Charles Spurgeon Commentary 1 Kings 12:32

"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 went up unto the altar; so did he in Beth-el, sacrificing unto the calves that he had made: and he placed in Beth-el the priests of the high places that he had made." — 1 Kings 12:32 (ASV)

And Jeroboam ordained a feast in the eighth month, on the fifteenth day of the month, like unto the feast that is in Judah,

He shifted the month, but retained the day—the fifteenth day of the eighth month instead of the seventh. "That was quite unimportant," say some. I do not agree with them, for nothing is unimportant that has to do with the law of God's house.

Disobedience may be more plainly seen in some of the non-essentials than in an essential thing. At all events, we have no right to alter jot or tittle of the divine command.