Darkness in the Bible can signify mourning (Jeremiah 4:27–28), God’s judgment (Exodus 10:21–23; Isaiah 13:9–13; Jeremiah 13:16; Joel 2:10; Joel 3:14–15; Amos 5:18; Amos 5:20; Amos 8:9–10), the great day of the Lord (Mark 13:24), or a new beginning (Genesis 1:2; Job 38:17; Psalm 74:12–20). Darkness does not indicate God’s absence.1
Given the fact that Jesus tied his coming death to the Passover (Mark 14:22–25) it is best to understand the darkness as symbolizing God’s judgment. That is to say, the three hours of darkness during Jesus’ crucifixion were a visual confirmation that Jesus was busy experiencing God’s anger and judgment against sin. This darkness comes at the sixth hour (12:00), the time when one would expect the sun to shine at its most brightest.
33 And when the sixth hour had come, there was darkness over the whole land until the ninth hour.