There are 17 ways to get to 587 BCE. See - The Gentile Times reconsidered by Carl Olaf Jansen
An interesting question is whether C T Russell used his own Bible research to get to 1914?
The answer is simple: Not at all. In 1823, John Aquila Brown published the book The Even-Tide. In the second last chapter called: TWO THOUSAND FIVE HUNDRED AND TWENTY YEARS OR DURATION OF THE FOUR TYRANNICAL EMPIRES (page 130) he asserted that the "seven times" of Daniel 4 was a prophetic 2,520 years, running from the beginning of Nebuchadnezzar's reign in 604 B.C. to 1917 A.D.
John Brown believed that Armageddon would then take place. Brown also placed emphasis on the year 1843 (The year which William Miller used). The method Brown used to arrive at his date is exactly the same that Russell adopted, even thinking that Armageddon would arrive in 1914 as did Brown. Russell just adjusted the 604 B.C.E. date to 607.
The idea that Russell got to 1914 using his own research is pure fantasy. It is the product of John Brown who was part of conventional Christianity or what Jehovah's Witnesses like to call: Babylon the Great.
