The philosophy of time is a very complex subject. I've put further study of it on hold since I started preparing for a few essay contests on Ayn Rand's philosophy, but a friend recently asked me some questions about it, and I think the following summary I provided is a good indication of where I stand.
While I'm still open to the idea that God is not timeless, the primary problem I have with it is that it seems to be incompatible with even a weak understanding of divine immutability, a doctrine I think is Scripturally supported.
If God is temporal, then an A-series theory of time - which I will explain shortly - is true, and His knowledge literally changes. For example, the proposition "x will occur" would be true until x occurs in time, after which it would be false - so God would know "x will occur" at one point in time but not another. If God's knowledge changes, God changes.
I've tried to construct an argument that God could not be omniscient unless He is timeless, but to be honest, I haven't thought of one which holds. Of course, the meaning of "omniscience" would have to be qualified if God is temporal - it would have to mean something like "knowledge of all propositions which are now true" rather than simply "knowledge of all true propositions[, each of which are unchangingly true]" - but so long as one accepts determinism, God could control under what conditions His knowledge changes.
That's one reason I didn't really like the TF article on time. Parkinson didn't discuss an A-series vs. a B-series view of time, eternal creation, the meaning of omniscience, etc. The discussion is more complicated than "if God's knowledge changes then God is not omniscient," for why couldn't it be the case that God's knowledge changes in accordance with divinely predetermined changes?
Parkinson also doesn't seem to realize omnitemporality traditionally refers to the view that God has an infinitely extended past and future, or at least that He is at all times (contrary to atemporality). He can define omnitemporality in a certain way to make it compatible with Calvinism if he likes, but to me it seems like trying to define free will similarly - it's more likely to confuse than help.
Anyways, for "now," the best argument for divine timelessness I can think of is the argument that it follows from explicit Scriptural testimony of divine immutability. There do appear to be good philosophical arguments against an A-series view of time, however (e.g. McTaggart's paradox), which could also be used as arguments for divine timelessness. I haven't studied those enough to cite them as support for divine timelessness, though.
As for a defense of divine timelessness from counter-arguments, some language used to describe God is anthropomorphic, figures of speech not literally true. This includes words such as "past," "present," "now," and "future." Temporal events are not literally related this way. The A-series view of time says they are and that there is an objective "now." A simple way of thinking about it is to say that the A-series view of time regards some language as irreducibly tensed. So, for instance, a proposition like "I am writing this post now" cannot be reduced to "I write this sentence at 10:51 pm, June 16, 2012." Both may be true, A-series theorists say, but what they each mean is different.
A B-theory view of time, on the other hand, believes events are related by means other than tensed language. Or, at least, any tensed sentence expresses a tenseless meaning (hence, tensed language is non-literal). So in place of words like "past," "present," "now," ""future," yesterday," "today," "tomorrow," "was," will," "did," "had," etc., B-series theorists substitute words like "earlier than," "simultaneous with," and "later than." These substitutes are not tensed phrases. "I write this sentence simultaneous with Jodie driving a car, you sleeping, etc." is not tensed. "I write this sentence later than my reading of your post" is not tensed. No time has a privileged status of "now" or "present" on a B-series view of time. It rather relates events in the direction of logical causation. An event is earlier than another because the earlier event causes the latter event. Events may be caused by other events without its being necessary that they could have been, at some point, modified by the word "now."
If God is timeless and omniscient, a B-series view of time must be true. Otherwise, propositions describing events would be tensed, God would have to know those propositions, and God's knowledge of tensed propositions would necessitate and A-series view of time. This would lead to divine mutability, as shown earlier, which I find problematic.
How does a B-series view of time square with creation? Paul Helm theorizes an "eternal creation." To be eternal is simply to be atemporal or timeless. What does this mean? Well, A and B-series views of time define time in terms of the tensed or tenseless relations events possess (e.g. past/present/future vs. earlier/simultaneous/later). So the point is that God does not acquire [new] relations if He is timeless. What relation[s] God has to the universe, then, must be timeless - that is, on the B-series view of time, these relations cannot be earlier than, simultaneous with, or later than any other events.
Hence, as Helm puts it, God does not will "in" time but rather "with" time; He eternally or timelessly decrees {event A at time t1, B at t2, etc.}. He does not eternally decree {to will event A at time t1, to will B at t2, etc.}. God's will is eternal - it does not occur in time. So the whole temporal order is timeless, though the events in this order are temporal because of their tenseless yet temporal relations with each other (earlier/simultaneous/later).
In my own words, I think of the whole temporal order - the entire B-series - as a set: {A, B, C...}. A is the earliest event (or events) within this order, B is the next, and so on. A causes B, B causes C, and so on. While the entire set is eternally or timelessly created - hence God stands in static relationship to it and the events of the set, none of which possesses the tensed distinction of being "the present" - the set itself is not earlier/simultaneous/later than any other event, for there is no other event to which the creation of the temporal order could stand in [temporal] relation. However, A, B, C, etc. do stand in relation to each other in such a way, which is why we can say such events occur in time. They are earlier/simultaneous/later with respect to each other.
Thus, since there is no earlier event, the creation of the temporal order (the entire B-series set of events) is eternal. The entire created order is metaphysically dependent upon God's will, however (by definition, since created), so that creation would be eternal does not empty the word of its meaning.
If anyone is finding this difficult to understand, don't feel bad. I've read Craig's Time and Eternity (which was very helpful in introducing the material and written by an A-series theorist) Helm's Eternal God, and God and Time: Four Views, and I still have a hard time keeping it straight. I would recommend reading these books. Helm's summary view presented in God and Time: Four Views is viewable on googlebooks. It seems that he updated his views in Eternal God, though (e.g. possible worlds).
