Exodus 12:2

This month shall be to you. beginning of months.

The term here employed denotes the new moon, and hence the day of the new moon, or first day of the month, and lastly the month as defined in its commencement by the new moon. It appears to denote here the beginning of the month. The chief of months --the most important among the months on account of the great event which was about to take place in it.-- Murphy. Hitherto the year had commenced with the month Tisri (or September), but henceforth the year was to be reckoned from Abib, the month of Israel's birth. Abib signifies an "ear of grain;" it was the month when barley ripened, corresponding with our close of March and beginning of April. The Hebrew months were lunar, and Abib was the mouth commencing with the new moon just after or just before the vernal equinox. This was the sacred year, by which the festivals were reckoned; but the civil or common year was still reckoned from Tisri.-- F. H. Newhall.