JSFiddle - React, Tailwind, and code Playground

HTML

<span></span>

JavaScript

var start = new Date('2016-05-11 21:00:00');
var end = new Date('2016-05-16 11:50:00');
var diffTimeMilliSeconds = (end - start) / 1000; // milli seconds to seconds 
$('span').html(diffTimeMilliSeconds);