The Island of the Day Before.

The Island of the Day Before (Italian: L'isola del giorno prima) is a 1994 historical fiction novel by Umberto Eco set in the 17th century during the historical search for the secret of longitude. The central character is Roberto della Griva, an Italian nobleman stranded on a deserted ship in the Pacific Ocean, and his slowly decaying mental state, in a backdrop of Baroque-era science, metaphysics, and cosmology.