1Kgs 12:32-33

32Jeroboam appointed a festival on the fifteenth day of the eighth month like the festival that was in Judah, and he offered sacrifices on the altar; so he did in Bethel, sacrificing to the calves that he had made. And he placed in Bethel the priests of the high places that he had made.33He went up to the altar that he had made in Bethel on the fifteenth day in the eighth month, in the month that he alone had devised; he appointed a festival for the people of Israel, and he went up to the altar to offer incense.