title: In Javascript: Why new Date('2012-1-15') - new Date('2012-01-15') == 21600000
body: <p>I'm confused but in javascript:</p>
  
  <pre><code>&gt; new Date('2012-1-15') - new Date('2012-01-15')
    21600000
  </code></pre>
  
  <p>Why is that? (21600000 / 1000 / 3600 == 6 hours)</p>