Since I am currently building a scheduling system that uses a sophisticated (I think) recurrenance system, I am often looking for the easiest way to get total values (minutes, seconds, hours, etc) between 2 values. 

 Per Microsoft: 

DateTime centuryBegin = new DateTime(2001, 1, 1);
DateTime currentDate = DateTime.Now;

long elapsedTicks = currentDate.Ticks - centuryBegin.Ticks;
TimeSpan elapsedSpan = new TimeSpan(elapsedTicks);

Console.WriteLine("Elapsed from the beginning of the century to {0:f}:", 
                   currentDate);
Console.WriteLine("   {0:N0} nanoseconds", elapsedTicks * 100);
Console.WriteLine("   {0:N0} ticks", elapsedTicks);
Console.WriteLine("   {0:N2} seconds", elapsedSpan.TotalSeconds);
Console.WriteLine("   {0:N2} minutes", elapsedSpan.TotalMinutes);
Console.WriteLine("   {0:N0} days, {1} hours, {2} minutes, {3} seconds", 
                  elapsedSpan.Days, elapsedSpan.Hours, 
                  elapsedSpan.Minutes, elapsedSpan.Seconds);
// If run on December 14, 2007, at 15:23, this example displays the
// following output to the console:
//    Elapsed from the beginning of the century to Friday, December 14, 2007 3:23 PM:
//          219,338,580,000,000,000 nanoseconds
//          2,193,385,800,000,000 ticks
//          219,338,580.00 seconds
//          3,655,643.00 minutes 

// 2,538 days, 15 hours, 23 minutes, 0 seconds

Find the microsoft documentation here