It was after John had told his father about everything that happened in the past world, and was told he was crazy.
Viewing post in Wanderer of Calamity jam comments
Oh yeah, after that you can change from past to present in the game. And you could either go back to Bed in the Past. to get one of the Endings. Or "wander" around the Present world. But I Highly recommend to just go to bed in the Past as F.O. See the ending first, so you don't miss out on any stuff and then try to get the 2nd Ending. (It's quite complicated ngl)