Wonder if this specific to the Samsung contact app or Android in general. Go to gmail and add a birthday for one of your contacts, but enter month and day only. There's a few people I don't know the age/year of birth, but do know month and day. Wait for your phone to sync the contact and try selecting it. Crashes my contact app. When looking at the export .csv file from google, full birthdays have mm/dd/yy format, partial birthdays have --mm-dd.