birthday versus birthdate

BDAY is described as birthday or birthdate (or date of
birth), but I
think there is a significant difference.

I understand how to use BDAY as a birthdate (or date of
birth) because
you have a year of birth (eg 19 June 1951)

But in my view birthday is only month and date because it
repeats
every year. And some people don't want to disclose their
year of birth
but do want to celebrate their birthday. (eg 19 June).

So has there been any discussion of this or resolution? I
using
microformats in  greatuncle.com

Thanks  - ray daly
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