// 2020-12-31
        Calendar calendar = Calendar.getInstance();
        calendar.set(2020, Calendar.DECEMBER, 31);
        Date date = calendar.getTime();

        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        String dateStr = format.format(date);
        System.out.println(dateStr);
        // 2020-12-31

        // 2020-12-31
        Calendar calendar = Calendar.getInstance();
        calendar.set(2020, Calendar.DECEMBER, 31);
        Date date = calendar.getTime();

        SimpleDateFormat format = new SimpleDateFormat("YYYY-MM-dd");
        String dateStr = format.format(date);
        System.out.println(dateStr);
        // 2021-12-31

        // 2020-12-31
        LocalDate date = LocalDate.of(2020, 12, 31);
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("YYYY-MM-dd");
        String dateStr = date.format(formatter);
        System.out.println(dateStr);
        // 2021-12-31

        // 2020-12-27
        LocalDate date = LocalDate.of(2020, 12, 27);
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("YYYY-MM-dd");
        String dateStr = date.format(formatter);
        System.out.println(dateStr);
        // 2021-12-27

    /**
     * The year within the era.
     * <p>
     * This represents the concept of the year within the era.
     * This field is typically used with {@link #ERA}.
     * <p>
     * The standard mental model for a date is based on three concepts - year, month and day.
     * These map onto the {@code YEAR}, {@code MONTH_OF_YEAR} and {@code DAY_OF_MONTH} fields.
     * Note that there is no reference to eras.
     * The full model for a date requires four concepts - era, year, month and day. These map onto
     * the {@code ERA}, {@code YEAR_OF_ERA}, {@code MONTH_OF_YEAR} and {@code DAY_OF_MONTH} fields.
     * Whether this field or {@code YEAR} is used depends on which mental model is being used.
     * See {@link ChronoLocalDate} for more discussion on this topic.
     * <p>
     * In the default ISO calendar system, there are two eras defined, 'BCE' and 'CE'.
     * The era 'CE' is the one currently in use and year-of-era runs from 1 to the maximum value.
     * The era 'BCE' is the previous era, and the year-of-era runs backwards.
     * <p>
     * For example, subtracting a year each time yield the following:<br>
     * - year-proleptic 2  = 'CE' year-of-era 2<br>
     * - year-proleptic 1  = 'CE' year-of-era 1<br>
     * - year-proleptic 0  = 'BCE' year-of-era 1<br>
     * - year-proleptic -1 = 'BCE' year-of-era 2<br>
     * <p>
     * Note that the ISO-8601 standard does not actually define eras.
     * Note also that the ISO eras do not align with the well-known AD/BC eras due to the
     * change between the Julian and Gregorian calendar systems.
     * <p>
     * Non-ISO calendar systems should implement this field using the most recognized
     * year-of-era value for users of the calendar system.
     * Since most calendar systems have only two eras, the year-of-era numbering approach
     * will typically be the same as that used by the ISO calendar system.
     * The year-of-era value should typically always be positive, however this is not required.
     */
    YEAR_OF_ERA("YearOfEra", YEARS, FOREVER, ValueRange.of(1, Year.MAX_VALUE, Year.MAX_VALUE + 1)),

    /**
     * Prints or parses a localized pattern from a localized field.
     * The specific formatter and parameters is not selected until the
     * the field is to be printed or parsed.
     * The locale is needed to select the proper WeekFields from which
     * the field for day-of-week, week-of-month, or week-of-year is selected.
     */
    static final class WeekBasedFieldPrinterParser implements DateTimePrinterParser {