I hate to sound cynical but I don't think it's possible. I'm usually the first person to say 'why not? It could happen!' but not on this one.
Time isn't exactly a physical place you can just return to.
Could you really magically undo ever thought, feeling, action, thing constructed, plant grown, birth, death etc and 'rewind' to a point in time before it happened? Time is a label attached by humans to measure the difference between one instance and others, or the difference between all instances from the first, the beginning of consciously recorded time.
I don't think an elaborate machine can enable time travel any more than everyone suddenly deciding to walk backwards.