Private Sub GetCurrentDateFromTextField (DateString As String) As Long
Try
Dim ticks As Long = DateTime.DateParse(DateString)
If DateTime.GetYear(ticks) >= minYear And DateTime.GetYear(ticks) <= maxYear Then
Return ticks
End If
Catch
'invalid date
End Try 'ignore
Return 0
End Sub
And zero is a valid number of ticks for a date (1/1/1970).
Maybe GetCurrentDateFromTextField should return an Object and so you can return a different value (Null) for an invalid date.