Bede

And Jonathan said to him: Tomorrow is the New Moon, etc. The holy Scripture does not denote those unequal beginnings of the months, which the Romans have annually, twelve in number, but the new moons, which are called Neomenia by the Greeks; which the Hebrews solemnly celebrated according to the institution of the law, with sacrifices, feasts, and the rest of the Sabbath, that is, of rest. …

Commentary on Samuel ↗