here's some interesting quotes from this website: http://members.aol.com/beyondjw/itow.htm
Note one is a magazine just after Oct. 1914.
"Studying God's Word, we have measured the 2520 years, the seven symbolic times, from that year 606 B.C. and have found that it reached down to October, 1914, as nearly as we were able to reckon. We did not say positively that this would be the year." (Watchtower, November 1, 1914, p. 325)
Does that sound like they were impressed with their "hit"? Or just trying to ride through whatever came their way?
This next quote shows how they were trying to keep a bit of a range or time buffer for their prophetic speculations, but would have to concede it was all wrong if things didn't go as they said.
".... Suppose that A.D. 1915 should pass with the world's affairs all serene and with evidence that the "very elect" had not all been "changed" and without the restoration of natural Israel to favor under the New Covenant (Rom. 11:12,15). What then? Would not that prove our chronology wrong? Yes, surely! Would not that prove a keen disappointment? Indeed it would! It would work irreparable wreck to the parallel dispensations and Israel's double, and to the Jubilee calculations, and to the prophecy of the 2300 days of Daniel, and to the epoch called "Gentile Times," and to the 1,260, 1,290, and 1,335 days.... none of these would be available longer." (w1907, 10/1, p 295)