Chronography of 354 (Calendar of Filocalus)

The Chronography of 354 is a Roman illuminated manuscript compiled by the calligrapher Furius Dionysius Filocalus, combining a civil calendar, a list of consuls, and other reference material including one of the earliest surviving references to the Christian feast of Christmas being celebrated on December 25. As a primary source it is directly dated evidence from the year it names, making it unusually valuable for questions about fourth century Roman civil and religious calendar practice. Its limit is that it survives only through later medieval copies rather than the original fourth century manuscript, so questions about the exact original illustrations or wording of any specific entry depend on how faithfully those copies preserved the lost original, a genuine source critical caveat scholars account for.