public static void Main()
var duration = TimeSpan.FromDays(3).Add(TimeSpan.FromHours(9));
var convertedString = System.Xml.XmlConvert.ToString(duration);
Console.WriteLine("converted TimeSpan: " + convertedString);
var iso8601String = "PT72H";
var convertedTimeSpan = System.Xml.XmlConvert.ToTimeSpan(iso8601String);
Console.WriteLine("converted iso8601 string: "+ convertedTimeSpan);