Days, hours, minutes, seconds between two dates

TimeSpan is the object you need:

TimeSpan span = (DateTime.Now - DateTime.Now);

String.Format("{0} days, {1} hours, {2} minutes, {3} seconds", 
    span.Days, span.Hours, span.Minutes, span.Seconds);

When you subtract one DateTime from another, you get a TimeSpan instance, which exposes those values.

TimeSpan diff = DateTime.Now - DateTime.Today;
string formatted = string.Format(
                       CultureInfo.CurrentCulture, 
                       "{0} days, {1} hours, {2} minutes, {3} seconds", 
                       diff.Days, 
                       diff.Hours, 
                       diff.Minutes, 
                       diff.Seconds);