I quite agree with never a jw.. there are no dates in the bible at all that can be fixed on. It is all pure conjecture. The only way any dates can be assumed is based on secular evidence, whether it's for 587BCE or 539BCE or any other date. Anyone reading the bible and the events in there have to make IT fit with secular evidence and not the other way around.
Where in the bible does it give an exact date for the fall of Jerusalem? It doesn't. Where in the bible does it gve an exact date for the fall of Babylon? It doesn't.