Review for Provider for Google Calendar by Cristian Vasile Mocanu
Rated 5 out of 5 stars
This addon is really useful, but it's totally unusable if you also have the ThuderBirthday addon: in the dialog to add a calendar, the page used to choose a Google calendar is empty.
Fortunately, the fix is easy: remove the ThuderBirthday addon since it's not needed anyway: in the new version of "Provider for Google Calendar" you can just synchronize the birthday calendars that Google already has.
To create your own collections, you must have a Mozilla Add-ons account.