JSFiddle - React, Tailwind, and code Playground

HTML

<input id="start" value="01/17/2012 11:20" />
<input id="end" value="01/18/2012 11:20" />
<input id="result" value="Result" />

JavaScript

var start_actual_time = $("#start").val();
    var end_actual_time = $("#end").val();

    start_actual_time = new Date(start_actual_time);
    end_actual_time = new Date(end_actual_time);

    var diff = end_actual_time - start_actual_time;

    var diffSeconds = diff / 1000;
    var HH = Math.floor(diffSeconds / 3600);
    var MM = Math.floor(diffSeconds % 3600) / 60;

    var formatted = ((HH < 10) ? ("0" + HH) : HH) + ":" + ((MM < 10) ? ("0" + MM) : MM)
   $('#result').val(formatted);