This was in a Japanese Anime Dragon Ball Z but coming the point, the possible reason for that might be that planet might be near to some kind of black hole such that the planet or heaven revolves in a much larger speed than the earth. And because of which the time moves slowly for us, we also age slowly, so 1 day for us is 1 year for our fellows in earth. This problem is of a twin paradox which is: In physics, thetwin paradoxis a thought experiment in special relativity involving identicaltwins, one of whom makes a journey into space in a high-speed rocket and returns home to find that thetwinwho remained on Earth has aged more.