code: private void labelYearIndicatorMousePressed(MouseEvent e) {
          // If the year menu is disabled, then return.
          if (settings.getEnableYearMenu() == false) {
              return;
          }
          // Create and show the year menu.
          int firstYearDifference = -11;
          int lastYearDifference = +11;
          JPopupMenu yearPopupMenu = new JPopupMenu();
          for (int yearDifference = firstYearDifference; yearDifference <= lastYearDifference;
              ++yearDifference) {
              // No special processing is required for the BC to AD transition in the 
              // ISO 8601 calendar system. Year zero does exist in this system.
              // This try block handles exceptions that can occur at LocalDate.MAX.
              try {
                  YearMonth choiceYearMonth = displayedYearMonth.plusYears(yearDifference);
                  String choiceYearMonthString = "" + choiceYearMonth.getYear();
                  yearPopupMenu.add(new JMenuItem(new AbstractAction(choiceYearMonthString) {
                      @Override
                      public void actionPerformed(ActionEvent e) {
                          String chosenMenuText = ((JMenuItem) e.getSource()).getText();
                          int chosenYear = Integer.parseInt(chosenMenuText);
                          drawCalendar(chosenYear, displayedYearMonth.getMonth());
                      }
                  }));
              } catch (Exception ex) {
              }
          }
          String choiceOtherYearString = "( . . . )";
          yearPopupMenu.add(new JMenuItem(new AbstractAction(choiceOtherYearString) {
              @Override
              public void actionPerformed(ActionEvent e) {
                  otherYearMenuItemClicked();
              }
          }));
          Point menuLocation = getMonthOrYearMenuLocation(labelYear, yearPopupMenu);
          yearPopupMenu.show(monthAndYearInnerPanel, menuLocation.x, menuLocation.y);
      }
docs: labelYearIndicatorMousePressed, This event is called any time that the user clicks on the
  year display label in the calendar. This opens a menu that the user can use to select a new
  year within a chosen range of the previously displayed year.