The idea of God is that He is a maximally great being. That is to say God is the greatest conceivable being that could possibly exist. So what would a maximally great being be like, timeless or temporal? Well if a being is timeless, remember this means it can not interact in time. But clearly God answers our prayers, listens to us, the Son took darktime on a human nature and became a man and died for our sins. Clearly we have a God who interacts in time and a maximally great being would be such a being who would interact with us. So if anything it would make sense for a maximally great being to be temporal (in time) as opposed to timeless and once again we can qualify it by saying that with out creation God was in a state of timelessness but He created He created time and stepped into it .