I must say the whole idea of trying to convert OT Biblical writings into prophecy of absolute dates seems an absolute minefield. So much is dependent on interpretation to correspond with a previous conclusion or belief.
Even the claim that Jeremiah's 7 year period should be interpreted to mean 7 "Luni/Solar years" of 360 days ie 2520 days is problematic but then these days are converted to 2520 Solar years of 365 1/4 days .
Not to mention the various methods used in those days eg Babylon, to add additional days to their Lunar years (354 days) over a 19 yr cycle to synchronize with the Solar years. The Jewish calendar is the same.
How can we know that Jeremiah was using neat 360 day years and not actual Lunar years (354 days) or "adjusted" years to correspond with the Solar 365 1/4 days and if he actually meant 2520 Solar years why didn't he say that.
To hang an exact date of 1914 on such inexact interpretation is difficult to understand.
Also, I would guess that very, very few JW's would know about the chain of assumptions behind specifying that date nor that there is almost unanimous agreement amongst other scholars, secular and religious, that Jerusalem did not fall in 607 BC but 587 BC supported by historical data from multiple sources. The same method used to determine the historical date of the end of the "desolation" which is accepted by the JWs.
