title: How to compare DateTime values, taking into account timezone?
body: <p>I have two <code>DateTime</code> variables. Each has a timezone stored in the variable so that when I <code>ToString</code> with format including zzz I get a string including <code>+01:00</code>.</p>
  
  <p>At design time I do not know what the timezones will be and I am expecting the variables to have different timezones from each other.</p>
  
  <p>I want to compare the two <code>DateTime</code> values so that I know which is more recent.</p>
  
  <p>For example, if variable A is <code>2015-07-04T02:00:00+03:00</code> and variable B is <code>2015-07-03T18:00:00-07:00</code> then B > A.</p>
  
  <p>What do I write in C# to tell me this? (I would prefer not to use a third party library.)</p>
  
  <p>(To the SO question-closing zealots: I have spent several hours investigating this using Google, MSDN and SO and am confused. I cannot find a very similar question to this on SO. I am confident that answers to this question will help others.)</p>