Acts 1:7

οὐχ ὑμῶν ἐστίν, it does not belong to you, it is not your business. This sense of the genitive, implying property or propriety, is not uncommon in classical Greek. During the tutelage, as it may be called, of His disciples, Jesus constantly avoided giving a direct answer to the inquiries which they addressed to Him. He checked in this way their tendency to speculate on the future and drew their minds to their duty in the present. Cf. John 21:21-22. Of this conduct Chrysostom writes: διδασκάλου γὰρ τοῦτό ἐστι, μὴ ἃ βούλεται ὁ μαθητὴς�' ἃ συμφέρει μαθεῖν, διδάσκειν.

καιρούς. Vulg. ‘momenta.’ This word differs from χρόνος in being restricted to some well-defined point of time, while χρόνος embraces a more extended period. Cf. LXX. Nehemiah 10:34, where the wood for the altar is to be brought εἰς�' ἐνιαυτόν, = at fixed points of time chosen out of larger periods, year by year. The A.V. has ‘at times appointed year by year.’ Cf. also for the idea of the words LXX. 2 Samuel 20:5, καὶ ἐχρόνησεν�, ‘he tarried longer than the set time which he had appointed him’ (A.V.). The two nouns are found in conjunction LXX. Daniel 2:21; Daniel 7:12. Also in 1 Thessalonians 5:1.

ἐξουσίᾳ = authority, absolute disposal. ‘Which the Father appointed by His own authority.’ It is not the same word as that in the next verse, δύναμις, though the A.V. renders both by ‘power.’