A.M.
If he is still in a crib, I would just ignore the calls and allow him to fall back to sleep. If he is in a converted bed/toddler bed, then it is more difficult. My little one will tear the door down and eventually pull the safety knob off if left, when it is after 5 am. So I pop her quickly into my bed and she then falls back to sleep. If it is unusually early ie 2am, then I try to ignore and most of the time she goes back into her bed. But it is hard for them to really understand at that age what time it is and when they can really get up. Good Luck.