1 Kings 12:29, 32

Jeroboam put one golden calf in the city of Bethel and the other in the city of Dan.

And he started a new festival on the fifteenth day of the eighth month, just like the festival in Judah. During that time the king offered sacrifices on the altar, along with sacrifices to the calves in Bethel he had made. He also chose priests in Bethel to serve at the places of worship he had made.