Psalms 90:4

"For a thousand years in Your sight are but as yesterday, which is past by" [Psalm 90:4]: hence we ought to turn to Your refuge, where You are without any change, from the fleeting scenes around us; since however long a time may be wished for for this life, "a thousand years in Your sight are but as yesterday:" not as tomorrow, which is to come: for all limited periods of time are reckoned as having already passed. Hence the Apostle's choice is rather to aim at what is before, [Philippians 3:13] that is, to desire things eternal, and to forget things behind, by which temporal matters should be understood. But that no one may imagine a thousand years are reckoned by God as one day, as if with God days were so long, when this is only said in contempt of the extent of time: he adds, "and as a watch in the night:" which only lasts three hours. Nevertheless men have ventured to assert their knowledge of times, to the pretenders to which our Lord said, "It is not for you to know the times or seasons, which the Father has put in His own power:" [Acts 1:7] and they allege that this period may be defined six thousand years, as of six days. Nor have they heeded the words, "are but as one day which is past by:" for, when this was uttered, not a thousand years only had passed, and the expression, "as a watch in the night," ought to have warned them that they might not be deceived by the uncertainty of the seasons: for even if the six first days in which God finished His works seemed to give some plausibility to their opinion, six watches, which amount to eighteen hours, will not consist with that opinion.

Do not turn man away into humiliation. And you said: Turn back, sons of men. O Lord, that we might dare to ask this, that we might say, Do not turn man away into humiliation, you have given us confidence by saying: "Return to me, sons, as you turn back, and I will heal your afflictions." And you said: Turn back, sons of men. For a thousand years before your eyes are like a single day that has passed by: do not turn man away into humiliation. And a watch in the night. What did he mean to say by this, And a watch in the night? We ought also to know this according to the literal history: the night is divided into four watches. Indeed in the Gospel too it is said: "But in the fourth watch." One watch, then, is three hours: so the night is divided into four watches. Indeed soldiers have these four stations, when they keep guard and relieve one another. See, then, what he says. All of our eternity: that Adam our forefather, who lived nine hundred and thirty years; even that Methuselah, who lived nine hundred and sixty-five years; suppose he had lived a thousand: in comparison with your eternity, what was great is short. For what can be great that has an end? Our thousand years, before we had committed offense, was one day in your sight. Why do I say, one day? one watch of the night. Do not turn man away into humiliation. See what he says: You deigned for our salvation to come down, you poured out your blood for us: do not allow us to perish, and to die in humiliation. You yourself said: "When I have been lifted up, I will draw all to myself." You have been lifted up, and you have lifted us up: do not abandon us, so that we be dragged down.

And as a watch in the night. The night has four watches, marked off in periods of three hours each, as it is said in the Gospel, "In the fourth watch of the night" Jesus "came to them," which is understood to be about cockcrow. This, then, is what he says: a thousand years with you are to be compared not only to the shortness of a day, but to the span of three hours.

For a thousand years before your eyes are as yesterday's day, which has passed. Compared to the eternity of God, all the time of man is short: although it seems long to us, yet in comparison with eternity, because it is bounded by an end, it is reckoned as nothing.

God will say, at the great day, to those whom he has turned to destruction, Return--Arise you dead. But it might be objected against the doctrine of the resurrection that it is a long time since it was expected and it has not yet come. Let that be no difficulty, for a thousand years, in God's sight, are but as one day.