'Darkness' in the Bible

The sun shall be turned into darkness, And the moon into blood, Before the day of the Lord come, That great and notable day .

And now, behold, the hand of the Lord is upon thee, and thou shalt be blind, not seeing the sun for a season. And immediately there fell on him a mist and a darkness; and he went about seeking some to lead him by the hand.

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