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.

Heaven" and "heavens" are used many times in the Bible, with a couple of variations of meaning. Sometimes it is relatively literal, including times when the Lord is identified with it (“Our Father, who art in the heavens,” for instance), meaning heaven as the eternal home for people who chose to do what is good in this life and let the Lord lead them to a love of being good. In other references, particularly when it is paired with “earth” or other lesser ideas (“In the beginning God created the heavens and the earth,” for instance), “heaven” or “heavens” means our internal life as opposed to our external life. In a way, these two meanings are really the same. If you think about the importance of your deepest thoughts and feelings, you can see that they are the “real” you, much more so than your body is. The relationship between the spiritual world and the natural world is similar; the spiritual world is the “real” one, and controls the natural world the same way our thoughts and feeling control our actions. So in both cases, “heaven” describes a deeper reality that we will enter fully after we die.