Traveller, if you make your question (regarding the person doing the round trip) such that his speed is just very close to the speed of light it takes away the absolute impossibility and, mathematically, removes aspects of infinity. It is not possible to get to lightspeed.

If someone gets to near lightspeed and travels for a year (his time) then on return he would find the earth had aged much more. If he had travelled very close to lightspeed the earth could have aged many hundreds or thousands of years. If he could actually get to lightspeed this aging would be infinite.

Conversely, if the people on the ground could get a rocket to accelerate fast enough, without crushing the person inside, and got the rocket to close to lightspeed and arranged for the rocket to return, decelerate and land within 1 year, the person on-board may have only experienced a very short trip - perhaps a few minutes. You may notice that this is practically harder because of the high acceleration that the person on-board would have to endure, so perhaps you need to imagine he has a Star Trek type inertial dampener.

Edit: I was replying to Traveller rather than Hamza here.