More recent devices have an option in their settings to set the profiles to Automatic, meaning your Device will go to Silent when there’s an active Appointment in your Calendar.

If you don’t want to create appointments or just simply want to switch to a descrete Profile and back to normal after a specific period of time, there’s a simple application that can do that. Download and install Mute4 to your Device and run it. You will be prompted to choose between Silent or Vibrate to activate and a period of time after which your Device will automatically switch back to Normal (in case you are like me and forget about these things).

(Source: XDA Developers)