'First Day' in the Bible

"'Seven days you shall eat unleavened bread; even the first day you shall put away yeast out of your houses, for whoever eats leavened bread from the first day until the seventh day, that soul shall be cut off from Israel.

In the first day there shall be to you a holy convocation, and in the seventh day a holy convocation; no manner of work shall be done in them, except that which every man must eat, that only may be done by you.

In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, until the twenty first day of the month at evening.

"On the first day of the first month you shall raise up the tabernacle of the Tent of Meeting.

It happened in the first month in the second year, on the first day of the month, that the tabernacle was raised up.