From The Art and Popular Culture Encyclopedia
Fasti, a Latin word, refers to the Roman calendar and almanac; and especially, to a long, possibly unfinished poem on the religious festivals of the Roman year and their mythological underpinnings, by the poet Ovid.
In Roman antiquities, fasti is the plural of the Latin adjective fastus, but more commonly used as a substantive, derived from fas, meaning what is binding, or allowable, by divine law, as opposed to jus, or human law. Fasti dies thus came to mean the days on which law business might be transacted without impiety, corresponding to our own lawful days; the opposite of the dies fasti were the dies nefasti, on which, on various religious grounds, the courts could not sit. The word fasti itself then came to be used to denote lists or registers of various kinds, and especially those that had to do with keeping or marking time.