Before the Times Created by God, Times Were Not
15 But if the roving thought of any one should wander through the images of bygone time, and wonder that You, the God Almighty, and All-creating, and All-sustaining, the Architect of heaven and earth, for innumerable ages refrained from so great a work before You would make it, let him awake and consider that he wonders at false things. For whence could innumerable ages pass by which You did not make, since You are the Author and Creator of all ages? Or what times should those be which were not made by You? Or how should they pass by if they had not been? Since, therefore, You are the Creator of all times, if any time was before You made heaven and earth, why is it said that You refrained from working? For that very time You made, nor could times pass by before You made times. But if before heaven and earth there was no time, why is it asked, What were You doing then? For there was no “then” when time was not.
16. Nor dost Thou by time precede time; else would not Thou precede all times. But in the excellency of an ever-present eternity, Thou precedest all times past, and survivest all future times, because they are future, and when they have come they will be past; but “You are the same, and Your years shall have no end.” Your years neither go nor come; but ours both go and come, that all may come. All Your years stand at once since they do stand; nor were they when departing excluded by coming years, because they pass not away; but all these of ours shall be when all shall cease to be. Your years are one day, and Your day is not daily, but today; because Your today yields not with tomorrow, for neither does it follow yesterday. Your today is eternity; therefore You begot the Co-eternal, to whom You said, “This day have I begotten You.” You have made all time; and before all times You are, nor in any time was there not time.
Source: Confessions (New Advent)