code: public void propertyChange(PropertyChangeEvent evt)
      {
          if (JCalendarPopup.DATE_PARAM.equalsIgnoreCase(evt.getPropertyName()))
              if (evt.getNewValue() instanceof java.util.Date)
          {
              this.setControlValue(evt.getNewValue());
          }
      }
docs: This method gets called when a bound property is changed.
  @param evt A PropertyChangeEvent object describing the event source and the property that has changed.