Isn't that obvious? The type
System.DataTime
represent a point on a time scale, a unique point in the global history. The type
System.TimeSpan
represents a time interval between to events.
More exactly, in relativity it's better to talk about
time-like intervals. It's good really to understand it from the standpoint of physics:
http://en.wikipedia.org/wiki/Time-like#Time-like_interval[
^].
Please see:
http://msdn.microsoft.com/en-us/library/system.datetime.aspx[
^],
http://msdn.microsoft.com/en-us/library/system.timespan.aspx[
^].
Programming aside, isn't this obvious that you can compare interval with interval (relationship "not longer than") or time point with another time point (relationship "not later than"), but not one with another?
Important hint though:
System.DateTime first = System.DateTime.Now;
System.DateTime second = System.DateTime.Now;
System.TimeSpan interval = second - first;
—SA