You can set the time statically or can choice fixed time for turning off your PC . I hope this tiny free software will be very helpful to you. Here is the brief details about this software:
PC Auto shutdown Timer Software That You Must Use
Software system shutdown and restart and Hibernate and Sleep with only two clicks …. 
In this section you can choose a time Choose static time by pressing the corresponding operations (shutdown | | reset | | hibernate | | sleep) system, PC or laptop Taptvn after all that time being one of the four modes These go.
* The amount of time remaining until the operation on the right side of the program is measured in seconds.
* Ability to cancel the quad there.
* You can also select a fixed time (in minutes) to schedule a time to write down in the box and choose the mode of the 4.
* Another interesting possibility is that these programs exist, you have the option of checking the box alarm for last 10 second warning beep at 10 seconds for the system to one of the four to make sound.
* In addition to the above, when the program minimize, you sign in system tray (tray Windows (side sign Hour bottom right window)) in which the right-click on the application you the remaining time until one of the four branches of the view.
Download link: Pc shutdown Timer free
Size:74.00kb
Support: All kinds of windows Os
Version: sutdown timer 1.1, freeware