Arcana Coelestia #21
21. Verses 4-5 And God saw that the light was good; and God made a distinction between the light and the darkness. And God called the light Day, and the darkness He called Night.
The light is called good, because it comes from the Lord, who is good itself. 'The darkness' is those things which were there prior to the person's new conception and birth. They were seen as light, because evil was seen as good, and falsity as truth. But in reality they are darkness and things proper to that person which are lingering on. All things that are the Lord's, being things of light, are compared to the day, and all that are man's own, being those of thick darkness, are compared to the night, as is done many times in the Word.
Arcana Coelestia #2199
2199. That 'well advanced in years' means that the time was at hand follows from what has now been stated. 'A day' in the Word, as also 'a year', and indeed 'time' in general, means state, as shown in 23, 487, 488, 493, 893. Thus: here 'advanced in years' means, in the internal sense, entering that state in which He was to cast off the human, and so means that the time was at hand.