title: Firefox new Date() works for invalid date
body: <p>When I run this in the Firefox console:</p>
  
  <p><code>new Date('25/04/2016')</code></p>
  
  <p>it creates the following date:</p>
  
  <p><code>Date 2018-01-04T05:00:00.000Z</code></p>
  
  <p>It seems to be attempting to add 25 months from <code>01/04/2016</code> and ending up at <code>01/04/2018</code>. Is this expected behavior? I would have expected it to result in an error instead of attempting to parse a nonsensical date.</p>
  
  <p>Chrome returns an invalid date.</p>