1 Kings 12:32-33

32Jeroboam made a festival in the eighth month on the fifteenth day of the month, like the festival in Judah. He offered sacrifices on the altar; he made this offering in Bethel to sacrifice to the calves he had made. He also stationed the priests in Bethel for the high places he had made.

33He offered sacrifices on the altar he had set up in Bethel on the fifteenth day of the eighth month. He chose this month on his own. He made a festival for the Israelites, offered sacrifices on the altar, and burned incense.