Hide "Birthdays & Anniverseries" calendar from conflict search list
Evolution Preferences > Calendar and Tasks > Meeting Invitations > Conflict search:
Select the calendars to search for meeting conflicts:
Contacts > Birthdays & Anniverseries
Providing that this calender is automatcially generated based on vCard data and cannot have conflicts, as all events there are "transparent", the preferences shall not offer it for consideration when doing meeting schedulings.
Edited by Milan Crha