I am reading again the work.."The Gentile Times Reconsidered" by Carl Olof Jonsson.
It is very heavy going but he uses world sources as used by wt to totally refute the 607 thing. He sent his studies on this to Bethel NY and waited on jehovah. The wts does not like any sort of challenge and he was dfd.
Dozens of rabbis and other theologians all used the "Day for a year" thing and all came to naught from as far back as eleven hundred and something.