1 Kings 12:32-33

32And Jeroboam ordained a feast in the eighth month, on the fifteenth day of the month, like unto the feast that is in Judah, and he offered upon the altar. So did he in Beth–el, sacrificing unto the calves that he had made: and he placed in Beth–el the priests of the high places which he had made.12

33So he offered upon the altar which he had made in Beth–el the fifteenth day of the eighth month, even in the month which he had devised of his own heart; and ordained a feast unto the children of Israel: and he offered upon the altar, and burnt incense.34