In Genesis 8:22, this signifies the alternating states in intellectual matters of a regenerate person. (Arcana Coelestia 936)

In Isaiah 13:6 and Jeremiah 6:4, this stands for the state associated with that particular time. (Arcana Coelestia 23, 487)

936. 'Day and night' means the state of the same person, that is, of one who is regenerate, as regards things belonging to his understanding, which alternate as day and night do. This is clear from what has just been stated. Summer and winter have reference to things of the will because like things of the will, they are manifestations of heat and of cold, whereas day and night have reference to things of the understanding because, like things of the understanding, they are manifestations of light and darkness. Since these matters are self-evident there is no need to confirm them from similar examples in the Word.