C. S. Lewis
 "I certainly believe that to be 
God is to enjoy an infinite present where nothing has 
passed away and nothing is still to come. Does it follow that 
we can say the same of saints and angels? 
To make the life of the blessed 
dead strictly timeless is inconsistent with the 
resurrection of the body."
C.S. Lewis       Time
The debate concerning God and time is between two opposing views; is eternity for God unlimited time or timelessness? 
The Bible literally defines eternity as unlimited time. Timelessness in God is a contradiction to his existence before the creation of the world. Logical fallacies and verses taken out of context are used in attempts to prove that timelessness is Biblical.
C.S. Lewis explains how we can comprehend timelessness.
In his chapter on time, in Mere Christianity, Lewis makes a clear distinction between how we experience time in contrast to how God experiences it. Later he acknowledges that his view of "eternal timelessness" is in contradiction to the promise of God that we will share eternity with him. 

Lewis: “Our life comes to us moment by moment. One moment disappears before the next comes along: and there is room for very little in each. That is what Time is like. And of course you and I tend to take it for granted that this Time series—this arrangement of past, present, and future—is not simply the way life comes to us but the way all things really exist. We tend to assume that the whole universe and God Himself are always moving on from past to future just as we do.”--p.146
Lewis: “God, I believe, does not live in a Time-series at all. His life is not dribbled out moment by moment like ours: with Him it is still 1920 and already 1960."--p.147
In contradiction to scripture, Lewis states that God has no history.
“This human life in God is from our point of view a particular period in the history of our world (from the year A.D. one till the Crucifixion). We therefore imagine it is also a period in the history of God's own existence. But God has no history. He is too completely and utterly real to have one. For, of course, to have a history means losing part of your reality (because it had already slipped away into the past) and not yet having another part (because it is still in the future): in fact having nothing but the tiny little present, which has gone before you can speak about it. God forbid we should think God was like that.”--p.148  

Lewis begins with the same type of false argument that Augustine does, he 
violates the rule of definition. Augustine wrongly defines time as "something" that 
is created, rather than a attribute of an active Creator and a characteristic of the world he has created. Augustine saw eternity as having no past and no future. Lewis says that God has no "history" because he is "too real" to have one; and defines history as the process of "losing part of your reality" because it is in the past and "not yet having another part" of your reality because it's still in the future. The truth is just the opposite, a not real person and a not real God have no history, and only a real person and a real God can create one. 

Augustine: “In the Eternal...nothing passes away, but the whole is simultaneously present. But no temporal process is wholly simultaneous...all time past is forced to move on by the incoming future...all the future follows from the past; and that all, past and future, is created and issues out of that which is forever present. Who will hold the heart of man that it may stand still and see how the eternity which always stands still is itself neither future nor past but expresses itself in the times that are future and past?”--Confessions

The reason Lewis begins this way is because he echoes Augustine’s discourse on time and eternity and he wants to divert our minds from a consistent line of thought.
To say that the Biblical God has "no history" is absolutely unbiblical and absurd. God's history is a record of God's activity, he created the world, he flooded the world with water, he delivered Israel from Egypt. The whole story of the Bible is the History of God at work in redemption. Lewis tells us that time and history involves a process of loosing "reality" and because God  is "utterly real" he cannot possibly have a history. One wonders why Lewis believes this is true in light of what the Bible says. But, like Augustine, Lewis is following the Greek philosophy of Plato.

Plato: "We must make a distinction and ask, What is that which always is and has no becoming; and what is that which is always becoming and never is? That which is apprehended by intelligence and reason is always in the same state; but that which is conceived by opinion with the help of sensation and without reason, is always in a process of becoming and perishing and never really is."--Timaeus

We are not free or finite if God knows our future.
Lewis points out a problem with the view that God is in time but utterly turns it around. It is not the view that "God is in time" that is the basis for questioning human freedom, it is the view that "God is timeless" that is the basis for this question. 

Lewis: "Another difficulty we get if we believe God to be in time is this. Everyone who believes in God at all believes that He knows what you and I are going to do tomorrow. But if He knows I am going to do so-and-so, how can I be free to do otherwise?"--p.148

This is a substitution of the logical question from the classic argument since Augustine that Lewis has been following. The difficulty is not how can we be free if God can see our future, it is, how can God see our future if  we exist only "moment by moment"? We live only moment by moment because we are finite. If God can see our future then the logical conclusion is that we are also eternal and infinite. As Augustine was asked, “if it was the eternal will of God that the creation should come to be, why, then, is not the creation itself also from eternity?" The simplest way to state the logic involved is: If God can see our future from eternity, then we are eternal. If  we are not eternal, then God cannot see our future from eternity.

To believe that we exist only “moment by moment” and that God sees, for all eternity, our entire existence is impossible and an absolute contradiction. Even God cannot see what does not exist or is yet uncreated. "For, of course, to have a history means losing part of your reality (because it had already slipped away into the past) and not yet having another part (because it is still in the future)". If, as Lewis points out, our future activity is "not yet" then he should have logically concluded that it is not knowable regardless if God is in a timeline or not.

Lewis: "The difficulty comes from thinking that God is progressing along the 
Time--line like us: the only difference being that He can see ahead and we cannot. Well, if that were true, if God foresaw our acts, it would be very hard to understand how we could be free not to do them. But suppose God is outside and above the Time-line. In that case, what we call 'tomorrow' is visible to Him in just the same way as what we call 'today.' All the days are 'Now' for Him. He does not remember you doing things yesterday; He simply sees you doing them...He does not 'foresee' you doing things tomorrow; He simply sees you doing them: because, though tomorrow is not yet there for you, it is for Him."--p.148  

Lewis makes the error of substituting the subject of his argument. 
Lewis says, “Lets imagine that God is outside and above the Time-line;” the next logical step is to say that "all God’s days" are “Now” for God. Instead, Lewis says, “All of our days" are “Now” for God. In order for our past and future, to be seen as an eternal present, we would have to imagine that we are outside and above the 
Time-line. If we are in the time-line, God can only see us "moment by moment" If we put this as a simple equation it would look like this: 
If time-line = events are moment by moment  

if no time-line = all events are now 

then God + time-line = God’s events are moment by moment 

then God + no time-line = all God’s events are now 

then man + time-line = man’s events are moment by moment 

then man + no time-line = all man’s events are now 
Lewis creates a fallacy by incorrectly substituting “man” for “God” as the 
subject in the second part of his equation and incorrectly states:
God + no time-line = all man’s events are now 

It’s irrational to believe that we can exist in a future that only God can see and still be considered finite or temporal. If it is true that our entire future is knowable then human rationality can not help us understand God nor eternal reality. But, Lewis strongly affirms the importance of proper reasoning in his book, Miracles.

Lewis: “All possible knowledge depends on the validity of reasoning. If the feeling of certainty which we express by words like must be and therefore and since is a real perception of how things outside our own minds really "must" be, well and good. But if this certainty is merely a feeling in our own minds and not a genuine insight into realities beyond them—if it merely represents the way our minds happens to work—then we can have no knowledge. Unless human reasoning is valid no science can be true."--Miracles
Lewis used reasoning to defeat the arguments of atheism in his book, Miracles. But then nullifies reasoning in his defense of a timeless eternity in his book, Mere Christianity. Lewis and others who follow the theology of God's timelessness know that it contradicts the Biblical account of creation and his active participation in human history. But they merely explain it is impossible for us to know how this could be true because our minds are only finite. We must apply the following remarks to the theology of "God's timelessness" as Lewis did to the theory of "naturalism".

Lewis: “It follows that no account of the universe can be true unless that account leaves it possible for our thinking to be a real insight. A theory which explained everything else in the whole universe but which 'made it impossible to believe that our thinking was valid, would be utterly out of court. For that theory would itself have been reached by thinking, and if thinking is not valid that theory would, of course, be itself demolished. It would have destroyed its own credentials. It would be an argument which proved that no argument was sound—a proof that there are no such things as proofs—which is nonsense."--Miracles
Unless noted, all 
C.S. Lewis quotes are 
from Mere Christianity, 
Macmillan Company, 
 New York, 1970  Edition. 
Book IV. Chapter 3, 
Time and Beyond Time, 
 pages 145-149.