Good questions.
First though, the "7 times" prophecy is what is directly linked to 1914 based on 2520 years from the fall of Jerusalem. The "day for a year" formula actually forces us to look at double fulfillments; that is, one fulfillment for a literal 24-hour day and one where a day substitutes for a year. Since the NB timeline lasted less than 100 years, it begs a second fulfillment that would extend 2520 years. The interpretation here is that this interval represents the period of time when an earthly representative of God's kingdom would be absent. Thus the fall of Jerusalem is linked with the date of the second coming. I accept this interpretation. But it depends on when you date the fall of Jerusalem. 607/1914 is "absolute chronology", the 2520 years from the fall of Jerusalem to the 2nd coming, though, is "relative chronology."
JWs assign three fulfillments to 1914, but only one applies:
1. The "end of the gentile times" ended on November 30, 1947 when the Jews officially came out of exile. So that's not 1914. Jerusalem was still under gentile rule in 1914. So that is just a misapplication of Luke's reference to the "appointed times of the nations."
2. A "generation" during which all these signs would occur is implied beginning with "nation vs. nation and kingdom vs. kingdom" as the first sign, and thus a world war begins this generation. This would be a generation of 80 years from 1914-1994. To be fulfilled, the 2nd coming would have to occur after the State of Israel is re-born, but before 1994.
3. 607 BCE is not the correct date for the fall of Jerusalem for several reasons:
a) The 70 years per Josephus begin with the time the people are removed off the land, and thus are dated from the last deportation in year 23. So even if you use the pouplar secular date of 537 BCE for the return from Babylon and add 70 years back to 607 BCE, it would mark year 23 of Nebuchadnezzar II and not year 19 or 18. So the "relative chronology" is wrong here.
b) But also, now the "absolute chronology" is wrong. Based on the "70 weeks" proiphecy, this prophecy must begin in the 1st of Cyrus. JWs understand this prophecy begins in 455 BCE based on 29 CE. But they date year 20 of Artaxerxes to 455 BCE rather than the 1st of Cyrus. If the 1st of Cyrus actually occurred in 455 BCE before revisions in the secular timeline, then the 23rd year of Nebuchadnezzar II would fall in 525 BCE and the fall of Jerusalem would be dated to 529 BCE. That means the 2nd coming would fall in 1992 rather than 1914! Our concern here is that 1992 is, indeed, still before the end of a generation that began in 1914 that ends in 1994. So that works out. It is not difficult now to confirm that 455 BCE, indeed, is the Biblical date for the 1st of Cyrus. This is "absolute chronology" applied to the fall of Jerusalem.
c) Finally, the fall of Jerusalem occurs in year 19 of Nebuchadnezzar II and not year 18. The WTS is dating the 18th rather than the 19th year of Neb2 to 607 BCE.
END OF THE GENTILE TIMES: As noted above, the end of the gentile times or the end of the appointed times of the nations occurs on November 30, 1947 when the UN Partition Agreement went into effect, ending Jewish exile. This also ends the "1290 days" mentioned in Daniel 12. "Happy is the one keeping in expectation of the 1335 days!" 1335 days is 45 days more than the 1290 days. Applying a "day for a year" formula, this means the 2nd coming should have occurred 45 years after 1947, and thus in 1992. But we know that when we date the 1st of Cyrus to 455 BCE.
So 607 BCE is incorrect for the fall of Jerusalem, but so is the secular date of 587 BCE. Neither is the fall of Babylon correct for 539 BCE. All these dates are too early because of expansion of the Persian Period. Our best Biblical reference to getting the dates of the NB Period correct is dating the 1st of Cyrus to 455 BCE, then adding 70 years back to the last deportation, year 23. In that case, again, Jerusalem falls in year 19, 529 BCE. That dates the 2nd coming in 1992, the same date you get when you add 45 years to 1947.
So as usual, the WTS, now the "evil slave" and "false prophet" only have part of it correct, but the refined understanding belong to the elect.
WHY IS IT IMPORTANT? The reason why it is important is relative, particularly for JWs since the fall of Jerusalem is linked to the 2nd coming by the "7 times prophecy." But we can date the second coming to 1992 by two other year-specific prophecies. We don't have to unravel all the revised records and complications of ancient history to try to establish the true original date for the reign of Nebuchadnezzar II.
So it is going to be more significant for the elect and, in particular, JWs since they have developed a lot of the Bible chronology prophecies, to get it right. It is a technical correction.
