Great question. I'd go back to the last day my grandmother was coherent. My mother came to take me to a movie, while I was away she had had her first stroke. All alone. I would go back so I could be with her. I would stay home and not leave.
it's only for 10 minutes, but I'm pretty sure if I went back at the right time I could make it so I couldn't go to the theatre, thus ending up staying home! Win :)