title: date.setHours() not working
body: <p>I am trying to subtract hours from a given date time string using javascript.
  My code is like:</p>
  
  <pre><code>     var cbTime = new Date();    
       cbTime = selectedTime.setHours(-5.5);
  </code></pre>
  
  <p>Where <code>selectedTime</code> is the given time (time that i pass as parameter).</p>
  
  <p>So suppose <code>selectedTime</code>  is <code>Tue Sep 16 19:15:16 UTC+0530 2014</code>
   Ans I get is : <code>1410875116995</code></p>
  
  <p>I want answer in datetime format.
  Am I doing something wrong here? Or there is some other solution?</p>