Begin here, BOTR. Relativity is all about what different observers see. That is the key understanding. Hawking talks about a ping pong ball bouncing up and down on a single spot on a table on a moving train. To an observer on the train, the ping pong ball will have moved only short vertical distances but to an observer on the ground looking through the windows of the passing train, the ping pong ball will be moving in gentle, elongated arcs and the time the ball is airborne above the table will be perceived as longer. The two observers are moving relative to one another and will assign different times and positions to the same event. No particular observer’s measurements are any more correct than any other observer’s, but all the measurements are related. Neither time nor space is therefore constant.
To your question, God (if He exists) does not keep time because time is relative to who is observing it and from where. If God is ubiquitous, He will perceive time on a scale of zero to infinity. He would see the pingpong ball on the train bouncing up and down and He would see it frozen for all eternity in one place. Time, therefore, does not exist for God.
