37. As for the statement that 'the lights will be for signs, and for set times, and for days, and for years', this contains more arcana than can be presented at this point, though no arcanum at all is visible in the sense of the letter. For now only this can be said: Change in spiritual and celestial things takes place both on general and on particular scales, and is comparable to changes that take place through the day and through the year. Changes through the day are from morning to midday, from then on to evening, and through the night to the morning. Changes in the year similar, from spring to summer, from then on to autumn, and through winter to spring. These bring changes in temperature and amount of daylight, and so in the fertility of the earth. Compared to such changes are the changes that take place in spiritual and celestial things. Life without changes and variations would lead to sameness, and so no life at all. Good and truth would not be recognized and identified, let alone perceived. In the Prophets such changes are called 'ordinances', as in Jeremiah,

[Thus] said Jehovah who gives the sun for light by day and the ordinances of the moon and of the stars for light by night, These ordinances will not depart from before Me. Jeremiah 31:35-36.

And in the same prophet,

Thus said Jehovah, If I have not established My covenant of day and night, the ordinances of heaven and earth . . . Jeremiah 33:25.

But these things will in the Lord's Divine mercy be dealt with at Genesis 8:12.

The sun in the Bible represents the Lord, with its heat representing His love and its light representing His wisdom. “Daytime,” then, represents a state in which we are turned toward the Lord, receiving His love and being enlightened by His truth. And “nighttime,” obviously, represents states in which we are turned away from the Lord, left cold and blind to the truth. The most common word used for it in the New Christian theology is “obscurity.” The darkness is not absolute, of course. The light of the moon represents the understanding we can have based on facts and our own intelligence. But while the moon reflects some of the sun's light, it offers almost no heat, so this kind of understanding is a cold one, without the warmth of love. And at its darkest and coldest, night represents a state of judgment. This happens when a person -- or a church -- becomes so mired in evil and falsity that there is no light or heat. The Lord can then step in, separate the good from the evil, consign the evil to hell and begin rebuilding based on the remnant that is still good. Drastic as that sounds, it is something that we all go through repeatedly in various aspects of our loves, so that we can be rid of what is evil and let the Lord rebuild us as angels.