U can u can go anytime of the day or night
You can go in the Old Chateau more than once.
you cant get him you can only get him in platinum Actually you go to the old Chateau witch is right beside route 205
go to old chateau
Go to old chateau at 8pm and go to the TV
the old chateau in diamond is in the eterna forest. fly to eterna city then go left to eterna forest. but you have to cut the trees before you could go in to the old chateau.
beat the 2nd gym leader go to enterna forest from enterna city then you will see some trees for cut, cut them, then go forward all the way you will be at the old chateau
when you see people in the old chateau there ghosts look at there feet the float and disappear go to the tv room to find rotom at a certain time i think its 8pm and after
go to the old chateau at night and thump the tv
After you get the national pokedex go in the old chateau at eterna forest and go to the TV in there at nighttime.
Get the national dex and get all eight gym badges. You need the HM Cut. Go to Eterna Forest.Go to the Old Chateau. Go to the floor with a TV.Click on it.It will ask you if you want to battle Rotom.Press yes and battle it. It's only of little level.You might get it in one turn with ultra balls.Whatever you do don't use master ball!!!!!!!!!!!Hope I helped.Faysal
There is no "getting past Old Chateau", mainly because that's just a abandoned mansion, and that it's totally optional to go there. What you should focus on is getting all the Gym Badges and defeating the Elite Four and the Champion, who is surprisingly Cynthia, the person who gave you the SecretPotion so you could get to Celestic Town. Then, after you do that, you can go explore Old Chateau.
The only Pokemon you will see in OLD CHATEAU are Gastly. Unless you go to room and bump TV and get Rotom. Also if you have game slot you can catch Gengar in the room with the changing picture.