I found pp 239 here: http://www.strictlygenteel.co.uk/truthfree/truthfree18.html
time measures, and he gave this divine rule for calculating the time: "I. have appointed thee each day for a year." He also was banded until the time measures were up. (Ezekiel 4:6,8) Hence each of the 2,520 days, according to prophetic calculation in Daniel's prophecy, equals one year, solar time. By the same rule the "seven times", or "times of the Gentiles", amount to 2,520 years. In Nebuchadnezzar's time the year began counting from the fall of the year, or about October 1, our time. Since he destroyed Jerusalem in the summer of 606 B.C., that year had its beginning in the fall of 607 B.C. and its ending in the fall of 606 B.C.
Inasmuch as the count of the Gentile "seven times" began its first year at the fall of 607 B.C., it is simple to calculate when they end. From the fall of 607 B.C. to the fall of B.C. 1 is exactly 606 years. From the fall of B.C. 1 to the fall of A.D. 1 is one year, do not forget. Hence from the fall of B.C. 1 to the fall of A.D. 1914 is 1,914 years. Add now 606 years and 1,914 years, and the sum total is 2,520 years, ending in the fall of A.D. 1914. By this method Jehovah, who is an accurate Timekeeper as to his purposes, symbolically foretold that the "times of the Gentiles", that is, the "seven times", would continue and extend to the fall of A.D. 1914. Before that date, therefore, the true Theocratic Government of Messiah, which was foreshadowed by the typical Theocracy at Jerusalem, could not be set up.
This is the research referenced in the re book.