Manuscripts of two relatively late authors of classical Latin, Aulus Gellius and Nonius Marcellus, have garbled the word duovicesimus, a word that fell out of use after the first century BC. Modern scholars have had difficulty in restoring the true form of the word to the ancient manuscripts and then in assessing the effect of that restoration on the histories written by three authors of the second and first centuries BC, who are cited as having used that word: Fabius Pictor, Cato the Elder, and Varro. Once the valid form of the word is restored and its meaning realized, the following conclusions are possible. Fabius Pictor had his own peculiar chronology of the period between the Gallic sack of Rome and the first plebeian consul. Cato the Elder marked the beginning of the siege of Sarguntum as the sixth violation of a treaty by the Carthaginians. It is highly likely that Varro had Ancus Marcius die in the twenty-second year of his reign.