Xander said,
: So, where did the WTBTS explanation of 607 as the date go wrong? What data did they use to come up with that date (and how was it wrong), or, perhaps, what data did they misuse (and the error in their method) to come up with that date?
It was actually Nelson Barbour who came up with the wrong chronology in 1875. After Russell met up with him in 1876, he just accepted Barbour's wrong ideas lock, stock and barrel. Barbour went wrong in two critical areas: (1) He used a wrong date (536 B.C.) as the date of Babylon's destruction and the year of the Jews' return to Judah; (2) More critically, he used a wrong interpretation of "the 70 years of Jeremiah" (Jer. 25:11, 12; 29:10) published by an English clergyman, one Christopher Bowen, around 1860, to claim that the Jews were in captivity in Babylon from 606 to 536 B.C. (in 1943 and 1944 the WTS changed these dates to 607 and 537).
For a full discussion of this stuff, see Carl Jonsson's The Gentile Times Reconsidered (available at various places, including www.freeminds.org and www.amazon.com).
In a nutshell, Barbour and Russell interpreted the references in Jeremiah to "70 years" as years of captivity of the Jews in Babylon and as a time period when Judah was completely empty of inhabitants. This was wrong, since they neglected a good deal of biblical as well as secular evidence. For example, Jeremiah 25:11, 12 indicate that many nations, including the Jews, would serve the king of Babylon for 70 years, and that after 70 years had passed the king of Babylon would be punished. 2 Chronicles 36:20 states directly that after the Persians came to power (which occurred in 539 B.C.) the Jews were no longer captive to the king of Babylon. Thus, the apparent prophecy given by Jeremiah ended in 539 B.C. But the WTS claims that the Jews remained captive to the king of Babylon until 537 B.C. when Cyrus, king of Persia, allowed them to return home. Therefore, if the 70 years is assumed to be an exact period, then it must have begun around 609 B.C. So we see that WTS interpretations have always been wrong, and they have never had a solid basis for their 1914 doctrine.
You can find a detailed discussion of how the WTS changed its date system in 1943 and 1944 here http://www.geocities.com/osarsif/index2.htm in the articles 'The Evolution of 606 to 607 B.C.E. in Watchtower Chronology', 'The Change of 606 to 607 B.C. as the Start of the "Gentile Times"' and 'History of the Change of 606 to 607 B.C. in Watchtower Chronology'.
AlanF