'Fifteenth' in the Bible

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

And on the fifteenth day of the seventh month ye shall have a holy convocation; ye shall do no servile work, and ye shall keep a feast unto Jehovah seven days:

And they journeyed from Rameses in the first month, on the fifteenth day of the first month; on the morrow after the passover the children of Israel went out with a high hand in the sight of all the Egyptians,