'First Day' in the Bible

Now the Lord spoke to Moses in the tent of meeting in the wilderness of Sinai on the first day of the second month of the second year after the Israelites departed from the land of Egypt. He said:

and they assembled the entire community together on the first day of the second month. Then the people recorded their ancestry by their clans and families, and the men who were twenty years old or older were listed by name individually,

The one who presented his offering on the first day was Nahshon son of Amminadab, from the tribe of Judah.

"'On the first day of each month you must offer as a burnt offering to the Lord two young bulls, one ram, and seven unblemished lambs a year old,

And on the first day there is to be a holy assembly; you must do no ordinary work on it.

"'On the first day of the seventh month, you are to hold a holy assembly. You must not do your ordinary work, for it is a day of blowing trumpets for you.

Aaron the priest ascended Mount Hor at the command of the Lord, and he died there in the fortieth year after the Israelites had come out of the land of Egypt on the first day of the fifth month.