How to automatically shutdown your computer at a specific time.

This is a very handy feature that one can use. Not only can you shutdown your computer at a specified time, you can also restart it as well.

Command line
On any linux distribution you will have to obtain elevated privileges first. This can be done by typing su and pressing enter. However, on Ubuntu, you will have to use the sudo command.
The command is:
sudo shutdown -h hh:mm on Ubuntu
shutdown -h hh:mm on other Linux distributions. (after getting elevated privileges).





You have to put in the time at which you want the computer to shutdown in 24 hour format. Here is a screenshot showing you how to do this.

Figure: The shutdown command in action!

The command can be easily cancelled with the following command:

sudo shutdown -c on ubuntu

shutdown -c on other distributions (after obtaining elevated privileges first)

If you wish to reboot your computer, you can substitute shutdown with reboot.

GUI
KShutdown is a GUI tool that allows you to do all of this and more. It should be available in your repositories.

Figure: KShutdown and its options
You can see that there are a wide range of options available. Under extras you can choose to close individual applications as well.
Enjoy!