I did mean to add that in his book, Even-Tide, John Aquila Brown says (pp.132, 135)
in the year 606, that the destruction or first captivity of the Jewish nation
took place, and in 604 A.C. that Nebuchadnezzar ascended the throne of Babylon, on the demise of his father or grandfather.
therefore, the calculation of the “seven times,” from the first year of
Nebuchadnezzar, A.C. 604, whose kingdom is the golden head of the image, and is
represented by the towering and palmy “tree,” previously to its desolation, the
termination of these 2520 years will fall out in the year 1917.
So, although he apparently came up with the idea of 2520 years he counted it from 604 when Nebuchadnezzar ascended the throne, not from the time he destroyed Jerusalem.eighteen years later.