“Secret things belong to God”. That's a scripture. There are things we don't know. But what we do know has been revealed to us by Our Lord and Savior Jesus Christ, in order for us to work out our soul salvation. Why does Augustine or any other faithful disciple need to be perplexed about what God did NOT reveal?
If Augustine were a faithful follower there is no reason for him to be perplexed about time. Jesus Christ is the Alpha and the Omega, the Beginning and the End. Christians KNOW that they have eternal life. When we pass from this world, we go to be with our King. What s there to be perplexed about?
Instead of pondering about what time is, we should be focused on being ready for that day when the angel appears and says “... time, time shall be no more”. When will that day come? IT'S A SECRET!!