Android - How to enable silent mode during calendar events?

Llama will let you do this, and it is free (Tasker costs money). It has many of the features as Tasker and Locale, and it can even use Locale plugins. I have grown fond of this app and have set up many automated events.

To do this in Llama, you create two events and two profiles.

Profiles

1. Create a new profile and name it something like "No Notifications". Uncheck all of the volume options except for Change notification volume. Set the volume level to 0.
2. Create a second profile and name it "Normal". Again, uncheck all volume options except for Change notification volume. This time, set the volume level to whatever you want, like 5/7.

Events

1. Create a new event.
2. Under Actions, click Add Condition and select Calendar Event. Use the defaults.
3. Next, click Add Action. Select Profile and choose your silent profile.
4. Create a second event. This one will be the opposite of your first event, so change the condition of the calendar to "Event finished/Not current event" and set the action profile to your normal profile.

The developer of Llama is still working on it and adding new features, and you can get details here.

Tasker will do this for you. It allows you to automate tasks when certain conditions are met (and is a truly awesome app). Tasker works by monitoring Contexts and then performing Tasks when those contexts match the conditions you set. Contexts and Tasks are grouped together to create Profiles.

You can set up a Tasker Profile with the Calendar Event Context (set to whatever conditions meet your needs, e.g. "From my Google Calendar [Calendar]," "When event shows me as [busy]," and/or "With title [Title]") and a Task containing Silent Mode > On.

You can find more information about Tasker from the Tasker Homepage and from the Tasker Wiki.

You can try Silent!. It's a very easy app to put your phone insilent mode.

It has a schedule plus a white list (to prevent you from losing important calls). It also has a location option; so it turns your phone to silent mode only if you're in a specified place. It's very simple to use and doesn't need a lot of configurations to work.