The Fasti (traditionally known in English as the "Book of Days") is a six-book Latin poem written by the Roman poet Ovid and published in 8 AD. Ovid is believed to have left the Fasti incomplete when he was exiled to Tomis by the emperor Augustus in 8 AD. Written in elegiac couplets and drawing on conventions of Greek and Latin didactic poetry, the Fasti is structured as a series of eye-witness reports and interviews by the first-person vates ("poet-prophet" or "bard") with Roman deities, who explain the origins of Roman holidays and associated customs—often with multiple aetiologies. The poem is a significant, and in some cases unique, source of fact in studies of religion in ancient Rome; and the influential anthropologist and ritualist J.G. Frazer translated and annotated the work for the Loeb Classical Library series. Each book covers one month, January through June, of the Roman calendar, and was written several years after Julius Caesar replaced the old system of Roman time-keeping with what would come to be known as the Julian calendar.
The popularity and reputation of the Fasti has fluctuated more than that of any of Ovid's other works. The poem was widely read in the 15th–18th centuries, and influenced a number of mythological paintings in the tradition of Western art. However, as one scholar has observed, throughout the 20th century "anthropologists and students of Roman religion … found it full of errors, an inadequate and unreliable source for Roman cultic practice and belief. Literary critics have generally regarded the Fasti as an artistic failure." Subsequently, from the late 1980s, the work has enjoyed a revival of scholarly interest, and has been published in several new English translations. Ovid was exiled from Rome for his subversive treatment of Augustus, yet the Fasti continues this treatment—which has led to the emergence of an argument in academia for treating the Fasti as a politically weighted work.