1 Kings 12:28, 30, 33

After seeking advice, the king made two golden calves. He said to the people, “It is too much for you to go up to Jerusalem. Here are your gods, Israel, who brought you up out of Egypt.”

And this thing became a sin; the people came to worship the one at Bethel and went as far as Dan to worship the other.

On the fifteenth day of the eighth month, a month of his own choosing, he offered sacrifices on the altar he had built at Bethel. So he instituted the festival for the Israelites and went up to the altar to make offerings.