iAction is a handy software that helps you automatically shutdown, power off, reboot, suspend or log off computers and executes AppleScripts at schedule time you specifies. It can shut down computers at schedule time when no user is logged in or when computers are in suspended power conservation mode. It gives you different ways to schedule the shutdown event for your needs.
Key features:

Shut down, power off, reboot, shut down monitor, suspend or log off computers at schedule time.
Shut down, power off, reboot, hibernate, suspend or log off computers at schedule time when no user is logged in
Activate computers from suspended power conservation mode, and shut down, power off, reboot, suspend or log off computers at schedule time
Different schedules to meet your needs.
Customize countdown duration during shutdown.