Enforcing shutdowns for my son

This has proved quite a fun challenge. My son has a problem playing video games late at night. We have asked nicely multiple times but it has not worked. I tried using AD to enforce it but that didn’t work since he doesn’t care about the server or the internet. My next tactic was to automatically shut the PC down using a scheduled task. That worked up till he figured out that he could play longer if he switched to a new time zone. My new trick is to change his timezone back to EST every ten minutes using:

Control.exe TIMEDATE.CPL,,/Z Eastern Standard Time

I doubt this will be the final solution but I can’t wait to hear his voice when his PC starts shutting down on him after he knows he has just changed it to GMT.