'First Day' in the Bible

From the first day of the seventh month they began to offer burnt offerings to Yahweh. But the temple of Yahweh was not yet founded.

For on the first day of the first month he began the journey from Babylonia; and on the first day of the fifth month he came to Jerusalem, for the good hand of his God [was] on him.

The {returned exiles} did so. Ezra the priest selected men, the heads of the {families} according to the house of their fathers, all of them by name. They sat down to examine the matter on the first day of the tenth month.

They finished [investigating] all the men who married foreign women by the first day of the first month.