At the moment, birthdays that appear in Google Calendar are based on Google Contacts information, but manual creation is now coming.
At the moment, birthdays that appear in Google Calendar are based on Google Contacts information, but manual creation is now coming.
They already have your birthday (and maiden name) through your friends’ contacts.
Being able to add birtdays manually is definitely useful, altough I believe it’s better and more organized to add them through contacts. (Not that I actually use Google contacts/calendar.)