http://sufficientlysecure.org/birthday-adapter

Birthday Adapter is the first implementation that displays all birthdays from your contact list automatically in your standard Android calendar without hassle.

License: GPLv3+

Developer: Dominik Schürmann, Marten Gajda (support for Android below 4.0)

Translation: See https://www.transifex.net/projects/p/birthday-adapter/

Libraries/Code