code: public final void addEventHandler(EventHandler<CalendarEvent> l) {
          if (l != null) {
              if (MODEL.isLoggable(FINER)) {
                  MODEL.finer(getName() + ": adding event handler: " + l); //$NON-NLS-1$
              }
              eventHandlers.add(l);
          }
      }
docs: Adds an event handler for calendar events. Handlers will be called when
  an entry gets added, removed, changes, etc.
  
  @param l the event handler to add