[Daimanta]

Interestingly, some people have administrative birthdays were they are born on an uncertain day of the month which is registered as day 0. So, somebody could be born the 0th of june 1950.

If there is even less information available the same goes for the month of the year. I have seen passports where people are born on 0-0-1970

Must be a frustrating situation in many software systems.