Seconds Passed since a point in time

Since I was not able to find a pertinent calculator for seconds passed since a point in time, here's one implemented in ASP.NET/C#:

Please enter a point in time in the format yyyyMMddhhmmss, for example 20051231235959 for the last second of 2005:

Here's the source code:


    
    string theDate = tbDateInput.Text;
            System.IFormatProvider format 
    = 
         System.Globalization.CultureInfo.InvariantCulture, true;
                string expectedformat 
                = 
    "yyyyMMddHHmmss";

            DateTime startDate 
    = DateTime.ParseExact(theDate,
                expectedformat, format, System.Globalization.
                DateTimeStyles.AllowWhiteSpaces
                );


            TimeSpan sp = DateTime.Now - startDate;
            lblResult.Text =
                    String.Format("{0} seconds have passed since {1}",
                sp.TotalSeconds,
                startDate.ToLongDateString () + "
                                " 
    + startDate.ToLongTimeString ());