Thunderbird Lightning + Google Calendar

Thunderbird (TB) is the popular mail client from Mozilla.

Lightning is the mozilla add-on to integrate a calendar in TB. It also exists as a standalone project named Sundbird.


If you need to store calendars on a central repository (for example to access them from different places), you may already have used Google Calendar.

• 
  Provider for Google Calendar
  Allows bidirectional access to Google Calendar
  


• 
  mozilla wiki help page
  


• 
  another help/tutorial page