how to add hours to selected time?

Question

I am using time picker like:

<input type="text" id="time" name="startTime" value="" onblur="changeTime()"> 
<input type="text" id="time1" name="endTime" value="">

$('#time').timepicker({
   'minTime': '9:00am',
   'maxTime': '8:00pm',
  'showDuration': true,
  'step': 15
}); 

If I select the id="time" as 1:00pm then the next id="time1" should contain(+4) i.e.5:00pm

so I tried this in following way but not succeeded.

 function changetime(){
     var endTime= document.getElementById('time').value;
     var temp=Math.abs(endTime.getTime());
     var total=Math.ceil(temp+(4));
     document.getElementById('time1').value=total;
 } 

does anyone know the solution?

Answer 1

Try this.

$('#time').timepicker({
    'minTime': '9:00am',
        'maxTime': '8:00pm',
        'showDuration': true,
        'step': 15
});
$('#time').on('changeTime', function () {
    var temp = $(this).val();
    var hoursMinutes = temp.substring(0, temp.length - 2).split(":");
    var meridian = temp.substring(temp.length - 2).toLowerCase();
    var newMeridian = meridian;
    var newHours = +hoursMinutes[0] + 4;
    var newMinutes = hoursMinutes[1];
    if (newHours >= 12) {
        newMeridian = (meridian ==="pm")? "am" : "pm";
    }
    if (newHours > 12) {
        newHours -= 12;
    }
    var newTime = newHours + ":" + newMinutes + newMeridian;
    $('#time1').val(newTime);
});

Working demo: http://jsfiddle.net/codovations/g2VLQ/1/