Archbishop of Armagh and Primate of All Ireland, James Ussher was a serious scholar, well respected in his time. By compiling the periods of time listed in the Bible, he concluded that:
The Earth was created in 4004 BC
The Flood occurred in 2348 BC
The Exodus occurred in 1491 BC
And, curiously, Jesus was born in 5 BC.
He was by no means the only scholar to attempt such a chronology, and others, including Isaac Newton, came to similar conclusions.