Diffrence between two Date

Private Sub DetermineNumberofDays()
Dim dtStartDate As Date = Convert.ToDateTime(System.DateTime.Now.ToString("MM/dd/yyyy"))
Dim dtEndDate As Date = Convert.ToDateTime(strExpirydate)
Dim tsTimeSpan As TimeSpan
Dim iNumberOfDays As Integer
Dim strMsgText As String


tsTimeSpan = dtEndDate.Subtract(dtStartDate)

iNumberOfDays = tsTimeSpan.Days
strMsgText = "Your trial copy have" & iNumberOfDays.ToString() & "days left."
MsgBox(strMsgText)

End Sub