title: Returning the exact date difference without using DateDiff
body: <p>I need to return the exact difference between two dates in the form of a string.  </p>
  
  <p>If the dates are <code>01-FEB-2012</code> and <code>01-FEB-2014</code>, the function should return "<em>2 years</em>".<br>
  If the dates are <code>01-FEB-2012</code> and <code>01-MAR-2014</code>, the function should return "<em>25 months</em>".<br>
  If the difference is not in exact years or months, it should return the difference in days.  </p>
  
  <p>I do not want to use <code>DateDiff</code> from the Visual Basic namespace so the code is portable to C#.</p>