'Fifteenth' in the Bible

And Jeroboam gave orders for a feast in the eighth month, on the fifteenth day of the month, like the feast which is kept in Judah, and he went up to the altar. And in the same way, in Beth-el, he gave offerings to the oxen which he had made, placing in Beth-el the priests of the high places he had made.

He went up to the altar he had made in Beth-el on the fifteenth day of the eighth month, the month fixed by him at his pleasure; and he gave orders for a feast for the people of Israel, and went up to the altar, and there he made the smoke of his offerings go up.