we reference today. Travel through time alongside the ancient civilizations that discovered the need and importance of the calendar.
- The Old Farmer’s Almanac: Astronomy was pivotal in establishing the lunar calendar. Check out this site to learn about Moon phases and lunar eclipses.
- Eric Weisstein’s World of Astronomy: Discover not only how ancient civilizations came to define a calendar, but learn the details of how the calendar was refined throughout the 19th century.
- Calendar through the Ages: Early Roman Calendar: Get the specifics on what the Romans considered to be a calendar, what it looked like, and the functions that the ancient calendar served.