James Ussher was Chancellor of this St Patrick's Cathedral in 1605. But that's not why he is so famous. He calculated the date of the Creation. He defined it as the nightfall on 22 October 4004 BC. It is pubslihed in his most famous work, the Annales veteris testamenti, a prima mundi origine deducti ("Annals of the Old Testament, deduced from the first origins of the world"), which appeared in 1650, and its continuation, Annalium pars posterior, published in 1654.