Date/Birthday fields and LDAP schemas

In Thunderbird we have recently added the capability to store/display 
birthdays in the address book. What isn't supported yet is using it 
within LDAP address books.

I had a look around at the various LDAP schemas a while back and 
couldn't find any date/birthday format already defined. Although having 
just thought about it again, I guess the modifytimestamp is a date field.

Even so, does anyone know of existing schemas that define a birthday 
field and/or date format? I'd like to see if we can use something that 
already exists rather than define our own.

Standard8