the Date.getMonth() method has bug?
<p>I tested in  chrome and firefox, and here is the problem.
The Date object's <code>getMonth()</code> method has an Bug? 
When I set the location date on someDay, like <code>"2013-1-31"</code></p>

<p>then, the js code is :</p>

<pre><code>var d = new Date();
d.setMonth(8);
d.getMonth();
</code></pre>

<p>The result is "9", why?</p>

<p>I found when the month has 31 days, run the <code>setMonth</code> method and the <code>getMonth</code> method will return wrong value</p>

<p>why?</p>
