BDC
"Birthday Calendar" (BDC) plugin for Trillian.
Trillian is a gratis multiprotocol instant messaging application that is extendable by plugins. The BDC plugin was the most popular plugin for many consecutive months, and is still a popular download among Trillian plugins.
Trillian BDC is released as open source, free software and available on GitHub. Issues (defects, enhancements) for the BDC plugin are managed in the GitHub issues.