Note:  Do not rely on this information. It is very old.

Fasti

Fasti, in ancient Rome, strictly the "lawful days" (fas, divine law) on which legal or other business might be done. The succession of these days was long the secret of certain orders of priests, those for the current month only being announced each month by the pontifices. Eventually, however, one Caius Flavius, a scribe of Appius Claudius Ceecus, got hold of the sacred books and published the list. Hence lists of such days were called fasti, and were naturally extended to include anniversaries of notable events, dates of the rising or setting of certain stars, short explanations of some festivals, and other matters such as are contained in a modern almanac. Several inscriptions with such lists have come down to us. Ovid's Fasti, of which only six books exist, are a poetical explanation of the Roman calendar as reformed by Julius Ceesar. These lists were the fasti sacri, while the fasti annates, or historioi, were short lists of the chief magistrates for each year, and of the various notable events in it. Fragments of some of these are also preserved.