But this day was generally known as Quinquatrus, simply because it was the fifth day after the Ides[164]; i.e. there was a space of three days between the Ides and the festival. Such intervals of three days, either between the Ides and the festival or between one festival and another, occur several times in the Roman calendar[165], though in this instance alone the day following the interval appears in the calendars as Quinquatrus. The term was no doubt a pontifical one, and the meaning was unknown to the common people; in any case it came to be misunderstood, and was in later times popularly applied to the four days following the festival as well as the festival itself; its first syllable being taken to indicate a five-day period instead of the fifth day after the Ides. This popular mistake led to still further confusion owing to a curious change in the religious character of these days, about the nature of which there can be no serious doubt. The 19th came to be considered as sacred to Minerva[166], because a temple to that goddess was consecrated on this day, on the Caelian or the Aventine, or possibly both[167]. There is no obvious connexion between Mars and Minerva; and it is now thought probable that Minerva has here simply taken the place of another goddess, Nerio—one almost lost to sight in historical times, but of whose early connexion with Mars some faint traces are to be found. Thus where we find Minerva brought into close relation with Mars, as in the myth of Anna Perenna, it is thought that we should read Nerio instead of Minerva[168]. This conclusion is strengthened by a note of Porphyrion on Horace _Epist._ ii. 2. 209 ‘Maio mense religio est nubere, et etiam Martio, in quo de nuptiis habito certamine a Minerva Mars victus est: obtenta virginitate Neriene est appellata.’ As Neriene must = Nerio[169], this looks much like an attempt to explain the occurrence of two female names, Minerva and Nerio, in the same story; the original heroine, Nerio, having been supplanted by the later Minerva[170].