1 Kings 12:28, 30, 33

King Jeroboam asked for advice. Then he made two golden calves. “It is too long a journey for you to go to Jerusalem to worship,” he said to the people. “Israel, here are your gods who brought you out of Egypt.”

This became a very great sin, because the people traveled as far as Dan to worship the calf there.

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.