This of course stands for the final judgement, but also for all judgements that God brings in. He judged Babylon, Greece, Rome.
How could God, who made the sun and moon partly for signs, not use them to signify the end of the world? What sign could they give that the end of the world was near? It would be entirely appropriate if they were to withdraw their light. This would also be a fitting judgment upon mankind who has come to trust in the permanence and stability of the physical world far more than he trusts in the Lord. Nothing could be more calculated to strike terror into his heart than the failure of what he has come to see as the source of life on earth – our local star. Luke describes the state of those living at the time of Christ’s second coming, ‘men’s hearts failing them from fear and the expectation of those things which are coming on the earth, for the powers of heaven will be shaken’ (Luke 21:26). The cause of men’s fear will not just be social upheaval, the fall of earth’s rulers, but the failure of the heavenly bodies and fear for the ability of the earth itself to continue. This is a fitting judgment on those who have worshipped the creature more than the Creator.