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From Anglo-Norman and French ides, from Latin īdūs, a fourth-declension pluralia tantum, from the Latin practice of treating most recurring calendrical days as plurals. The Latin term is cognate with Oscan eiduis, both perhaps deriving from an unknown Etruscan term. Middle English and Old French also used the singular form ide.
ides (plural ides)
- (historical, often capitalized) The notional full-moon day of a Roman month, occurring on the 15th day of the four original 31-day months (March, May, Quintilis or July, and October) and on the 13th day of all other months.
- 10th century, Byrhtferð of Ramsey, Enchiridion (Ashmolean MS 328), Book I, Chapter ii, Section 22:
- 1679, J. Moxon, Mathematics made Easie, p. 26:
- 1967, Agnes Kirsopp Michels, Calendar of the Roman Republic, p. 22:
- For the modern reader of Latin the most irritating pecularity of this system of dating is that the days after the Ides of any month carry the name of the following month... Another trap for the unwary lies in the fact that the Roman calendars given in most reference books are Julian, not pre-Julian. When Caesar added ten days to the Roman year he put them near the ends of the seven 29-day months, one or two in each. As a result, instead of the day after the Ides of all months being a.d. XVII Kal., in these seven months it is either a.d. XVIII Kal. or a.d. XIX Kal., and all the following days change correspondingly.
- 2011, Robert A. Kaster trans. Macrobius, Saturnalia, Book I, Chapter xiv, Section 8:
- [March, May, Quintilis, and October] also have their Nones on the seventh, as Numa ordained, because Julius changed nothing about them. As for January, Sextilis, and December, they still have their Nones on the fifth, though they began to have thirty-one days after Caesar added two days to each, and it is nineteen days from their Ides to the following Kalends, because in adding the two days Caesar did not want to insert them before either the Nones or the Ides, lest an unprecedented postponement mar religious observance associated with the Nones or Ides themselves, which have a fixed date.
- The third day before the ides of March is March 13th; the third ides of August is August 11th; and the third of the ides of November is November 11th.
English use of the Roman calendrical term always employs the Romans' inclusive dating, including the ides itself when counting. Thus, the "third day before the ides of March" (a.d. iii Id. Mart.) is March 13th: two days before March 15th, not three.
English usage also often follows the Latin contraction of the phrasing, which omits the words ante diem. March 13th may appear as the "third ides of March" or the "third of the ides of March". Thus, the "second ides" (pridie idus) is the 14th day of the old long months and the 12th day of the other months; the "third ides" (tertia idus) is the day before that; the "fourth ides" is the day before that; and so on until the "eighth ides", which is preceded by the nones in every month.
- plural of