Just a small snippet, but an often asked question none the less ;-)
Public Class Person
Public BirthDate As Date
'.... other person data (lastname, first name , etc. )
Public ReadOnly Property Age() As Integer
Get
Dim a As Integer = DateTime.Now.Year - BirthDate.Year
If DateTime.Now.DayOfYear < BirthDate.DayOfYear Then a -= 1
Return a
End Get
End Property
End Class