Thanks Blain, for being interested in this scenario of the moon as blood and the sun being dark. The sun is a picture of Christ in the Bible. We read about that in Psalm 19: "In them hath he set a tabernacle for the sun, Which is as a bridegroom coming out of his chamber, and rejoiceth as a strong man to run a race. His going forth is from the end of the heaven, and his circuit unto the ends of it: and there is nothing hid from the heat thereof." Jesus, of course, is the bridegroom and here we seen the sun a picture of him. Jesus is the greater light to rule the day, as it were. And the Bible tells us that as long as Christ is with us, it is called day. We read, "I must work the works of him that sent me, while it is day: the night cometh, when no man can work. As long as I am in the world, I am the light of the world. "
Just as Jesus is pictured as the sun in the Bible, so the law of God is pictured by the moon. We read about the moon as being the lesser light to rule the night. But we also find the Bible talking about the moon and her ordinances. In Jeremiah: "Thus saith the LORD, which giveth the sun for a light by day, and the ordinances of the moon and of the stars for a light by night " Notice that the moon is spoken of as being 'ordinances'. Ordinances is a term for the law of God, as can be seen in Psalm 119.
When the Bible calls the sun dark and the moon blood, it would seem that the Bible is addressing a time when the light of Christ is not available (since the sun is a picture of Christ), and when the law finds people guilty rather than forgiven (since the moon is a picture of the law). This scenario could be said to be characteristic of the unsaved state of being. It might also refer to Jesus on the cross or possible to an end time scenario for the unsaved.