Exception</CODE> will be thrown with a message indicating implementation limits
 if implementation capacities are exceeded.</p>
 
 <p>A <code>null</code> value indicates that field isnot set.</p>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>isPositive</CODE> - Set to <code>false</code> to create a negative duration. When the length
   of the duration is zero, this parameter will be ignored.<DD><CODE>day</CODE> - Day of <code>Duration</code>.<DD><CODE>hour</CODE> - Hour of <code>Duration</code>.<DD><CODE>