Exodus 12:2

This month. Sometimes, as here, designated as “the first month of the year” (Ex. 40:2, 17; Lev. 23:5; etc.), also called Abib (Ex. 13:4; 23:15; 34:18; Deut. 16:1). Abib, generally falling in our month of April, means “ear-month,” owing to the fact that grain was then in the ear. After the captivity, Babylonian calendar names were adopted and Abib became Nisan (see Neh. 2:1; Esther 3:7). The new ordinance implies that the Israelite year had hitherto begun at a different time, probably with the month later called Tishri, which corresponds to our September or October. Henceforth two reckonings were employed, one for sacred, the other for civil, purposes, the first month of each year being the seventh month of the other, though the numbers always ran from Nisan as the first.

Abib, “the month of ears,” became now the first month of the ecclesiastical year, and Tishri became its seventh, likewise honored by important feasts later instituted at Sinai.

The civil year, beginning with the month of Tishri, was never abandoned by the Israelites and is still in use among the Jews today. Its existence can be traced through the entire OT period. It was perpetuated by the Jews in the belief that God created the world in the fall of the year.