code: @Nullable
    public static XMLGregorianCalendar getXMLCalendar (@Nullable final Date aDate)
    {
      if (aDate == null)
        return null;
      return s_aDTFactory.newXMLGregorianCalendar (getCalendar (aDate));
    }
docs: Get the passed {@link Date} as {@link XMLGregorianCalendar}.
  
  @param aDate
  Source date. May be <code>null</code>.
  @return <code>null</code> if the passed date is <code>null</code>.