Converts a provided Julian Day Number (i.e. - Java java.util

Java examples for java.util:Calendar Julian

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Description

Converts a provided Julian Day Number (i.e.

Demo Code

/**// w  ww . j ava 2s. c  o m
 * Persian Calendar see: http://code.google.com/p/persian-calendar/
   Copyright (C) 2012  Mortezaadi@gmail.com
   PersianCalendarUtils.java
           
   Persian Calendar is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

public class Main{
    public static void main(String[] argv) throws Exception{
        long julianDate = 2;
        System.out.println(julianToPersian(julianDate));
    }
    /**
     * Converts a provided Julian Day Number
     * (i.e. the number of days since January 1 in the year 4713 BC) to the Persian (Shamsi) date.
     * Since the Persian calendar is a highly regular calendar, converting to and from a Julian Day Number
     * is not as difficult as it looks. Basically it's a mather of dividing, rounding and multiplying.
     * @param julianDate
     * @return long
     */
    public static long julianToPersian(long julianDate) {
        long persianEpochInJulian = julianDate
                - persianToJulian(475L, 0, 1);
        long cyear = ceil(persianEpochInJulian, 1029983D);
        long ycycle = cyear != 1029982L ? ((long) Math
                .floor((2816D * (double) cyear + 1031337D) / 1028522D))
                : 2820L;
        long year = 474L + 2820L
                * ((long) Math.floor(persianEpochInJulian / 1029983D))
                + ycycle;
        long aux = (1L + julianDate) - persianToJulian(year, 0, 1);
        int month = (int) (aux > 186L ? Math
                .ceil((double) (aux - 6L) / 30D) - 1 : Math
                .ceil((double) aux / 31D) - 1);
        int day = (int) (julianDate - (persianToJulian(year, month, 1) - 1L));
        return (year << 16) | (month << 8) | day;
    }
    /**
     * Converts a provided Persian (Shamsi) date to the Julian Day Number
     *  (i.e. the number of days since January 1 in the year 4713 BC).
     *  Since the Persian calendar is a highly regular calendar, converting to and from a Julian Day Number
     *   is not as difficult as it looks. Basically it's a mather of dividing, rounding and multiplying.
     *   This routine uses Julian Day Number 1948321 as focal point, since that Julian Day Number
     *    corresponds with 1 Farvardin (1) 1. 
     * @param year int persian year
     * @param month int persian month
     * @param day int persian day
     * @return long
     */
    public static long persianToJulian(long year, int month, int day) {
        return 365L
                * ((ceil(year - 474L, 2820D) + 474L) - 1L)
                + ((long) Math
                        .floor((682L * (ceil(year - 474L, 2820D) + 474L) - 110L) / 2816D))
                + (PersianCalendarConstants.PERSIAN_EPOCH - 1L) + 1029983L
                * ((long) Math.floor((year - 474L) / 2820D))
                + (month < 7 ? 31 * month : 30 * month + 6) + day;
    }
    /**
     * Ceil function in original algorithm
     * @param double1
     * @param double2
     * @return long
     */
    public static long ceil(double double1, double double2) {
        return (long) (double1 - double2 * Math.floor(double1 / double2));
    }
}

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