How to add 2 hours for end time on previously "changed" start, using jQuery timepicker?

The jQuery Timepicker I use: http://timepicker.co/

What I want to achieve:

Two time input boxes: start time and end time.
Start Time: 8:00am.
End Time: When start time is changed and set to 8:00am, the end time should automatically be set to 10:00am.

$('#t1').timepicker({
    timeFormat : 'hh:mm a',
    interval : 30,
    minTime : '8',
    maxTime : '11:00 PM',
    startTime : '08:00 AM',
    dynamic : false,
    dropdown : true,
    scrollbar : true
});
$('#t1')
.timepicker('option', 'change', function(time) {
    $('#t2').timepicker('option', 'minTime', time);
    $('#t2').timepicker('setTime', time);
});
$('#t2').timepicker({
    timeFormat : 'hh:mm a',
    interval : 30,
    maxTime : '11:00 PM',
    startTime : '08:00 AM',
    dynamic : false,
    dropdown : true,
    scrollbar : true
});

Everything works well now except the unsettled way to add the 2 hours.

Solution

Use the Date object (time) passed to the #t1 change handler; add 2 hours to that time (in milliseconds, so 2 * 60 * 60 * 1000), and create a new Date() object. Set #t2 based on that.

$('#t1')
  .timepicker('option', 'change', function(time) {
    var later = new Date(time.getTime() + (2 * 60 * 60 * 1000));

    $('#t2').timepicker('option', 'minTime', time);
    $('#t2').timepicker('setTime', later);
  });

$('#t1').timepicker({
  timeFormat: 'hh:mm a',
  interval: 30,
  minTime: '8',
  maxTime: '11:00 PM',
  startTime: '08:00 AM',
  dynamic: false,
  dropdown: true,
  scrollbar: true
});

$('#t1')
  .timepicker('option', 'change', function(time) {
    var later = new Date(time.getTime() + (2 * 60 * 60 * 1000));
    $('#t2').timepicker('option', 'minTime', time);
    $('#t2').timepicker('setTime', later);
  });

$('#t2').timepicker({
  timeFormat: 'hh:mm a',
  interval: 30,
  maxTime: '11:00 PM',
  startTime: '08:00 AM',
  dynamic: false,
  dropdown: true,
  scrollbar: true
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/timepicker/1.3.5/jquery.timepicker.min.js"></script>

<link href="https://cdnjs.cloudflare.com/ajax/libs/timepicker/1.3.5/jquery.timepicker.min.css" rel="stylesheet" />

<input type="text" id="t1" />
<input type="text" id="t2" />