This extension allows Sunbird and Lightning to read and write events to a Google Calendar. Provider for Google Calendar :: Sunbird Add-ons
What this means, is that since I don't maintain a paper calendar, and I pretty much use Google Calendar as my calendar, I've been trying to figure out a way to have a desktop version of the calendar. since I keep my calendar separate from my email client.
With the above extension, I can now add entries to either the Sunbird calendar, or the Google Calendar, and they both end up making changes in the same place!