Note 15 — BOOK I.

“Ἔνη καὶ νέα the last day of the month: elsewhere τριανιὰς. So called for this reason. The old Greek year was lunar; now the moon’s monthly orbit is twenty-nine and a half days. So that if the first month began with the sun and moon together at sunrise, at the month’s end it would be sunset; and the second month would begin at sunset. To prevent this irregularity, Solon made the latter half day belong to the first month; so that this thirtieth day consisted of two halves, one belonging to the old, the other to the new moon. And when the lunar month fell into disuse, the last day of the calendar month was still called Ἔνη καὶ νέα.”—L. & S. Greek Lexicon, in v. ἔνος.