ThunderCal

Rated 4 out of 5 stars

per Onireon el oct. 16, 2014 · enllaç permanent

A very simple, yet very useful plugin.
If you use Google Calendar, this addon may be a very good alternative to Lightning.
Not a five star review, though, because this addon, as reported by erjati in far 2010, still continues to prevent you to switch between two different Google accounts; once you set the first, it becomes permanent. Reinstalling or playing with the configuration editor will not help you.
To solve this issue, you need to clean Thunderbird cookies as described here: http://blog.onireon.com/thunderbird-and-thundercal-google-account-permanent-seriously/