bĭnoctĭum, ii, n. [bis-nox],
a period or space of two nights , two nights (post-Aug and rare; perh. only in the two foll. exs.), * Tac. A. 3, 71: biduum et binoctium, Amm. 30, 1, 8.
binoctium ī, n bi- + nox, a space of two nights , Ta. ...
An Elementary Latin Dictionary