Exodus 12:2 - Ellicott's Commentary On The Whole Bible

The beginning of months. — Hitherto the Hebrews had commenced the year with Tisri, at or near the autumnal equinox. (See Exodus 23:16.) In thus doing, they followed neither the Egyptian nor the Babylonian custom. The Egyptians began the year in June, with the first rise of the Nile; the Babylonians in Nisannu, at the vernal equinox. It was this month which was now made, by God’s command, the first month of the Hebrew year; but as yet it had not the name Nisan: it was called Abib (Exodus 13:4), the month of “greenness.” Henceforth the Hebrews had two years, a civil and a sacred one (Joseph., Ant. Jud., i. 3, § 3). The civil year began with Tisri, in the autumn, at the close of the harvest; the sacred year began with Abib (called afterwards Nisan), six months earlier. It followed that the first civil was the seventh sacred month, and vice versa.