1 Kings 12:32-33

Jeroboam held a feast on the fifteenth day of the eighth month, like the feast which is kept in Judah, and he went up to the altar; he did this in Bethel, sacrificing to the calves which he had made. And he stationed in Bethel the priests of the high places which he had made. [Lev 23:34] So he went up to the altar which he had made in Bethel on the fifteenth day of the eighth month, in the month which he had devised in his own heart [in defiance of God’s commandments]; and he held a feast for the Israelites and he went up to the altar to burn incense [in defiance of God’s law.]