Feature Rich Cross-Platform Calendar Application: Rainlendar2

Rainlendar2 is a calendar application with lots of features which works on Windows, Linux and Mac OSX.

What I like about it, other than being cross-platform, is that you can import an holidays ICAL to it, the way it integrates into the Gnome desktop (screenshot above) and the Google Calendar like reminders. Rainlendar2 comes also with skins and lots of options.