Sextus Julius Africanus' Chronographai - a history of the world in five volumes - set the date of creation at 5500 BCE. Later apocalypticists would work forward from this date in calculating the end of the world. (A common assumption among early Christian eschatologists was of the "hexameron" - a 6000-year plan of universal history, reflecting the week of creation described in Genesis. The seventh millennium would mark the Parousia, or Christ's second coming to earth.)
Sextus Julius Africanus died during the year 240.
