V 14-19 "And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years: And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so. And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also. And God set them in the firmament of the heaven to give light upon the earth, And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good. And the evening and the morning were the fourth day.”
Wait a minute!? Hasn't God already (back in day 1) created a separation between light and darkness? Yes, He did. But there it was bringing divine light into a scene that was dark, waste and empty. God is Light (1 John) and what He is and what He does can never be characterized by darkness. So a Christian romance ought to never be characterized by moral darkness.
But now, in day 4, already having that moral light, and a separation between it and darkness, there is something else: the division between day and night. Let's consider that day suggests the thought of work and activity, while night would suggest a time of inactivity and rest. "1 must work the works of him that sent me, while it is day: the night cometh, when no man can work" (in. 9:4).