The scroll bar is blocking the add an event button for my Mac
In OSX Lion and Mountain Lion the scroll bar default may be blocking the add an event button on your calendar. To change the scroll bar configuration follow these steps on your Mac:
1. Launch System Preferences from the Apple Menu.
2. When the System Preferences menu opens select General
3. In the middle of the General Preferences window select "Show Scroll Bars: Always"
4. The Scroll Bar will now always be visible, allowing you to click the Add an Event button.