I feel you're being pedantic. The misunderstanding is not around the concept of a birthday, yes--it's due to the use of a time-having datetime datatype for thi

I feel you're being pedantic. The misunderstanding is not around the concept of a birthday, yes--it's due to the use of a time-having datetime datatype for this purpose, in UI and/or application server or database layers, the latter of which ought to reject datetimes as nonconforming inputs.