Use Rainlendar With Sunbird

Rainlendar is a great free desktop calendar program that is available for Windows and Linux. It displays a fully functional calendar right on your desktop and has a load of features. One of its great features is the ability to read other calendar program's .ICS calendar file, this lets you have your entire schedule on you desktop, right at your finger tips. This is great for most calendar programs, put Mozilla's Sunbird program no longer uses the .ICS format for local storage, but it uses it for remote storage.

You can read how to get to Sunbird output it's calendars to .ics so it is compatible with rainlendar, as well as other programs, at the SleepingCats blog .