Auto Shutdown the System
A simple command can be entered in the Terminal to schedule a time for the system to shut down.
Go to Applications (or Main Menu) > Accessories > Terminal.
Enter sudo shutdown -h +m (replace m with the number of minutes, e.g. +60).
OR: enter sudo shutdown -h hh:mm (replace hh:mm with the time on the 24hr clock, e.g. 23:15).
Enter password and minimize the Terminal window.
The system will then shut down within the minutes or at the time specified. To cancel a scheduled time, enter sudo shutdown -c in the Terminal.