We know very little of Quintus Julius Hilarianus. Even his name is uncertain: some hold that he should not be called Hilarianus, but rather Hilarius, and which is rendered Ilarione in Italian (discussion in Lana, p. 80). It is thought that Hilarianus may have been a priest, probably from Africa Proconsularis.

Two of his treatises survive, both chronographies: besides the De cursu temporum (from 397; see the corresponding card), we have the De ratione Paschae et mensis, on his calculations of Easter, whose conclusion and subscription (Migne, PL 13, p. 1114; cfr. Abendstein) seem to establish that he first completed the work at the end of 396, and revised it in 397 (Martindale). It is also hypothesised that he wrote a later chronographical treatise known as the Liber genealogus, composed in Africa in the first quarter of the 5th century (Mommsen, pp. 154-155, Zecchini 1993, Zecchini 2003).  [F. Giannotti; trad. C. Belanger]