And Jeroboam ordained a feast on the fifteenth day of the eighth month, like the feast that was in Judah, and he offered sacrifices on the altar; he made this offering in Bethel to sacrifice to the calves he had set up, and he installed priests in Bethel for the high places he had set up.
We have here the beginning of the reign of Jeroboam. He built Shechem first and then Penuel - beautified and fortified them, and probably had a palace in each of them for himself (Kg1 12:25), the former in Ephraim, the latter in Gad, on the other side Jordan.
Commenting on 1 Kings 12:25-33
And Jeroboam ordained a feast in the eighth month, on the fifteenth day of the month, like unto the feast that [is] in Judah, and he offered upon the altar. So did he in Bethel, sacrificing unto the calves that he had made: and he placed in Bethel the priests of the high places which he had made.
Ordained a feast - The Jews held their feast of tabernacles on the fifteenth day of the seventh month; Jeroboam, who would meet the prejudices of the people as far as he could, appointed a similar feast on the fifteenth of the eighth month; thus appearing to hold the thing while he subverted the ordinance.