1 Kings 12:32-33

New Century Version

³² 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. ³³ So Jeroboam chose his own time for a festival for the Israelites—the fifteenth day of the eighth month. During that time he offered sacrifices on the altar he had built in Bethel. He set up a festival for the Israelites and offered sacrifices on the altar.