DateTime from = new DateTime(2011, 1, 7);
DateTime to = DateTime.Now;
TimeSpan ts = to - from;
Console.WriteLine("start time : {0:yyyy/MM/dd HH:mm:ss}", from);
Console.WriteLine("end time : {0:yyyy/MM/dd HH:mm:ss}", to);
Console.WriteLine("time diff : {0}", ts);
Console.WriteLine("month diff : {0}", (to.Month - from.Month) + 12 * (to.Year - from.Year));
Console.WriteLine("day diff : {0}", ts.TotalDays);
Console.WriteLine("hour difff : {0}", ts.TotalHours);
Console.WriteLine("minutes diff : {0}", ts.TotalMinutes);
Console.WriteLine("second diff : {0}", ts.TotalSeconds);