Babylonian calendar facts for kids

Calendar from ancient Nippur, showing how early calendars were structured.

The Babylonian calendar was a special way of keeping track of time used in ancient Mesopotamia. It was a lunisolar calendar, meaning it used both the Moon and the Sun to organize its years and months. This calendar was used for a very long time, from about 2000 BC until around 300 BC, especially in the city of Babylon.

This ancient calendar was very important. It influenced many other calendars that came later, including the Jewish calendar and even parts of our modern Gregorian calendar. For example, the idea of having 12 months in a year and a seven-day week comes from these ancient traditions. The Babylonian calendar also helped shape calendars in places like South and East Asia and the Islamic calendar.

How the Babylonian Calendar Worked

The Babylonian calendar was a lunisolar calendar. This means it tried to follow both the phases of the Moon and the Earth's journey around the Sun. It was based on an older calendar from the Sumerian people, who lived in Mesopotamia even earlier.

Months and the Moon

Each month in the Babylonian calendar began when people first saw the new, thin crescent moon low in the western sky at sunset. This made sure the calendar months always stayed in sync with the Moon's cycle.

Because twelve lunar months are shorter than a full solar year, the Babylonians sometimes added an extra month. This "intercalary month" helped keep the calendar aligned with the seasons, especially for farming. At first, these extra months were added when needed. Later, around 499 BC, they started using a regular pattern, adding extra months in a predictable cycle over 19 years. This cycle is often called the Metonic cycle, named after a Greek astronomer, but the Babylonians used it even before him!

Names of the Months

The names of the months in the Babylonian calendar were very important. Many of these names were later adopted into other calendars, like the Hebrew calendar, the Assyrian calendar, and the Syriac calendar. Even today, some month names in countries like Iraq and Syria are inspired by these ancient Babylonian names.

The first month of the civil calendar was called Nisānu. It usually lined up with the vernal equinox, which is the start of spring in the Northern Hemisphere.

Keeping the Calendar Accurate

The goal of the Babylonian civil calendar was to keep its months aligned with the Moon's phases and its years aligned with the Earth's seasons. Since new months were declared by actually seeing the new crescent moon, the months stayed very close to the Moon's cycle.

To keep the years aligned with the seasons, especially after 499 BC, they used the 19-year cycle to add extra months. This system was quite good at keeping the average length of a year very close to the true length of a solar year. Sometimes, the first day of the year might be a little off from the exact start of spring, but over many years, the calendar stayed accurate.

The Administrative Calendar

Besides the civil calendar, the Babylonians also used another calendar called the administrative or schematic calendar. This calendar was simpler and more predictable. It had 12 months, and each month had exactly 30 days, making a year of 360 days.

This administrative calendar was used for things that needed exact dates and long-term planning. For example, it was used for business deals, keeping track of astronomical observations, and for calculations in mathematics, wages, and taxes.

Babylonian astronomers especially relied on this 360-day calendar for their calculations and predictions about the stars and planets. They would use it to predict when new moons would appear or when the equinoxes (when day and night are equal) and solstices (the longest or shortest days of the year) would happen.

The Seven-Day Week and Special Days

The Babylonians also had a special seven-day cycle. Every seventh day was considered a "holy-day" or a "special day." On these days, people would rest from certain activities and make offerings to different gods and goddesses. For example, the 28th day of the month was known as a "rest-day."

This idea of a regular day of rest or special observance every seven days is very old and influenced many cultures. The Babylonian month, which was about 29 or 30 days long, usually had three seven-day cycles, plus a final week that was a bit longer to complete the month.

Lasting Impact of the Babylonian Calendar

The influence of the Babylonian calendar can still be seen today. The Akkadian names for months, which were used in Babylon, appear in many calendars. In countries like Iraq and the Levant, the names of the months in their Gregorian calendar are based on these ancient names. The Assyrian calendar also uses month names that came from the Akkadian language.

Even in Turkey, while they use the Gregorian calendar, some of their month names were inspired by older calendars that had roots in the Babylonian system. This shows how important and influential the Babylonian calendar was, shaping how people keep time even thousands of years later.

Images for kids

• 

  The MUL.APIN tablet, an ancient guide for understanding the calendar and predicting moon phases.

See also