Plutarch, Quaestiones Romanae
Goodwin, Ed.

Solution. Was it (as most men think, and Livy tells us) because on the next day after the Ides of Quintilis (which they now call July), the tribunes of the soldiery marching forth, the army was conquered by the Gauls in a battle about the river Allia and lost the city, whereupon this day was reckoned unlucky; and superstition (as it loves to do) extended this observation further, and subjected the next days after the Nones and Kalends to the same scrupulosity? Or what if this notion meet with much contradiction? For it was on another day they were defeated in battle, which they call Alliensis (from the river) and greatly abominate as unsuccessful; and whereas there be many unlucky days, they do not observe them in all the months alike, but every one in the month it happens in, and it is most improbable that all the next days after the Nones and Kalends simply considered should contract this superstition. Consider now whether—as they consecrated the first of the months to the Olympic Gods, and the second to the infernals, wherein they solemnize some purifications and funeral rites to the ghosts of the deceased— they have so constituted the three which have been spoken of, as it were, the chief and principal days for festival and holy days, designating the next following these to daemons and deceased persons, which days they esteemed unfortunate and unfit for action. And also the Grecians, worshipping their Gods at the new of the moon, dedicated the next day to heroes and daemons, and the second of the cups was mingled on the behalf of the [p. 218] male and female heroes. Moreover, time is altogether a number; and unity, which is the foundation of a number, is of a divine nature. The number next is two, opposite to the first, and is the first of even numbers. But an even number is defective, imperfect, and indefinite; as again an odd number is determinate, definite, and complete. Therefore the Nones succeed the Kalends on the fifth day, the Ides follow the Nones on the ninth, for odd numbers do determine the beginnings. But those even numbers which are next after the beginnings have not that pre-eminence nor influence; hence on such days they take not any actions or journey in hand. Wherefore that of Themistocles hath reason in it. ‘The Day after the feast contended with the Feast-day, saying that the Feast-day had much labor and toil, but she (the Day after the feast) afforded the fruition of the provision made for the Feast-day, with much leisure and quietness. The Feast-day answered after this wise: Thou speakest truth; but if I had not been, neither hadst thou been.’ These things spake Themistocles to the Athenian officers of the army, who succeeded him, signifying that they could never have made any figure in the world had not he saved the city.

Since therefore every action and journey worth our diligent management requires necessary provision and preparation, but the Romans of old made no family provision on feast-days, nor were careful for any thing but that they might attend divine service,—and this they did with all their might, as even now the priests enjoin them in their proclamations when they proceed to the sacrifices,— in like manner they did not rush presently after their festival solemnities upon a journey or any enterprise (because they were unprovided), but finished that day in contriving domestic affairs and fitting themselves for the intended occasion abroad. And as even at this day, after they have said their prayers and finished their devotion, [p. 219] they are wont to stay and sit still in the temples, so they did not join working days immediately to holy days, but made some interval and distance between them, secular affairs bringing many troubles and distractions along with them.