title: Add two dates times together in javascript
body: <p>I am trying to add two dates: </p>
  
  <pre><code>date start Fri Apr 26 2013 16:08:03 GMT+0100 (Paris, Madrid)
  +  
  date periode Fri Apr 26 2013 00:10:00 GMT+0100 (Paris, Madrid)
  </code></pre>
  
  <p>I used this code:</p>
  
  <pre><code>var periode=$("#dure").val();
  var start = $("#start").val()
  var end =$("#end").val();
  
  var dateStart= new Date(start);
  console.log('start');
  console.log(dateStart);
  
  var date=dateStart.format('yyyy-mm-dd'); 
  per=date+' '+periode;
  var datePeriode= new Date(per);
  
  console.log('datePeriode');
  console.log(datePeriode);
  var dateEnd= dateStart.getTime()+datePeriode.getTime();
  console.log('dateEnd');
  console.log(dateEnd);
  </code></pre>
  
  <p>In my JavaScript console, I get:</p>
  
  <pre><code>dateDebut
  Fri Apr 26 2013 16:33:11 GMT+0100 (Paris, Madrid)
  datePeriode
  Fri Apr 26 2013 00:15:00 GMT+0100 (Paris, Madrid)
  dateEnd
  2733922091000
  </code></pre>
  
  <p>How can I fix that?  Am I missing something?</p>