Using relativity, time travel to future is possible. if an object travels at the speed that is as high as a considerable fraction of lightspeed as compared to other object, the time felt by both the objects would be different. The object with high velocity would feel much less time. this way it can travel to future. But going back to past would be impossible because to do so the object need to travel with the speed greater then lightspeed. Although if we talk about relative time, the object that was traveling with less velocity, is already in past if object with more velocity is taken as standard.