JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://code.jquery.com/jquery-2.0.0.min.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/moment.js/1.7.2/moment.min.js"></script>
<input data-bind="value: startTime" type="Time" ></input>
<output id=startTime data-bind="text: startTime"></output>
<br />
<input data-bind="value: endTime" type="Time"></input>
<output id=endTime data-bind="text: endTime"></output>
<pre data-bind="text: ko.toJSON($data, null, 2)"></pre>

JavaScript

viewModel = {
    //reset startTime and EndTime
    startTime: ko.observable(moment().format('DD HH:mm:ss')),
    endTime: ko.observable(moment().format('DD HH:mm:ss')),
    timeDiff : ko.computed(function () {
      console.log(this.startTime);
      console.log(this.endTime);
      return  moment.duration(this.endTime - this.startTime).humanize();

    })
};

ko.applyBindings(viewModel);