The Babylonian Calendar

Abstract

The Babylonian calendar was a lunar calendar with years consisting of 12 lunar months (about 354 days), each beginning when a new crescent moon was first sighted low on the western horizon at sunset, plus an intercalary month inserted as needed by decree. The calendar is based on a Sumerian (Ur III) predecessor preserved in the Umma calendar of Shulgi (c. 21st century BC).

The year begins in spring, and is divided into reššatti "beginning of the year ", mišilšatti "middle of the year ", and kītšatti "end of the year". The name for "month" was arhu. (During the 6th century BC Babylonian exile of the Hebrews, the Babylonian month names were adopted into the Hebrew calendar. The Aramaic and syriac calendar used till now  in Syria,  Iraq and the Levant also uses many of the same names for its months, such as Ayyar, Tammuz, Ab, Elul, Tishrin, and Adar.