What is the date of creation?
Robert Sungenis holds that there is one correct date of creation, a little earlier than Ussher's 4004 BC. The difference is Israel's stay in Egypt: Ussher counted 215 years, while Sungenis insists on the full 430 years that Exodus 12:40 states.
I wonder if you have come across the papers by Griffith and White discussing their Chronological Framework of Ancient History (CFAH), particularly this one where they triangulate dates for the Creation and the Flood. It would seem to provide a strong argument for 4004 BC as the date of creation. I gather that isn't your favorite date, but it is the date Bossuet used in his Discourse on Universal History. Does this question even matter? Or is it fair to say that if God wanted us to have a definite way to calculate the date of creation that he would have given us one?
Answer
Ussher's date is close, but every chronologer has to make choices when he sets his date, and there are about four of them. One choice he has to make is whether Israel was in Egypt for 215 years or the full 430 years. Ussher chose 215, which is why his date of 4004 BC is less than the one I have. I am adamant that the stay in Egypt was 430 to the very day, since Exodus 12:40 says so, emphatically. And yes, there is a correct date God wants us to have, just like there is only one Scripture that God wants us to have even though there are a lot of Greek and Hebrew manuscripts with slightly different texts.