He appointed the moon for seasons: the sun knoweth his going down.
Psalm 104:19 KJV
Day and night are biblically considered as seasons:
Jeremiah 33:20 KJV
Thus saith the LORD; If ye can break my covenant of the day, and my covenant of the night, and that there should not be day and night in their season;
From the beginning, the moon was appointed for the night season:
Genesis 1:16 KJV
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.
The moon was appointed to rule the night. That’s its season. The moon is used in reference to a wife, while the sun is the husband (Gen 37:9). The bride of Christ (moon) has been appointed a place in heaven next to her husband (the Sun – Psalm 84:11). But her appointment is for rulership of the night season. How do we do that? By allowing the light of the Sun 
to shine through our lives towards those who are dwelling in the night/darkness.
Jesus said that in his kingdom, the rulers are those that serve (Luke 22:25-26). The rulership of the moon is that it shines the light of Christ love into the darkness. This is our appointment, this is our season.
But doesn’t the Psalmist say “seasons”? Indeed he does. Before we stepped into the season where we were shining the light of Christ into the darkness, we were abiding under the light of darkness, shining his light (which is not light at all) through our member:
I speak after the manner of men because of the infirmity of your flesh: for as ye have yielded your members servants to uncleanness and to iniquity unto iniquity; even so now yield your members servants to righteousness unto holiness.
Romans 6:19 KJV
The sun that knows his going down is the devil, he knows that when we come to Christ, the light of his darkness shining through our lives has to go down, even as the sun of righteouness rises. With the rising of Christ in our lives, we are now in a place where our light is no longer to the glory of the kingdom of darkness but rather, to the glory of the kingdom of light.
This is pivotal and makes me think it also belongs under Word Studies, as it teaches the symbolism of the moon, the sun, the husband, the bride and the seasons. I knew of the bride and her husband. The seasons being the lights… that was new for me