By referring to information in just two of the WTS's publications - Insight on the Scriptures and Babylon the Great has fallen,God's Kingdom Rules (who could ever forget that one!) - and then counting backwards from 539 BC, it becomes evident that the WTS is contradicting itself when it insists on the 607 BC date.
1) That Nabonidus was the last "supreme ruler of the Babylonian Empire" and "ruled for some 17 years" is stated in Volume 2 of Insight on the Scriptures (p.457, under the heading "Nabonidus"). In that particular passage, Insight on the Scriptures even performs the calculation for you!
i.e. It even gives the years of his reign as being from 556 to 559 BC.
2) "Labashi-Marduk ... was a vicious boy, and within nine months had his throat cut by an assassin." (Babylon the Great has fallen, God's Kingdom Rules. p184)
That leaves us still in the year 556 BC.
3)"Neriglassar ... reigned for four years." (Babylon the Great has fallen, God's Kingdom Rules. p184)
So, (when I went to school, at least!), 556 + 4 = 560 BC.
4) "After reigning but two years, King Evil-Merodach was murdered" (Babylon the Great has fallen, God's Kingdom rules. p184).
Adding two years to 560 BC takes us to (560 + 2 )= 562 BC for the beginning of Evil-Merodach's reign.
5) "Nebuchadnezzar ruled as king for 43 years" (Insight on the Scriptures, Volume 2, p.480, under the heading "Nebuchadnezzar").
Adding 43 years to 562 BC (562 + 43) brings us to the year 605 BC as being the start of Nebuchadnezzar's reign.
i.e. two years before the WTS would have us believe that he destroyed Jerusalem and its temple. (Which 2 Kings 25: 2, 8 tells us occurred during the 19th year of his reign - NOTtwo years before it started!. Again, simple maths takes us from 605 - 19 = 586 BC).
It is not for nothing that all informed researchers agree on 586 or 587 BC as being the date of the Jerusalem Temple's destruction - Archeology alone providing overwhelming evidence. However, one only needs to go to the information provided by the Watchtower Society's own publications -and then do some simple mathematics - to see that the 607 BC date is wrong.
Yes, it is contradictory; and yes, it is totally irrational - and those stubbornly clinging to the 607 BC date are well and truly deluding themselves!
Bill.