you're right, the current calendar implementation is not very handy for your use case. Could you please open an enhancement request in the issue tracker ?
By the way, the datatype ezdate implementation stores the date with a timestamp, so it's limited to a date between the 1st january 1970 and somewhere in 2038 which can be inadequate for a date of birth. If you hit this limitation, you can use the birthday extension which doesn't have this limitation and also has another GUI to fill date (3 drop down selects).
