title: radix argument must be between 2 and 36 on moment date
body: <p>I'm trying to parse a moment date, specifically this: <code>2018-12-31 00:00:00</code> into a particular format. The problem is that I got this error:</p>
  
  <blockquote>
    <p>toString() radix argument must be between 2 and 36
        at Number.toString ()</p>
  </blockquote>
  
  <p>this is my code:</p>
  
  <pre><code>function format_date(event, addHours){
      var date = event.start.format('YYYY-MM-DD HH:mm:ss');
      var timeFormat = 'h:mm tt';
      var hours = addHours ? ' ' + timeFormat : '';
      return Date.parse(date).toString('dd/MM/yyyy' + hours);
  }
  </code></pre>
  
  <p>the object <code>event</code> is provided by <a href="https://fullcalendar.io/" rel="nofollow noreferrer">fullcalendar</a> when an event is clicked. Each event is composed by a <code>start</code> and an <code>end</code> date. I checked also both dates with <code>isValid</code> method provided by <code>momentjs</code>, and both are valid.</p>
  
  <p>I also have the variable <code>timeFormat</code> which specify the time format, and <code>hours</code> specify if add also the hours to the final date.</p>