Babylonian Calendar - Months

Months

The year begins in spring, and is divided into reš šatti "beginning", mišil šatti "middle", and kīt šatti "end of the year". The name for "month" was arḫu (status constructus araḫ). That the calendar originates in Babylonian, not Assyrian times is shown by the fact that the chief deity of the Assyrians is assigned the surplus intercalary month. During the 6th century BC Babylonian exile of the Hebrews, the Babylonian month names were adopted into the Hebrew calendar. The Aramaic calendar used in Iraq and the Levant also uses many of the same names for its months, such as Iyyar, Tammuz, Ab, Elul, Tishri, and Adar.

Until the 5th century BC the calendar was fully observational, but beginning about 499 BC the months began to be regulated by a lunisolar cycle of 19 years equaling 235 months. Although usually called the Metonic cycle, Meton (432 BC) probably learned of the cycle from the Babylonians. After no more than three isolated exceptions, by 380 BC the months of the calendar were regulated by the cycle without exception. In the cycle of 19 years, the month Adaru 2 was intercalated, except in the year that was number 17 in the cycle, when the month Ululu 2 was inserted. During this period, the first day of each month (beginning at sunset) continued to be the day when a new crescent moon was first sighted—the calendar never used a specified number of days in any month.