Calendar won't open

Calendar app will not open.

The icon doesn't bounce, no windows open up. The top toolbar doesn't even say calendar.

I can right click on the icon and it gives me the option to force quit. So I click that, and no change.

When I try task manager, it says calendar is running.

I've tried all ways of opening it, from every folder and application page I can think of. Sometimes it says: the application Calendar is not open anymore".

Help!