With the myriad of calendar applications, both in the cloud (e.g. Google Calendar, Mobile Me, etc.) and running locally (e.g. Sunbird, iCal, Outlook, etc.), the ability to move data between applications can be critical. In order to provide the most seamless experience possible, Google Calendar provides tools for transferring data to and from other applications using the standard iCalendar (.ics) format.
For detailed information on how to export data from Google Calendar, visit the Export your calendar page.
For detailed information on how to import and export data with Google Calendar, visit the Import events page.
The Google Calendar Help Center also contains information on how to keep your calendars synchronized.