FASTI, in Roman antiquities, 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, which may be divided into two great classes.
1. Fasti Diurni, divided into urbani and rustici, a kind of official year-book, with dates and directions for religious ceremonies, court-days, market-days, divisions of the month and the like. Until 304 B.C. the lore of the calendaria remained the exclusive and lucrative monopoly of the priesthood; but in that year Gnaeus Flavius, a pontifical secretary, introduced the custom of publishing in the forum tables containing the requisite information, besides brief references to victories, triumphs, prodigies, etc. This list was the origin of the public Roman calendar, in which the days were divided into weeks of eight days each, and indicated by the letters A-H. Each day was marked by a certain letter to show its nature; thus the letters F., N., N.P., F.P., Q. Rex C.F., C., EN., stood for fastus, nefastus, nefastus in some unexplained sense, fastus priore, quando rex (sacrorum) comitiavit fastus, comitialis and intercisus. The dies intercisi were partly fasti and partly nefasti. Ovid's Fasti is a poetical description of the Roman festivals of the first six months, written to illustrate the Fasti published by Julius Caesar after he remodelled the Roman year. Upon the cultivators fewer feasts, sacrifices, ceremonies and holidays were enjoined than on the inhabitants of cities; and the rustic fasti contained little more than the ceremonies of the calends, nones and ides, the fairs, signs of zodiac, increase and decrease of the days, the tutelary gods of each month and certain directions for rustic labours to be performed each month
2. Fasti Magistrales, Annales or Historici, were concerned with the several feasts, and everything relating to the gods, religion and the magistrates; to the emperors, their birthdays, offices, days consecrated to them, with feasts and ceremonies established in their honour or for their prosperity. They came to be denominated magni, by way of distinction from the bare calendar, or fasti diurni. Of this class, the fasti consulares, for example, were a chronicle or register of time, in which the several years were denoted by the respective consuls, with the principal events which happened during their consulates. The fasti triumphales and sacerdotales contained a list in chronological order of persons who had obtained a triumph, together with the name of the conquered people, and of the priests. The word fasti thus came to be used in the general sense of "annals" or "historical records." A famous specimen of the same class are the fasti Capitolini, so called because they were deposited in the Capitol by Alexander Farnese, after their excavation from the Roman forum in 1547. They are chiefly a nominal list of statesmen, victories, triumphs, etc., from the expulsion of the kings to the death of Augustus. A considerable number of fasti of the first class have also been discovered; but none of them appear to be older than the time of Augustus. The Praenestine calendar, discovered in 1770, arranged by the famous grammarian Verrius Flaccus, contains the months of January, March, April and December, and a portion of February. The tablets give an account of festivals, as also of the triumphs of Augustus and Tiberius. There are still two complete calendars in existence, an official list by Furius Dionysius Philocalus (A.D. 354), and a Christian version of the official calendar, made by Polemius Silvius (A.D. 448). But some kinds of fasti included under the second general head were, from the very beginning, written for publication. The Annales Pontificum - different from the calendaria properly so called - were "annually exhibited in public on a white table, on which the memorable events of the year, with special mention of the prodigies, were set down in the briefest possible manner." Any one was allowed to copy them. Like the pontifices, the augurs also had their books, libri augurales. In fact, all the state offices had their fasti corresponding in character to the consular fasti named above.
For the best text and account of the fragments of the Fasti see Corpus Inscriptionum Latinarum, i. (2nd ed.); on the subject generally, Teuffel-Schwabe, Hist. of Roman Literature, §§ 74, 75, and article by Bouché-Leclercq in Daremberg and Saglio, Dictionnaire des antiquités.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)