void move(int delta) {
        try {
            DateFormat df = new SimpleDateFormat("yyyy/MM/dd");
            Date d = df.parse(currentDate);
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(d);
            calendar.add(Calendar.DATE, delta);

            DateFormat df2 = new SimpleDateFormat("yyyy/MM/dd（E）");
            currentDate = df2.format(calendar.getTime());
            lblDate.setText(currentDate);
        } catch (ParseException e) {
            throw new RuntimeException(e);
        }
    }