For those who may not be aware, the 1914 date was arrived at by Russell by using the same framework of the failed prophetic interpretations of the Adventist preacher William Miller.
See this chart:
If you look at the top right of the chart, he uses the same 7-times reasoning to arrive at the 2,520 years (7 times=7 multiplied by 360-day years=2,520 years). Except he begins counting the beginning of the gentile times in 677 B.C. when Israel was supposedly carried captive. Since he began counting in 677 B.C. and not 607 B.C. as Russell did, Miller arrived at 1843, not 1914.
It's noteworthy that Miller and Russell made the same mistake: not realizing there was no 0 year. Miller fixed this by moving the end date from 1843 to 1844. Russell did the opposite. He moved the start date from 606 B.C. to 607 B.C.
Seeing as how this is the same reasoning, does anyone know why Miller chose 677 B.C. as the start date? Obviously, it was because it would have come during his lifetime and people seem to have a built in bias to believe their era is a particularly meaningful one, but what might have been his scriptural reasoning?
Link to full-size chart: http://www.bible.ca/pre-miller-1843-ellen-white.gif