'First Day' in the Bible

They began to offer burnt offerings to the LORD from the first day of the seventh month, even though the foundation of the Temple of the LORD had not yet been laid.

On the first day of the first month he left Babylon and he arrived in Jerusalem on the first day of the fifth month, since the beneficent hand of his God was upon him.

So those who had returned from exile did this. Ezra the priest and leaders of certain ancestral groups listed by name devoted themselves to examine the situation on the first day of the tenth month.

By the first day of the first month they concluded their investigation of all of the men who had married foreign wives.