Augustine of Hippo writes:
"Let them see than [sic] that there can be no time apart from creation, and let them cease to talk such nonsense. Let them stretch forth to the things that are before,and let them realize that before all times You are the Eternal Creator of all times, and that no times are co-eternal with You, nor is any creature, even if there were a creature above time" (Augustine, Confessiones 11.XXX).
We also have these words from Anselm of Canterbury:
"Thou wast not, then, yesterday, nor wilt thou be tomorrow; but yesterday and today and tomorrow thou art; or, rather, neither yesterday, nor today nor tomorrow thou art; but, simply, thou art, outside all time. For yesterday and today and tomorrow have no existence, except in time; but thou, although nothing exists without thee, nevertheless dost not exist in space and time, but all things exist in thee" (qt. in Stephen T. Davis' Logic and the Nature of God, p. 9).
But I am inclined to believe that God exists from OLAM to OLAM (Psalm 90:2) in that he exists sempiternally, that is, always in time. The verse found in Psalms indicates that God possibly exists in boundless time. If time has existed forever, then it is possible that God has existed for a temporal eternity: time might be an inherent feature or aspect of God's nature. As Garrett Deweese says, it may be the case that time resides in God.
Furthermore, it is possible that God's time-strand is not exactly conterminous with ours. Our time-strand is part of the created order. Yet it seems that time is ultimately time qua tempus. If the views I have set forth here are correct, then it is possible that "before" and "after" (two successive temporal states) occur in God. Conversely, if God does not somehow work in human history, then it would seem that he is not the Redeemer God. However, I am not espousing some pantheistic or panentheistic vision of Almighty God.
Yet does one want to say that God exists in the space-time continuum which he created? Let us suppose that time is everlasting (it has always existed and always will exist) but was not capable of being counted prior to God's creation of the material universe or his creation of humanity (a suggestion discussed by Stephen T. Davies). That is to say, there could have been a point at which time became discrete or countable. Given these assumptions, it might be said that the same deity is able to act in the now discrete form of time that has been created without being adversely affected by the vicissitudes of time (i.e., the divine experience of time does not result in God's growing old or becoming decrepit). I humbly submit these ideas without being overly dogmatic about any of them.