title: DateTime.ParseExact fails
body: <p>The following lines throws a FormatException.</p>
  
  <pre><code>DateTime dateResult;
  System.Globalization.CultureInfo provider = System.Globalization.CultureInfo.InvariantCulture;
  string dateFormat =  "yyyy-MM-dd HH:mm";
  string dateToCheck = "2013-20-10 00:00";
  
  dateResult = DateTime.ParseExact(dateToCheck, dateFormat, provider); // fails
  </code></pre>
  
  <p>It says</p>
  
  <blockquote>
    <p>The DateTime represented by the string is not supported in calendar
    System.Globalization.GregorianCalendar.</p>
  </blockquote>
  
  <p>I can't see what's wrong.</p>