to be honest with you I dont see why the time should be any different between people with differet speed. at 12:0:02 what you see is the picture of traveler at 12:0:01 at 2x miles away which makes you think he is 1 sec yourger than he really is. but the reality is he is at 3x miles away and is 1sec older than you see.
if you can travel faster than light, you actually can chase the light which was sent out yesterday or the past. so you can see the past. But I dont think that means time goes back.
when we see a star, we see its picture probably million years ago because the light took long time to get to our eye. but what that star really looks like at the time you see it actually is different from what you see.
anyway I dont think time changes depending on the speed you travel. also I dont beleive people become younger if they travel in high speed.