A free app for Android, by Wiki Tech.

Do you ever feel like you want to turn off your phone’s ringer but not the whole thing? Or maybe you just want to set a specific time for silent mode? If so, this app is for you. 

The Auto Silent Scheduler app is an Android app that allows you to automatically set the silent and vibration mode of your phone. This is extremely useful if you have to be quiet in a certain place or situation, like in a meeting or while sleeping.

The app will also let you turn off the screen completely. This way, you can use the phone without having to worry about whether or not the screen will turn off.