'Darkness' in the Bible

the sun shall be changed to darkness and the moon to blood, before the great and gloriously appearing day of the Lord come.

And now behold, the Lord's hand is upon thee, and thou shalt be blind, not seeing the sun for a season. And immediately there fell upon him a mist and darkness; and going about he sought persons who should lead him by the hand.

to open their eyes, that they may turn from darkness to light, and from the power of Satan to God, that they may receive remission of sins and inheritance among them that are sanctified by faith in me.