BRG-Kalender abonnieren
https://www.google.com/calendar/ical/kalender.brg%40gmail.com/public/basic.ics
https://www.google.com/calendar/ical/kalender.brg%40gmail.com/public/full.ics
ICS Adresse zum Abonnieren in Thunderbird Lightning
stadt-bremerhaven.de/thunderbird-mit-dem-google-kalender-synchronisieren
https://addons.mozilla.org/de/thunderbird/addon/provider-for-google-calendar/
https://support.google.com/calendar/answer/37648?hl=de
www.chip.de/artikel/Thunderbird-mit-dem-Google-Kalender-synchronisieren-wie-geht-s_58664553.html