Clifford D. Simak

One world and then another, running like a chain. One world treading on the heels of another world that plodded just ahead. One world's tomorrow, another world's today. And yesterday is tomorrow, and tomorrow is the past. Except, there wasn't any past. No past, that was, except the figment of remembrance that flitted like a night-winged thing in the shadow of one's mind. No past that one could reach. No pictures painted on the wall of time. No film that one could run backwards and see what-once-had-been... One road was open, but another road was closed. Not closed, of course, for it had never been. For there wasn't any past, there never had been any, there wasn't room for one. Where there should have been a past there was another world.