Java Year From getYearFromDay(int days)

Description

Converts the number of elapsed days from 0001/01/01 (YYYY/MM/DD) to the corresponding year.

License

Apache License

Parameter

Parameter	Description
days	the number of elapsed days

Return

the corresponded year

Declaration

public static int getYearFromDay(int days) 

Method Source Code

//package com.java2s;
/**//  w ww .  j  ava 2 s. c  o  m
 * Copyright 2011-2017 Asakusa Framework Team.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

public class Main {
    private static final int DAYS_YEAR = 365;
    private static final int YEARS_LEAP_CYCLE = 400;
    private static final int DAYS_LEAP_CYCLE = DAYS_YEAR * YEARS_LEAP_CYCLE + (YEARS_LEAP_CYCLE / 4)
            - (YEARS_LEAP_CYCLE / 100) + (YEARS_LEAP_CYCLE / 400);
    private static final int YEARS_CENTURY = 100;
    private static final int DAYS_CENTURY = DAYS_YEAR * YEARS_CENTURY + (YEARS_CENTURY / 4) - (YEARS_CENTURY / 100)
            + (YEARS_CENTURY / 400);
    private static final int YEARS_LEAP = 4;
    private static final int DAYS_LEAP = DAYS_YEAR * YEARS_LEAP + (YEARS_LEAP / 4) - (YEARS_LEAP / 100)
            + (YEARS_LEAP / 400);

    /**
     * Converts the number of elapsed days from {@code 0001/01/01 (YYYY/MM/DD)} to the corresponding year.
     * @param days the number of elapsed days
     * @return the corresponded year
     */
    public static int getYearFromDay(int days) {

        // the number of leap year cycles (400years)
        int cycles = days / DAYS_LEAP_CYCLE;
        int cycleRest = days % DAYS_LEAP_CYCLE;

        // the century offset in the current leap year cycle (0-3)
        int centInCycle = cycleRest / DAYS_CENTURY;
        int centRest = cycleRest % DAYS_CENTURY;
        centRest += DAYS_CENTURY * (centInCycle / (YEARS_LEAP_CYCLE / YEARS_CENTURY));
        centInCycle -= (centInCycle / (YEARS_LEAP_CYCLE / YEARS_CENTURY));

        // the leap year offset in the current century (0-24)
        int leapInCent = centRest / DAYS_LEAP;
        int leapRest = centRest % DAYS_LEAP;

        // the year offset since the last leap year (0-3)
        int yearInLeap = leapRest / DAYS_YEAR;
        yearInLeap -= (yearInLeap / YEARS_LEAP);

        // compute the year
        int year = YEARS_LEAP_CYCLE * cycles + YEARS_CENTURY * centInCycle + YEARS_LEAP * leapInCent + yearInLeap
                + 1;

        return year;
    }
}

Related

1. getYear(int num)
2. getYear(long t)
3. getYearBegin(int year)
4. getYearFirst(int year)
5. getYearFormat(String dateString)
6. getYearFromISODate(String isoDate)
7. getYearFromTimestamp(long ms)
8. getYearFromWeekCode(String weekCode)
9. getYearFromYM(String ym)