Review for Provider for Google Calendar by Chris Seeling
Rated 5 out of 5 stars
Nice work.
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To set it up I used:
in Thunderbird/calendar pane, right-click and click "New Calendar", "On the Network", "Google Calendar" paste in private address from Google Calendar Settings to get the private address (XML)
hope this helps to get going quickly
To create your own collections, you must have a Mozilla Add-ons account.