Perhaps we will understand what has been written if we deal with a Gospel text spoken by the Savior, which expresses it in this way: “Work while it is day. The night comes when no one can work.” He has named here as this age the day—but of necessity I have added the word here, for I know that in other passages other meanings are revealed—so he has called this age the day, but the darkness and the night the consummation because of punishments. For “why do you desire the Day of the Lord? And it is darkness and not light,” says the prophet Amos. If you can envision after the consummation of the world what the gloom is, a gloom that pursues nearly all of the race of humans who are punished for sins. The atmosphere will become dark at that time, and no longer can anyone ever give glory to God, since the Word has given orders to the righteous saying, go, “my people, enter into your rooms, shut the door, hide yourself for a little season, until the force of my anger has passed away.”
Source: HOMILIES ON JEREMIAH 12