'First Day' in the Bible

And the LORD spoke to Moses in the wilderness of Sinai, in the tabernacle of the congregation, on the first day of the second month, in the second year after they had come out of the land of Egypt, saying,

And they assembled all the congregation on the first day of the second month, and they declared their pedigrees after their families, by the house of their fathers, according to the number of the names, from twenty years old and upward, by their polls.

And he that offered his offering the first day was Nahshon the son of Amminadab, of the tribe of Judah:

On the first day shall be a holy convocation; in it ye shall do no manner of servile work.

And in the seventh month, on the first day of the month, ye shall have a holy convocation; ye shall do no servile work: it is a day of blowing the trumpets to you.

And Aaron the priest ascended mount Hor at the commandment of the LORD, and died there, in the fortieth year after the children of Israel departed from the land of Egypt, in the first day of the fifth month.