Oh fucking hell; special relativity. I'll try and walk through the time travel shenanigans.
You can see a star 1 light year away. Light takes a year to travel from that star to you. So you are seeing that star a year in the past. If you were to teleport to that star; without retaining your "Frame of reference" ((Note, in special relativity, there is no "Fixed frame of reference", meaning that everything in the universe has a different perception, whether slight or otherwise, of the fluidity of time)), then you would arrive at the star, one year into your future. Then, if you were to teleport back, but this time, retaining the stars frame of reference, you would appear one year into your future; as in the first instance, it would be like traveling truely instantly, and in the second instance, you would be travelling at light speed, instantly, your passage would accelerate time to match your perception of it; for you, it would be instant, for your home, it would take a year.