Quintus Julius Hilarianus (fl. 397), commonly known as Hilarian, was a Roman African chronographer and computist. He is sometimes identified with the bishop Hilarianus who attended the Council of Carthage in 411. This is uncertain and he may have even been a Donatist. His writings point to his having been a monk.[1]
Hilarianus is known for two works in Latin:
- De ratione Paschae et mensis (or Expositum de die Paschae et mensis) was completed on 5 March 397.[1] It is a treatise about the importance of celebrating Easter.[2] It has been read as a sermon,[2] but this is not certain.[1] It is used in the Carthaginian Computus of 455, which also cites a letter of one Agriustias to Hilarianus on the subject of computus.[1]
- Written later in 397, the Chronologia siue Libellus de mundi duratione (or De cursu temporum) is a treatise on salvation history.[1][2] It argues that the Second Coming will occur in 498, when the Earth is 6,000 years old. There will follow the thousand-year reign of Christ and a final battle. Since the end of the world is placed beyond the lifetime of Hilarianus or his initial audience, the Libellus does not seem to be a response to contemporary events but "a statement about hope for life eternal". Its brand of millenarianism, however, soon came to be regarded as heresy, making Hilarianus "one of [its] last vocal proponents".[2] Nevertheless, in two groups of manuscripts the Libellus was incoporated into the compilation known as the Chronicle of Fredegar. In one group, it replaces the contribution of the Liber generationis.[3] The 9th-century manuscript Reginensis 213 opens with it.[4][5]
Some scholars have suggested Hilarianus as the author of the Liber genealogus.[6]