title: How to use JDK GregorianCalendar object dates with Joda
body: <p>I'm trying to use Joda library since count periods with Java native methods is a pain in the neck and all my attempts give unprecise results</p>
  
  <p>I have seen this sample to </p>
  
  <pre><code>int n = Days.daysBetween(start.toLocalDate(), end.toLocalDate()).getDays();
  </code></pre>
  
  <p>since all my classes manage GregorianCalendar, I need that method that counts the days support GregorianCalendar, something like</p>
  
  <pre><code> public int countDays(GregorianCalendar start, GregorianCalendar end){
       //convert to joda start and end
       ...
       return Days.daysBetween(start.toLocalDate(), end.toLocalDate()).getDays();
   }
  </code></pre>
  
  <p>So my question:
  How to convert and reconvert <code>GregorianCalendar</code> object to the object managed by Joda without side effects? </p>