Londo, don't you wish you never had to research that in the first place? But since WT insists there's a SECOND FULFULLMENT to a prophecy that was clearly already fulfilled with Nebuchadnezzar, they have created a made-up prophecy!!!!! 607/586 is just a way to get us all driveling on about a date. I'd venture to say that none of us would care if the "Seven Times" / "2,520 years" prophecy didn't exist in the first place, which, when any sane person reading the Bible would see, does not!
The Daniel's Prophecy book, pgs 95-96, par. 26 states: "Evidently, Nebuchadnezzar’s “seven times” involved seven years. In prophecy, a year averages 360 days, or 12 months of 30 days each. (Compare Revelation 12:6, 14.) So the king’s “seven times,” or seven years, were 360 days multiplied by 7, or 2,520 days. But what about the major fulfillment of his dream? The prophetic “seven times” lasted much longer than 2,520 days. This was indicated by Jesus’ words: “Jerusalem will be trampled on by the nations, until the appointed times of the nations are fulfilled.” (Luke 21:24) That ‘trampling’ began in 607 B.C.E. when Jerusalem was destroyed and the typical kingdom of God ceased to function in Judah. When would the trampling end? At “the times of restoration of all things,” when divine sovereignty would again be manifested toward the earth through symbolic Jerusalem, the Kingdom of God.—Acts 3:21."
I can agree with the first sentence, but then they make this strange leap to a whole other prophecy that just is not alluded to at all in the Bible. The explanation doesn't even make sense. The prophecy is about a Babylonian king going mad, but then regains his mental state and has his kingdom restored, but somehow, WT makes this prophecy about Jerusalem being trampled on by the nations. Huh? This is a clear and classic example of cherry-picking completely unrelated verses to meet some odd belief system.
I mean really... why not apply that "day for a year" rule with everything?
Let me give it a go... (what follows is pure sattire)
Jesus was raised up after three days, so that must represent three years! What happened three years later? Well, the first of the Gentiles came in in 36C.E. (Now I get it. Jesus death is related to the death of the Jewish nation and the birth of the Gentiles! <face palm>)
Jesus reign is for a thousand years. Let's see, day for a year (using 360 days, of course) would mean 360 * 1000 = 360,000 years. Wow! Now there's new understanding for how long Jesus reign REALLY is. (it's all so clear now!)
The flood of Noah's day had them in the Ark for 40 days. 40 days = 40 years. Day for a year is 360 * 40 = 14,400 years! Holy cow, the flood hasn't ended yet! It's still going on (invisibly, of course)!
Seriously...