''<p>christer.ohlin [[#question-1494352|said]]</p>'' <blockquote>How do I transfer birthdays of family and friends from Address Book to Thunderbird's calendar? </blockquote> I don't know how this works in general, but if you have your Google Contacts, with birthdays for the contacts, added as a CardDAV address book, then add Google calendar as a CalDAV calendar, one of the available calendars, besides the usual one for events, is the Birthdays calendar. Both Contacts and the calendar can be added with built-in options.