LXX Num 9:3

τῇ τεσσαρεσκαιδεκάτῃ ἡμέρᾳ τοῦ μηνὸς τοῦ πρώτου πρὸς ἑσπέραν ποιήσεις αὐτὸ κατὰ καιρούς, κατὰ τὸν νόμον αὐτοῦ καὶ κατὰ τὴν σύνκρισιν αὐτοῦ ποιήσεις αὐτό.

You are to observe it at the appointed time, at twilight on the fourteenth day of this month, in accordance with its statutes and ordinances.”