John Gill Commentary Exodus 13:4

"This day ye go forth in the month Abib." — Exodus 13:4 (ASV)

This day came you out
Out of Egypt, on the fifteenth of Nisan, as the Targum of Jonathan: in the month Abib ;
which signifies an ear of corn, because in this month barley was in the ear, see (Exodus 9:31) , the Syriac version renders it, "in the month of flowers"; when the flowers were rising up out of the earth, being spring time, and a very fit time to travel in;

and this is observed, not only because they might not know what month it was, in such a state of ignorance, as well as servitude, were they kept in Egypt; but as Jarchi also intimates, to point out to them the mercy and goodness of God to them, in bringing them out at such a seasonable time to travel in, when there were neither heat, nor cold, nor rain. This month answers to part of our March, and part of April.