How long ago does land have to be stolen for it to be recognized as belonging to the new owner? If you show that I have your family heirloom (but in no way sho

How long ago does land have to be stolen for it to be recognized as belonging to the new owner? If you show that I have your family heirloom (but in no way show I was the one who took it, that question is still open), how long must I have held onto it for it to be mine?