Information regarding XMLGregorianCalendar
<p>I came across the class <a href="http://download.oracle.com/javase/6/docs/api/javax/xml/datatype/XMLGregorianCalendar.html" rel="nofollow"><code>XMLGregorianCalendar</code></a> today.<br>
I searched in Google regarding its usage but did not find any satisfying answer.</p>

<p>Hence can anyone answer the following questions?</p>

<ol>
<li>What is <code>XMLGregorianCalendar</code>?</li>
<li>What is the usage of this class?</li>
<li>How it is different from <code>GregorianCalendar</code> or both of them are related?</li>
</ol>
