Apple disabled Java Applets in browsers, not Java applications but Calendar is written in Objective C not Java and iCal is not supported in OS X 10.8. In OS X 10.8 the application is called Calendar. Your previous comment about the Apply got me to searching and the only place I can find an Apply button in OS X 10.8 is in System Preferences. Apply is not used in Calendar. If you are running OS X 10.8.x and using an application named iCal and/or it has an Apply button, you should consider reinstalling Mountain Lion. By-the-way Calendar on iOS 6.1.2 also uses Done, but the button is at the top of the window and not at the bottom as in OS X 10.8.
