Hi
=DATEDIF(BirthDate,TODAY(),"y")
to get the current age in years.
=DATEDIF(BirthDate,TODAY(),"ym")
to get months over full years.
=DATEDIF(BirthDate,TODAY(),"y")
to get days over full months.
(there may be some inaccuracies due variable month lengths for last 2
formulas for specific dates as function 2 first parameters).