Moment JS, UTC to Local time

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/moment.js/2.5.1/moment.min.js"></script>
<table>
    <tr>
       <td>Start time: 
       <input class="start" type="text" title="start time" value="2015-09-30 00:00">
       </td>
       <td>
       End time:
       <input class="end" type="text" title="end time" value="2015-10-01 15:53">
       </td>        
       <td>
       Duration:
       <input class="duration" type="text" title="duration">
       </td>        
       
    </tr>

JavaScript

$(document).ready(function() {
      var start_time = $('.start').val(),
        end_time = $('.end').val(),
        d1 = moment(start_time, "YYYY-MM-DD HH:mm"),
        d2 = moment(end_time, "YYYY-MM-DD HH:mm"),
        duration = d2.diff(d1, 'hours') + 1,
        $input = $('.duration');
      if ($input.val() === ''){
	  	$input.val(duration);
      }
   });