private void fillBoxes() {
        for (int i = -5; i <= 5; i++) {
            cmbYear.addItem(calendar.get(Calendar.YEAR) + i);
        }
        for (int j = 1; j <= 12; j++) {
            cmbMonth.addItem(j);
        }
        cmbYear.setSelectedItem(calendar.get(Calendar.YEAR));
        cmbMonth.setSelectedItem(calendar.get(Calendar.MONTH) + 1);
        cmbYear.addActionListener(changeListener);
        cmbMonth.addActionListener(changeListener);
    }