In JW doctrine, and is the result of using 607 B.C as an "anchor date", using the book of Daniel, Chapter 4, as proof.
This is based upon the following, simple reasoning:
7 "times" doesn't mean "7 times". It means "7 years".
But,"7 years" doesn't really mean 7 "years", either. It means "7 years of days".
But, the "days" in "years of days" doesn't really mean "years of days, in which the days actually mean "days", but means "years of days, in which the "days" actually mean "years".
Therefore, it is easy for even a fool to see that "7 times" REALLY means "7 years" but which really means "7 years of days", but which then really means "7 years of days which aren't really days, but years", or simply stated "7 years of days of which days are really years". To put it even so a child can understand it, it means that the "times" aren't "times" at all, but are "years", which aren't "years" at all, but are "years of days", which aren't "days" at all, but are "years" AFTER all, even though they were originally CALLED "times"!
Got all that? There's more.
Strangely, however, for all of this to work, this fulfillment, based upon an ANCIENT text, still requires the use of the ANCIENT calendar for the MODERN fulfillment to work out to 1914. Therefore, ancient text + ancient calendar = modern date in modern calendar.
When doing your calculations, don't forget that there is no "zero year" from B.C to A.D. C.T. Russell forgot that and was quite embarrassed about it. The official WTBS explanation in later, revised, editions of his books was that "the battery was very low in his calculator at that time" and he wasn't aware of it until after the material was printed.
Lastly, the book of Daniel was prophesied to remain "sealed" until the "last days", which, as we know, began in 1914, according to the simple reasoning just presented. So, Russell had to figure out a way to, somehow "unseal" Daniel before it was prophesied that Daniel WOULD be "unsealed" so he could then put forth a prophecy which pointed to exactly when Daniel WAS to be "unsealed", namely at the start of the "last days", in 1914. Russell, therefore, successfully used a "sealed" book to calculate the exact date it was to be "unsealed", which at that time it was officially, "unsealed", but Russell "unsealed" it before that, because he wanted to know beforehand when it WOULD be "unsealed", because only THEN would he know when the "last days" were to start, which was, of course, when Daniel actually WAS to be "unsealed". Got all that?
I apologize to the reader for using so many words, but, this stuff is so, well, "DEEP"!