 possible to represent 
 a <code>java.util.GregorianCalendar</code> daylight savings timezone id in the 
 XML Schema 1.0 date/time datatype representation.</p>
 
 <p>To compute the return value's <code>TimeZone</code> field,
 <ul>
 <li>when <code>this.getTimezone() != FIELD_UNDEFINED</code>,
 create a <code>java.util.TimeZone</code> with a custom timezone id 
 using the <code>this.getTimezone()</code>.</li>
 <li>else use the <code>GregorianCalendar</code> default timezone value 
 for the host is defined as 