Moisés Silva’s discussion (in the New International Dictionary of New Testament Theology and Exegesis) of the Greek word nux (νύξ), night,  offers an insightful treatment on the theological significance of the word especially as used in the Gospel of John.

“The Gospel of John makes this point explicitly in two passages. In connection with the healing of the man who was born blind, Jesus said: ‘As long as it is day, we must do the works of him who sent me. Night is coming, when no one can work. While I am in the world, I am the light of the world’ (John 9:4-5). And in connection with the death of Lazarus, when Jesus decided to go to Judea and the disciples questioned the wisdom of doing so, he explained: ‘Are there not twelve hours of daylight [τῆς ἡμέρας]? Anyone who walks in the daytime [ἐν τῇ ἡμέρᾳ] will not stumble, for they see by this world’s light [τὸ φῶς]. It is when a person walks at night [ἐν τῇ νυκτί] that they stumble, for they have no light [τὸ φῶς]’ (11:9-10). But even when John appears to use νύξ in a simple temporal way, there may be an allusion to spiritual darkness. The unusual piece of information that Nicodemus came to see Jesus by night (3:2, followed by comments on spiritual light and darkness, 3:19-21), with a subsequent repetition of that detail (19:39), seems to suggest a certain ambivalence in Nicodemus’s standing. And it surely is no mere chronological interest when John, after mentioning that Judas took the bread and went out, adds, ‘And it was night’ (13:30).” (Vol. 3, p. 438)


New International Dictionary