JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://momentjs.com/downloads/moment.min.js"></script>
<div><label>Start date</label></div><div><input id="startdate" value="08/24/2014"/></div>
<div><label>Start time</label></div><div><input id="starttime" value="11:00"/></div>
<div><label>End date</label></div><div><input id="enddate" value="08/26/2014"/></div>
<div><label>End time</label></div><div><input id="endtime" value="11:0"/></div>
<div><b><label>RESULT</label></b></div><div><input id="result"/></div>

JavaScript

$( "#endtime" ).keyup(function() {
    var startdt = new Date($("#startdate").val() + " " + $("#starttime").val());
    
    var enddt = new Date($("#enddate").val() + " " + $("#endtime").val());

    var diff = enddt - startdt;
    
    var days = Math.floor(diff / (1000 * 60 * 60 * 24));
    diff -=  days * (1000 * 60 * 60 * 24);
    
    var hours = Math.floor(diff / (1000 * 60 * 60));
    diff -= hours * (1000 * 60 * 60);
    
    var mins = Math.floor(diff / (1000 * 60));
    diff -= mins * (1000 * 60);
    
    var seconds = Math.floor(diff / (1000));
    diff -= seconds * (1000);
    
    $("#result").val(days + " days : " + hours + " hours : " + mins + " minutes : " + seconds + " seconds");
    
})