What then is time? If no one asks me, I know; if I want to explain it to a questioner, I do not know. But at any rate this much I dare affirm I know: that if nothing passed there would be no past time; if nothing were approaching, there would be no future time; if nothing were, there would be no present time.But the two times, past and future, how can they be, since the past is no more and the future is not yet? On the other hand, if the present were always present and never flowed away into the past, it would not be time at all, but eternity. But if the present is only time, because it flows away into the past, how can we say that it is? For it is, only because it will cease to be. Thus we can affirm that time is only in that it tends towards not-being.Sheed Translation of Saint Augustine's Confessions. XI.xiv.