code: @Override
      public String marshal(Calendar object) {
  
          if (object instanceof GregorianCalendar) {
  
              GregorianCalendar cal = (GregorianCalendar) object;
  
              DATE_FORMAT.get().setCalendar(cal);
              String str = DATE_FORMAT.get().format(cal.getTime());
  
              String printableDateString = str.substring(0, 26) + ":" + str.substring(26) + "["
                      + cal.getTimeZone().getID() + "]";
              return printableDateString;
          } else {
              throw new IllegalArgumentException("CalendarStringBinding can only support "
                      + GregorianCalendar.class.getSimpleName());
          }
      }
docs: {@inheritDoc}