In previous works I have pointed to Jer. 18:5-8 as an answer to some skeptical charges about God "changing his mind":

Then the word of the Lord came to me, saying... "The instant I speak concerning a nation and concerning a kingdom, to pluck up, to pull down, and to destroy it, if that nation against whom I have spoken turns from its evil, I will relent of the disaster that I thought to bring upon it"

In a 1994 issue of a Skeptical publication, our buddy Skeptic X thinks he can turn this one on its head for us in a specific instance, in which, he says, we find "Yahweh's execution of vengeance on a penitent nation in flagrant violation of his promise to show mercy on nations that turned from their evil ways." Where? The story starts with Manasseh the son of Hezekiah, who did a lot of the usual bad stuff, including some of the nastiest idolatry recorded in the OT (2 Kings 21). God announced serious judgment for this (21:10-15), but Manasseh kept on keeping on (21:16), as did his son Amon (who reigned two years) after he died (21:20). Finally Josiah came on the scene and proceeded to clean things up seriously, doing as much good as Manasseh did bad, if not twice as much.

So what's the issue, toilet tissue? The man on a roll says:

One would think, then, that if any nation were ever entitled to have Yahweh "relent" of the disaster he had pronounced upon it, Judah under the reign of Josiah would certainly have qualified. But it didn't. After all the reforms of Josiah had been described in detail, the writer of 2 Kings made this astonishing announcement:

Nevertheless Yahweh did not turn from the fierceness of His great wrath, with which His anger was aroused against Judah, because of all the provocations with which Manasseh had provoked Him. And Yahweh said, "I will also remove Judah from My sight, as I have removed Israel, and will cast off this city Jerusalem which I have chosen, and the house of which I said, `My name shall be there'" (23:26-27).

"From this," we hear, "one can only conclude that it wasn't always true that when Yahweh spoke 'concerning a nation and concerning a kingdom, to pluck up, to pull down, and to destroy it' that he would 'relent of the disaster' that he had thought to bring upon it if the nation turned from its evil."

One might of course make the point that after Josiah kicked the bucket, his son Jehoahaz, and Jeohaikim after him, made another 180 turn; and the punishment did not at least come during Josiah's reign, but only after these two J-dudes did their worst. Still, X fails the Laubach literacy test yet again. He quotes this part in the original quote above, but somehow misses it the second recital:

At what instant I shall speak concerning a nation, and concerning a kingdom, to pluck up, and to pull down, and to destroy it; If that nation, against whom I have pronounced, turn from their evil, I will repent of the evil that I thought to do unto them. And at what instant I shall speak concerning a nation, and concerning a kingdom, to build and to plant it...

By now we know better than to expect X to consult the Hebrew before blowing off at the horn, but this is really bad to miss the English. The terms of Jeremiah are very specific here: at what instant. Manasseh reigned 55 years, Amon 2 more, for a total of 57 years of rotten behavior. It isn't specified how many years into M's reign the warning of 21:11-15 was made, but even if made in year 54 (unlikely), Josiah's 180 wasn't done "an instant" later as required. Nineveh in Jonah's time was a lot smarter -- they unpacked the sackcloth and shoveled the ashes in less than a day. The word behind "an instant" is rega', and is used to mean "in the wink of an eye" -- sure ain't no 3-55 years. That was pretty simple, wasn't it?