title: how to determine if 2 dates object equals each other?
body: <p>this is my 1st question in stackoverflow.</p>
  
  <pre><code>var str="Oct 13,2011";
  var date1=new Date(str);
  var date2=new Date(str);
  </code></pre>
  
  <p>of course
  valueOf(date1)==valueOf(date2)</p>
  
  <p>but why
  date1!=date2</p>
  
  <p>or say,how to determine 2 date object if they equal each other.</p>
  
  <p>Date is a js object </p>