His chief work is his chronography, in five books. It commenced with the creation (B. C. 5499) and came down to the year 221, the fourth year of Elagabalus. It is the foundation of the mediaeval historiography of the world and the church. We have considerable fragments of it and can restore it in part from the Chronicle of Eusebius. A satisfactory estimate of its merits requires a fuller examination of the Byzantine and oriental chronography of the church than has hitherto been made. Earlier writers were concerned to prove the antiquity of the Christian religion against the heathen charge of novelty by tracing it back to Moses and the prophets who were older than the Greek philosophers and poets. But Africanus made the first attempt at a systematic chronicle of sacred and profane history. He used as a fixed point the accession of Cyrus, which he placed Olymp. 55, 1, and then counting backwards in sacred history, he computed 1237 years between the exodus and the end of the seventy years’ captivity or the first year of Cyrus. He followed the Septuagint chronology, placed the exodus A. M. 3707, and counted 740 years between the exodus and Solomon. He fixed the Lord’s birth in A. M. 5500, and 10 years before our Dionysian era, but he allows only one year’s public ministry and thus puts the crucifixion A. M. 5531. He makes the 31 years of the Saviour’s life the complement of the 969 years of Methuselah. He understood the 70 weeks of Daniel to be 490 lunar years, which are equivalent to 475 Julian years. He treats the darkness at the crucifixion as miraculous, since an eclipse of the sun could not have taken place at the full moon.