'First Day' in the Bible

From the first day of the seventh month they began to offer burnt offerings to the Lord, but the foundation of the temple of the Lord had not been laid.

But the exiles did so. And Ezra the priest selected men who were heads of fathers’ households for each of their father’s households, all of them by name. So they convened on the first day of the tenth month to investigate the matter.

They finished investigating all the men who had married foreign wives by the first day of the first month.