'Fifteenth' in the Bible

You are to hold a festival on the fifteenth day of this month for seven days, during which time unleavened bread is to be eaten."

"You are to hold a sacred assembly on the fifteenth day of the same seventh month. No servile work is to be done. You are to celebrate a festival to the LORD for seven days by

They departed from Rameses in the first month, on the fifteenth day of that first month. The day after the Passover, the Israelis came out confidently, and all the Egyptians watched them leave,