'Fifteenth' in the Bible

On the fifteenth day of this month shall be a feast: seven days shall unleavened bread be eaten.

"'On the fifteenth day of the seventh month you shall have a holy convocation; you shall do no servile work, and you shall keep a feast to Yahweh seven days:

They traveled from Rameses in the first month, on the fifteenth day of the first month; on the next day after the Passover the children of Israel went out with a high hand in the sight of all the Egyptians,