If you want to show your birthday on the calendar do the following

  • edit your profile settings (click User CP on left side of green bar at top)
  • enter month and day of birth, and year if desired
  • below that for privay select "Display age and full date of birth", or if you don't want to show your age use "Display only day and month of birth"
  • click save changes
Go browse the Calendar (in the middle of the green bar at top) to see it.

I must have tried to be more careful with the personal info and had it set to "display only age" so it couldn't show my birthday.