Hello Joe,
Have you read the module config guide? It goes into detail on how to configure the Scheduled Task to enable birthday emails.
There is a file called "UserDataBirthdayEmail.ascx.resx" which contains the email strings.
All new records default to the current day if they have not been edited (agreed -this is not particulary useful!). This functrionality has not been touched since it was released over 2 years ago and is showing it's age...