Module Module1

    Public Sub main()
        Dim day1 As Date
        Dim day2 As Date
        day1 = DateTime.Parse("2000/05/05")
        day2 = Now
        Console.WriteLine(age(day1, day2).ToString)
        Console.Read()
    End Sub

    '年齢を計算する
    Private Function age(ByVal start As Date, ByVal last As Date) As Long
        If ((start.Month * 100 + start.Day) <= (last.Month * 100 + last.Day)) Then
            Return DateDiff(DateInterval.Year, start, last)
        Else
            Return DateDiff(DateInterval.Year, start, last) - 1
        End If
    End Function

End Module

Private Function age(ByVal start As Date, ByVal last As Date) As Long
	Dim start_ar() As String
	Dim last_ar() As String
	start_ar = Split(start, "/")
	last_ar = Split(last, "/")

	If ((start_ar(1) * 100 + start_ar(2)) <= (last_ar(1) * 100 + last_ar(2))) Then
		age = CInt(DateDiff("yyyy", start, last))
	Else
		age = CInt(DateDiff("yyyy", start, last)) - 1
	End If
End Function