Review for Provider for Google Calendar by Falconer
Rated 1 out of 5 stars
Has stopped working since version 1.0.1 on Thunderbird 31.1.x and 31.2.0. Even 1.0 worked better, despite some hickups.
Recommend going back to version 0.32 which still works great.
To create your own collections, you must have a Mozilla Add-ons account.