I’ve noticed that there are three types of women on facebook.
The first, doesn’t have any birthday information and all it says is “Born” (i assumed as much). Overly paranoid this type must make sure that no age related information is revealed.
The second, leaves out the birth year. Even though she too wants to be seen as young forever, this type wants to make sure that all of facebook wishes her a happy birthday on her birthday, so month and year are necessary.
The third, leaving the full month, day, year, might as well be a man.