The iPod nano possesses a small time feature that can be use to shut-down you device at a given time. Here's how it works:
- From the Home screen, tap on Clock.
- Flick the screen to the left until you get the "Timer:
- Set the time at which you want to auto shut-down your device and tap on the small "i" button.
- Select "Sleep iPod" from the list and tap on the Set button to validate.