¿Existe alguna biblioteca o algoritmo para el calendario persa (Shamsi o Jalali) en Android? [cerrado]

Quiero convertir la fecha gregoriana (occidental) a la fecha persa (Shamsi) y viceversa para todas las versiones de Android.

¿Existe alguna biblioteca o algoritmo completo y confiable?

Estoy usando este algoritmo durante años y es muy preciso entre 1901 y 2099.

¡Úselo y disfrute! :)

public class Utilities {

    private class SolarCalendar {

        public String strWeekDay = "";
        public String strMonth = "";

        int date;
        int month;
        int year;

        public SolarCalendar()
        {
            Date MiladiDate = new Date();
            calcSolarCalendar(MiladiDate);
        }

        public SolarCalendar(Date MiladiDate)
        {
            calcSolarCalendar(MiladiDate);
        }

        private void calcSolarCalendar(Date MiladiDate) {

            int ld;

            int miladiYear = MiladiDate.getYear() + 1900;
            int miladiMonth = MiladiDate.getMonth() + 1;
            int miladiDate = MiladiDate.getDate();
            int WeekDay = MiladiDate.getDay();

            int[] buf1 = new int[12];
            int[] buf2 = new int[12];

            buf1[0] = 0;
            buf1[1] = 31;
            buf1[2] = 59;
            buf1[3] = 90;
            buf1[4] = 120;
            buf1[5] = 151;
            buf1[6] = 181;
            buf1[7] = 212;
            buf1[8] = 243;
            buf1[9] = 273;
            buf1[10] = 304;
            buf1[11] = 334;

            buf2[0] = 0;
            buf2[1] = 31;
            buf2[2] = 60;
            buf2[3] = 91;
            buf2[4] = 121;
            buf2[5] = 152;
            buf2[6] = 182;
            buf2[7] = 213;
            buf2[8] = 244;
            buf2[9] = 274;
            buf2[10] = 305;
            buf2[11] = 335;

            if ((miladiYear % 4) != 0) {
                date = buf1[miladiMonth - 1] + miladiDate;

                if (date > 79) {
                    date = date - 79;
                    if (date <= 186) {
                        switch (date % 31) {
                        case 0:
                            month = date / 31;
                            date = 31;
                            break;
                        default:
                            month = (date / 31) + 1;
                            date = (date % 31);
                            break;
                        }
                        year = miladiYear - 621;
                    } else {
                        date = date - 186;

                        switch (date % 30) {
                        case 0:
                            month = (date / 30) + 6;
                            date = 30;
                            break;
                        default:
                            month = (date / 30) + 7;
                            date = (date % 30);
                            break;
                        }
                        year = miladiYear - 621;
                    }
                } else {
                    if ((miladiYear > 1996) && (miladiYear % 4) == 1) {
                        ld = 11;
                    } else {
                        ld = 10;
                    }
                    date = date + ld;

                    switch (date % 30) {
                    case 0:
                        month = (date / 30) + 9;
                        date = 30;
                        break;
                    default:
                        month = (date / 30) + 10;
                        date = (date % 30);
                        break;
                    }
                    year = miladiYear - 622;
                }
            } else {
                date = buf2[miladiMonth - 1] + miladiDate;

                if (miladiYear >= 1996) {
                    ld = 79;
                } else {
                    ld = 80;
                }
                if (date > ld) {
                    date = date - ld;

                    if (date <= 186) {
                        switch (date % 31) {
                        case 0:
                            month = (date / 31);
                            date = 31;
                            break;
                        default:
                            month = (date / 31) + 1;
                            date = (date % 31);
                            break;
                        }
                        year = miladiYear - 621;
                    } else {
                        date = date - 186;

                        switch (date % 30) {
                        case 0:
                            month = (date / 30) + 6;
                            date = 30;
                            break;
                        default:
                            month = (date / 30) + 7;
                            date = (date % 30);
                            break;
                        }
                        year = miladiYear - 621;
                    }
                }

                else {
                    date = date + 10;

                    switch (date % 30) {
                    case 0:
                        month = (date / 30) + 9;
                        date = 30;
                        break;
                    default:
                        month = (date / 30) + 10;
                        date = (date % 30);
                        break;
                    }
                    year = miladiYear - 622;
                }

            }

            switch (month) {
            case 1:
                strMonth = "فروردين";
                break;
            case 2:
                strMonth = "ارديبهشت";
                break;
            case 3:
                strMonth = "خرداد";
                break;
            case 4:
                strMonth = "تير";
                break;
            case 5:
                strMonth = "مرداد";
                break;
            case 6:
                strMonth = "شهريور";
                break;
            case 7:
                strMonth = "مهر";
                break;
            case 8:
                strMonth = "آبان";
                break;
            case 9:
                strMonth = "آذر";
                break;
            case 10:
                strMonth = "دي";
                break;
            case 11:
                strMonth = "بهمن";
                break;
            case 12:
                strMonth = "اسفند";
                break;
            }

            switch (WeekDay) {

            case 0:
                strWeekDay = "يکشنبه";
                break;
            case 1:
                strWeekDay = "دوشنبه";
                break;
            case 2:
                strWeekDay = "سه شنبه";
                break;
            case 3:
                strWeekDay = "چهارشنبه";
                break;
            case 4:
                strWeekDay = "پنج شنبه";
                break;
            case 5:
                strWeekDay = "جمعه";
                break;
            case 6:
                strWeekDay = "شنبه";
                break;
            }

        }

    }

    public static String getCurrentShamsidate() {
        Locale loc = new Locale("en_US");
        Utilities util = new Utilities();
        SolarCalendar sc = util.new SolarCalendar();
        return String.valueOf(sc.year) + "/" + String.format(loc, "%02d",
                sc.month) + "/" + String.format(loc, "%02d", sc.date);
    }
}

Creo que esta clase de Java es más fácil de usar y más confiable. Lo encontré en un foro iraní , los iraníes usan el calendario Jalali y lo llaman "Shamsi", que significa calendario solar. esta es la clase Java:

package MyUtil;

import java.util.Calendar;
import java.util.GregorianCalendar;

/**
 * Title: Calender Conversion class
 * Description: Convert Iranian (Jalali), Julian, and Gregorian dates to
 * each other
 * Public Methods Summary:
 * -----------------------
 * JavaSource_Calendar();
 * JavaSource_Calendar(int year, int month, int day);
 * int getIranianYear();
 * int getIranianMonth();
 * int getIranianDay();
 * int getGregorianYear();
 * int getGregorianMonth();
 * int getGregorianDay();
 * int getJulianYear();
 * int getJulianMonth();
 * int getJulianDay();
 * String getIranianDate();
 * String getGregorianDate();
 * String getJulianDate();
 * String getWeekDayStr();
 * String toString();
 * int getDayOfWeek();
 * void nextDay();
 * void nextDay(int days);
 * void previousDay();
 * void previousDay(int days);
 * void setIranianDate(int year, int month, int day);
 * void setGregorianDate(int year, int month, int day);
 * void setJulianDate(int year, int month, int day);
 */
public class CalendarTool {

    /**
     * JavaSource_Calendar:
     * The default constructor uses the current Gregorian date to initialize the
     * other private memebers of the class (Iranian and Julian dates).
     */
    public CalendarTool()
    {
        Calendar calendar = new GregorianCalendar();
        setGregorianDate(calendar.get(Calendar.YEAR),
                calendar.get(Calendar.MONTH)+1,
                calendar.get(Calendar.DAY_OF_MONTH));
    }

    /**
     * JavaSource_Calendar:
     * This constructor receives a Gregorian date and initializes the other private
     * members of the class accordingly.
     * @param year int
     * @param month int
     * @param day int
     */
    public CalendarTool(int year, int month, int day)
    {
        setGregorianDate(year,month,day);
    }

    /**
     * getIranianYear:
     * Returns the 'year' part of the Iranian date.
     * @return int
     */
    public int getIranianYear() {
        return irYear;
    }

    /**
     * getIranianMonth:
     * Returns the 'month' part of the Iranian date.
     * @return int
     */
    public int getIranianMonth() {
        return irMonth;
    }

    /**
     * getIranianDay:
     * Returns the 'day' part of the Iranian date.
     * @return int
     */
    public int getIranianDay() {
        return irDay;
    }

    /**
     * getGregorianYear:
     * Returns the 'year' part of the Gregorian date.
     * @return int
     */
    public int getGregorianYear() {
        return gYear;
    }

    /**
     * getGregorianMonth:
     * Returns the 'month' part of the Gregorian date.
     * @return int
     */
    public int getGregorianMonth() {
        return gMonth;
    }

    /**
     * getGregorianDay:
     * Returns the 'day' part of the Gregorian date.
     * @return int
     */
    public int getGregorianDay() {
        return gDay;
    }

    /**
     * getJulianYear:
     * Returns the 'year' part of the Julian date.
     * @return int
     */
    public int getJulianYear() {
        return juYear;
    }

    /**
     * getJulianMonth:
     * Returns the 'month' part of the Julian date.
     * @return int
     */
    public int getJulianMonth() {
        return juMonth;
    }

    /**
     * getJulianDay()
     * Returns the 'day' part of the Julian date.
     * @return int
     */
    public int getJulianDay() {
        return juDay;
    }

    /**
     * getIranianDate:
     * Returns a string version of Iranian date
     * @return String
     */
    public String getIranianDate()
    {
        return (irYear+"/"+irMonth+"/"+irDay);
    }

    /**
     * getGregorianDate:
     * Returns a string version of Gregorian date
     * @return String
     */
    public String getGregorianDate()
    {
        return (gYear+"/"+gMonth+"/"+gDay);
    }

    /**
     * getJulianDate:
     * Returns a string version of Julian date
     * @return String
     */
    public String getJulianDate()
    {
        return (juYear+"/"+juMonth+"/"+juDay);
    }

    /**
     * getWeekDayStr:
     * Returns the week day name.
     * @return String
     */
    public String getWeekDayStr()
    {
        String weekDayStr[]={
                "Monday",
                "Tuesday",
                "Wednesday",
                "Thursday",
                "Friday",
                "Saturday",
        "Sunday"};
        return (weekDayStr[getDayOfWeek()]);
    }

    /**
     * toString:
     * Overrides the default toString() method to return all dates.
     * @return String
     */
    public String toString()
    {
        return (getWeekDayStr()+
                ", Gregorian:["+getGregorianDate()+
                "], Julian:["+getJulianDate()+
                "], Iranian:["+getIranianDate()+"]");
    }


    /**
     * getDayOfWeek:
     * Returns the week day number. Monday=0..Sunday=6;
     * @return int
     */
    public int getDayOfWeek()
    {
        return (JDN % 7);
    }

    /**
     * nextDay:
     * Go to next julian day number (JDN) and adjusts the other dates.
     */
    public void nextDay()
    {
        JDN++;
        JDNToIranian();
        JDNToJulian();
        JDNToGregorian();
    }
    /**
     * nextDay:
     * Overload the nextDay() method to accept the number of days to go ahead and
     * adjusts the other dates accordingly.
     * @param days int
     */
    public void nextDay(int days)
    {
        JDN+=days;
        JDNToIranian();
        JDNToJulian();
        JDNToGregorian();
    }

    /**
     * previousDay:
     * Go to previous julian day number (JDN) and adjusts the otehr dates.
     */
    public void previousDay()
    {
        JDN--;
        JDNToIranian();
        JDNToJulian();
        JDNToGregorian();
    }

    /**
     * previousDay:
     * Overload the previousDay() method to accept the number of days to go backward
     * and adjusts the other dates accordingly.
     * @param days int
     */
    public void previousDay(int days)
    {
        JDN-=days;
        JDNToIranian();
        JDNToJulian();
        JDNToGregorian();
    }

    /**
     * setIranianDate:
     * Sets the date according to the Iranian calendar and adjusts the other dates.
     * @param year int
     * @param month int
     * @param day int
     */
    public void setIranianDate(int year, int month, int day)
    {
        irYear =year;
        irMonth = month;
        irDay = day;
        JDN = IranianDateToJDN();
        JDNToIranian();
        JDNToJulian();
        JDNToGregorian();
    }

    /**
     * setGregorianDate:
     * Sets the date according to the Gregorian calendar and adjusts the other dates.
     * @param year int
     * @param month int
     * @param day int
     */
    public void setGregorianDate(int year, int month, int day)
    {
        gYear = year;
        gMonth = month;
        gDay = day;
        JDN = gregorianDateToJDN(year,month,day);
        JDNToIranian();
        JDNToJulian();
        JDNToGregorian();
    }

    /**
     * setJulianDate:
     * Sets the date according to the Julian calendar and adjusts the other dates.
     * @param year int
     * @param month int
     * @param day int
     */
    public void setJulianDate(int year, int month, int day)
    {
        juYear = year;
        juMonth = month;
        juDay = day;
        JDN = julianDateToJDN(year,month,day);
        JDNToIranian();
        JDNToJulian();
        JDNToGregorian();
    }

    /**
     * IranianCalendar:
     * This method determines if the Iranian (Jalali) year is leap (366-day long)
     * or is the common year (365 days), and finds the day in March (Gregorian
     * Calendar)of the first day of the Iranian year ('irYear').Iranian year (irYear)
     * ranges from (-61 to 3177).This method will set the following private data
     * members as follows:
     * leap: Number of years since the last leap year (0 to 4)
     * Gy: Gregorian year of the begining of Iranian year
     * march: The March day of Farvardin the 1st (first day of jaYear)
     */
    private void IranianCalendar()
    {
        // Iranian years starting the 33-year rule
        int Breaks[]=
            {-61, 9, 38, 199, 426, 686, 756, 818,1111,1181,
                1210,1635,2060,2097,2192,2262,2324,2394,2456,3178} ;
        int jm,N,leapJ,leapG,jp,j,jump;
        gYear = irYear + 621;
        leapJ = -14;
        jp = Breaks[0];
        // Find the limiting years for the Iranian year 'irYear'
        j=1;
        do{
            jm=Breaks[j];
            jump = jm-jp;
            if (irYear >= jm)
            {
                leapJ += (jump / 33 * 8 + (jump % 33) / 4);
                jp = jm;
            }
            j++;
        } while ((j<20) && (irYear >= jm));
        N = irYear - jp;
        // Find the number of leap years from AD 621 to the begining of the current
        // Iranian year in the Iranian (Jalali) calendar
        leapJ += (N/33 * 8 + ((N % 33) +3)/4);
        if ( ((jump % 33) == 4 ) && ((jump-N)==4))
            leapJ++;
        // And the same in the Gregorian date of Farvardin the first
        leapG = gYear/4 - ((gYear /100 + 1) * 3 / 4) - 150;
        march = 20 + leapJ - leapG;
        // Find how many years have passed since the last leap year
        if ( (jump - N) < 6 )
            N = N - jump + ((jump + 4)/33 * 33);
        leap = (((N+1) % 33)-1) % 4;
        if (leap == -1)
            leap = 4;
    }


    /**
     * IsLeap:
     * This method determines if the Iranian (Jalali) year is leap (366-day long)
     * or is the common year (365 days), and finds the day in March (Gregorian
     * Calendar)of the first day of the Iranian year ('irYear').Iranian year (irYear)
     * ranges from (-61 to 3177).This method will set the following private data
     * members as follows:
     * leap: Number of years since the last leap year (0 to 4)
     * Gy: Gregorian year of the begining of Iranian year
     * march: The March day of Farvardin the 1st (first day of jaYear)
     */
    public boolean IsLeap(int irYear1)
    {
        // Iranian years starting the 33-year rule
        int Breaks[]=
            {-61, 9, 38, 199, 426, 686, 756, 818,1111,1181,
                1210,1635,2060,2097,2192,2262,2324,2394,2456,3178} ;
        int jm,N,leapJ,leapG,jp,j,jump;
        gYear = irYear1 + 621;
        leapJ = -14;
        jp = Breaks[0];
        // Find the limiting years for the Iranian year 'irYear'
        j=1;
        do{
            jm=Breaks[j];
            jump = jm-jp;
            if (irYear1 >= jm)
            {
                leapJ += (jump / 33 * 8 + (jump % 33) / 4);
                jp = jm;
            }
            j++;
        } while ((j<20) && (irYear1 >= jm));
        N = irYear1 - jp;
        // Find the number of leap years from AD 621 to the begining of the current
        // Iranian year in the Iranian (Jalali) calendar
        leapJ += (N/33 * 8 + ((N % 33) +3)/4);
        if ( ((jump % 33) == 4 ) && ((jump-N)==4))
            leapJ++;
        // And the same in the Gregorian date of Farvardin the first
        leapG = gYear/4 - ((gYear /100 + 1) * 3 / 4) - 150;
        march = 20 + leapJ - leapG;
        // Find how many years have passed since the last leap year
        if ( (jump - N) < 6 )
            N = N - jump + ((jump + 4)/33 * 33);
        leap = (((N+1) % 33)-1) % 4;
        if (leap == -1)
            leap = 4;
        if (leap==4 || leap==0)
            return true;
        else
            return false;

    }



    /**
     * IranianDateToJDN:
     * Converts a date of the Iranian calendar to the Julian Day Number. It first
     * invokes the 'IranianCalender' private method to convert the Iranian date to
     * Gregorian date and then returns the Julian Day Number based on the Gregorian
     * date. The Iranian date is obtained from 'irYear'(1-3100),'irMonth'(1-12) and
     * 'irDay'(1-29/31).
     * @return long (Julian Day Number)
     */
    private int IranianDateToJDN()
    {
        IranianCalendar();
        return (gregorianDateToJDN(gYear,3,march)+ (irMonth-1) * 31 - irMonth/7 * (irMonth-7) + irDay -1);
    }

    /**
     * JDNToIranian:
     * Converts the current value of 'JDN' Julian Day Number to a date in the
     * Iranian calendar. The caller should make sure that the current value of
     * 'JDN' is set correctly. This method first converts the JDN to Gregorian
     * calendar and then to Iranian calendar.
     */
    private void JDNToIranian()
    {
        JDNToGregorian();
        irYear = gYear - 621;
        IranianCalendar(); // This invocation will update 'leap' and 'march'
        int JDN1F = gregorianDateToJDN(gYear,3,march);
        int k = JDN - JDN1F;
        if (k >= 0)
        {
            if (k <= 185)
            {
                irMonth = 1 + k/31;
                irDay = (k % 31) + 1;
                return;
            }
            else
                k -= 186;
        }
        else
        {
            irYear--;
            k += 179;
            if (leap == 1)
                k++;
        }
        irMonth = 7 + k/30;
        irDay = (k % 30) + 1;
    }


    /**
     * julianDateToJDN:
     * Calculates the julian day number (JDN) from Julian calendar dates. This
     * integer number corresponds to the noon of the date (i.e. 12 hours of
     * Universal Time). This method was tested to be good (valid) since 1 March,
     * -100100 (of both calendars) up to a few millions (10^6) years into the
     * future. The algorithm is based on D.A.Hatcher, Q.Jl.R.Astron.Soc. 25(1984),
     * 53-55 slightly modified by K.M. Borkowski, Post.Astron. 25(1987), 275-279.
     * @param year int
     * @param month int
     * @param day int
     * @return int
     */
    private int julianDateToJDN(int year, int month, int day)
    {
        return (year + (month - 8) / 6 + 100100) * 1461/4 + (153 * ((month+9) % 12) + 2)/5 + day - 34840408;
    }

    /**
     * JDNToJulian:
     * Calculates Julian calendar dates from the julian day number (JDN) for the
     * period since JDN=-34839655 (i.e. the year -100100 of both calendars) to
     * some millions (10^6) years ahead of the present. The algorithm is based on
     * D.A. Hatcher, Q.Jl.R.Astron.Soc. 25(1984), 53-55 slightly modified by K.M.
     * Borkowski, Post.Astron. 25(1987), 275-279).
     */
    private void JDNToJulian()
    {
        int j= 4 * JDN + 139361631;
        int i= ((j % 1461)/4) * 5 + 308;
        juDay = (i % 153) / 5 + 1;
        juMonth = ((i/153) % 12) + 1;
        juYear = j/1461 - 100100 + (8-juMonth)/6;
    }

    /**
     * gergorianDateToJDN:
     * Calculates the julian day number (JDN) from Gregorian calendar dates. This
     * integer number corresponds to the noon of the date (i.e. 12 hours of
     * Universal Time). This method was tested to be good (valid) since 1 March,
     * -100100 (of both calendars) up to a few millions (10^6) years into the
     * future. The algorithm is based on D.A.Hatcher, Q.Jl.R.Astron.Soc. 25(1984),
     * 53-55 slightly modified by K.M. Borkowski, Post.Astron. 25(1987), 275-279.
     * @param year int
     * @param month int
     * @param day int
     * @return int
     */
    private int gregorianDateToJDN(int year, int month, int day)
    {
        int jdn = (year + (month - 8) / 6 + 100100) * 1461/4 + (153 * ((month+9) % 12) + 2)/5 + day - 34840408;
        jdn = jdn - (year + 100100+(month-8)/6)/100*3/4+752;
        return (jdn);
    }
    /**
     * JDNToGregorian:
     * Calculates Gregorian calendar dates from the julian day number (JDN) for
     * the period since JDN=-34839655 (i.e. the year -100100 of both calendars) to
     * some millions (10^6) years ahead of the present. The algorithm is based on
     * D.A. Hatcher, Q.Jl.R.Astron.Soc. 25(1984), 53-55 slightly modified by K.M.
     * Borkowski, Post.Astron. 25(1987), 275-279).
     */
    private void JDNToGregorian()
    {
        int j= 4 * JDN + 139361631;
        j = j + (((((4* JDN +183187720)/146097)*3)/4)*4-3908);
        int i= ((j % 1461)/4) * 5 + 308;
        gDay = (i % 153) / 5 + 1;
        gMonth = ((i/153) % 12) + 1;
        gYear = j/1461 - 100100 + (8-gMonth)/6;
    }


    private int irYear; // Year part of a Iranian date
    private int irMonth; // Month part of a Iranian date
    private int irDay; // Day part of a Iranian date
    private int gYear; // Year part of a Gregorian date
    private int gMonth; // Month part of a Gregorian date
    private int gDay; // Day part of a Gregorian date
    private int juYear; // Year part of a Julian date
    private int juMonth; // Month part of a Julian date
    private int juDay; // Day part of a Julian date
    private int leap; // Number of years since the last leap year (0 to 4)
    private int JDN; // Julian Day Number
    private int march; // The march day of Farvardin the first (First day of jaYear)
} // End of Class 'JavaSource_Calendar

You can easily set the Gregorian Day, Month and Year, then call "getIranianDate()" method to get the date in string format, just like the sample code below:

MyUtil.CalendarTool ct = new CalendarTool(2012,10,10);
System.out.println(ct.getIranianDate());

I hope it helps.

Use IBM's International Components for Unicode (icu4j). It is part of Unicode Consortium, is extremely reliable and can be used in any java project (Java EE, Java SE, Android, etc). Use it with Gradle, Maven or simply by downloading the jar.

TL;DR

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Date;
import com.ibm.icu.text.DateFormat;
import com.ibm.icu.text.SimpleDateFormat;
import com.ibm.icu.util.Calendar;
import com.ibm.icu.util.ULocale;

public class DateTimeUtils {
    public static final ULocale PERSIAN_LOCALE = new ULocale("fa_IR@calendar=persian");
    public static final ULocale PERSIAN_EN_LOCALE = new ULocale("en@calendar=persian");
    public static final ZoneId IRAN_ZONE_ID = ZoneId.of("Asia/Tehran");

    public static Calendar fromDateToPersianCalendar(Date date) {
        Calendar persianCalendar = Calendar.getInstance(PERSIAN_LOCALE);
        persianCalendar.clear();
        persianCalendar.setTime(date);
        return persianCalendar;
    }

    /**
     * @param date
     * @param field example: Calendar.YEAR, Calendar.MONTH, Calendar.DAY_OF_MONTH, etc
     */
    public static int fromDateToPersianCalendarField(Date date, int field) {
        return fromDateToPersianCalendar(date).get(field);
    }

    public static String fromDateToPersianString(Date date) {
        DateFormat df = DateFormat.getDateInstance(DateFormat.FULL, PERSIAN_LOCALE);
        return df.format(date);
    }

    public static String fromDateToPersianString(Date date, String pattern) {
        return new SimpleDateFormat(pattern, PERSIAN_LOCALE).format(date);
    }

    public static String fromDateToPersianString(Date date, String pattern, ULocale locale) {
        return new SimpleDateFormat(pattern, locale).format(date);
    }

    /**
     * @param month is zero based. (e.g. Farvardin = 0, Ordibehesht = 1, etc.)
     */
    public static Date fromPersianDateToDate(int year, int month, int day, int hour, int minutes, int seconds) {
        return new Date(fromPersianDate(year, month, day, hour, minutes, seconds));
    }

    /**
     * @param month is zero based. (e.g. Farvardin = 0, Ordibehesht = 1, etc.)
     */    
    public static String fromPersianDateToPersianString(int year, int month, int day, int hour, int minutes, int seconds) {
        return fromDateToPersianString(fromPersianDateToDate(year, month, day, hour, minutes, seconds));
    }

    /**
     * @param month is zero based. (e.g. Farvardin = 0, Ordibehesht = 1, etc.)
     */      
    public static LocalDateTime fromPersianDateToLocalDateTime(int year, int month, int day, int hour, int minutes, int seconds) {
        return fromPersianDateToZonedDateTime(year, month, day, hour, minutes, seconds).toLocalDateTime();
    }

    /**
     * @param month is zero based. (e.g. Farvardin = 0, Ordibehesht = 1, etc.)
     */  
    public static ZonedDateTime fromPersianDateToZonedDateTime(int year, int month, int day, int hour, int minutes, int seconds) {
        return toZonedDateTime(fromPersianDate(year, month, day, hour, minutes, seconds));
    }

    /**
     * @param month is zero based. (e.g. Farvardin = 0, Ordibehesht = 1, etc.)
     */  
    public static long fromPersianDate(int year, int month, int day, int hour, int minutes, int seconds) {
        Calendar persianCalendar = Calendar.getInstance(PERSIAN_LOCALE);
        persianCalendar.clear();
        persianCalendar.set(year, month, day, hour, minutes, seconds);
        return persianCalendar.getTimeInMillis();
    }

    public static ZonedDateTime toZonedDateTime(Long epochMilli) {
        if(epochMilli == null) return null;
        return Instant.ofEpochMilli(epochMilli).atZone(IRAN_ZONE_ID);
    }
}

Usage:

import java.time.LocalDateTime;
import java.time.ZonedDateTime;
import java.util.Date;
import com.ibm.icu.util.Calendar;

public class DateTimeUtilsTest {
    public static void main(String[] args) {
        System.out.println("Java 7 and before:");
        Date date = new Date(1467262800000L);
        System.out.println("Converting Gregorian date to Persian:");
        Calendar persianCalendar = DateTimeUtils.fromDateToPersianCalendar(date);
        System.out.println(persianCalendar.get(Calendar.YEAR));
        System.out.println(persianCalendar.get(Calendar.MONTH));
        System.out.println(persianCalendar.get(Calendar.DAY_OF_MONTH));
        System.out.println(DateTimeUtils.fromDateToPersianString(persianCalendar.getTime()));
        
        System.out.println("\nAdding 1 month and 5 days:");
        persianCalendar.add(Calendar.MONTH, 1); // add a month
        persianCalendar.add(Calendar.DAY_OF_MONTH, 5); // add 5 days
        System.out.println(persianCalendar.get(Calendar.YEAR));
        System.out.println(persianCalendar.get(Calendar.MONTH));
        System.out.println(persianCalendar.get(Calendar.DAY_OF_MONTH));
        System.out.println(DateTimeUtils.fromDateToPersianString(persianCalendar.getTime()));
        
        System.out.println("\nConverting Persian date to Gregorian:");
        Date gregorianDate = DateTimeUtils.fromPersianDateToDate(1395, 3, 10, 9, 30, 0);
        System.out.println(gregorianDate);
        System.out.println(DateTimeUtils.fromDateToPersianString(gregorianDate)); // to Persian string
        System.out.println(DateTimeUtils.fromDateToPersianString(gregorianDate, "dd/MM/yy - H:mm:dd")); // to Persian string with custom format
        System.out.println(DateTimeUtils.fromDateToPersianString(gregorianDate, "dd/MM/yy - H:mm:dd" , DateTimeUtils.PERSIAN_EN_LOCALE)); // to Persian string with custom format and Latin characters

        System.out.println("\n"+"Java 8 onward:");
        ZonedDateTime gregorianZonedDateTime = DateTimeUtils.fromPersianDateToZonedDateTime(1395, 3, 10, 9, 30, 0);
        System.out.println(gregorianZonedDateTime);
        LocalDateTime gregorianLocalDateTime = DateTimeUtils.fromPersianDateToLocalDateTime(1395, 3, 10, 9, 30, 0);
        System.out.println(gregorianLocalDateTime);
    }
}

Output:

Java 7 and before:
Converting Gregorian date to Persian:
1395
3
10
۱۳۹۵ تیر ۱۰, پنجشنبه

Adding 1 month and 5 days:
1395
4
15
۱۳۹۵ مرداد ۱۵, جمعه

Converting Persian date to Gregorian:
Thu Jun 30 09:30:00 IRDT 2016
۱۳۹۵ تیر ۱۰, پنجشنبه
۱۰/۰۴/۹۵ - ۹:۳۰:۱۰
10/04/95 - 9:30:10

Java 8 onward:
2016-06-30T09:30+04:30[Asia/Tehran]
2016-06-30T09:30

More detailed:

Java 7 and before:

You can expect all of functionalities of java.util.Calendar in addition to some other ones:

import com.ibm.icu.util.Calendar;
import com.ibm.icu.util.ULocale;

...

ULocale locale = new ULocale("fa_IR@calendar=persian");
Calendar persianCalendar = Calendar.getInstance(locale);
persianCalendar.clear();
persianCalendar.set(1395, 3, 10); // Tir(4th month) 10th 1395 equivalent to June 30th 2016 

java.util.Date gregorianDate = persianCalendar.getTime();
System.out.println(gregorianDate); // Thu Jun 30 00:00:00 IDT 2016

// Gregorian to Persian
java.util.Calendar gregorianCal = java.util.GregorianCalendar.getInstance();
gregorianCal.set(2016, java.util.Calendar.JUNE, 30);

persianCalendar.setTime(gregorianCal.getTime());
System.out.println(persianCalendar.get(Calendar.YEAR));         // 1395
System.out.println(persianCalendar.get(Calendar.MONTH));        // 3
System.out.println(persianCalendar.get(Calendar.DAY_OF_MONTH)); // 10

WARNING: Note that month field is zero based in Java calendar so by calendar.set(1395, 3, 10) calendar will represent 4th month of 1395, not 3rd!

If you need text outputs in persian:

import com.ibm.icu.text.DateFormat;
import com.ibm.icu.text.SimpleDateFormat;

...

// full date output in persian
DateFormat df = DateFormat.getDateInstance(DateFormat.FULL, locale);
System.out.println(df.format(persianCalendar.getTime()));

// year output in persian
SimpleDateFormat sdf1 = new SimpleDateFormat(SimpleDateFormat.YEAR, locale);
System.out.println(sdf1.format(persianCalendar.getTime()));

// month name output in persian
SimpleDateFormat sdf2 = new SimpleDateFormat(SimpleDateFormat.MONTH, locale);
System.out.println(sdf2.format(persianCalendar.getTime()));

// weekday name output in persian
SimpleDateFormat sdf3 = new SimpleDateFormat(SimpleDateFormat.WEEKDAY, locale);
System.out.println(sdf3.format(persianCalendar.getTime()));

// full date output in YY/MM/dd form
SimpleDateFormat sdf4 = new SimpleDateFormat("YY/MM/dd", locale);
System.out.println(sdf4.format(persianCalendar.getTime()));

Output:

ه‍.ش. ۱۳۹۵ تیر ۱۰, پنجشنبه  
۱۳۹۵  
تیر  
پنجشنبه
۹۵/۰۴/۱۰

If you need output to be in english, change new ULocale("fa_IR@calendar=persian") to new ULocale("en@calendar=persian").

Output:

AP 1395 Tir 10, Thu
1395
Tir
Thu
95/04/10

Other nice things:

// Get number of days in month
System.out.println(persianCalendar.getActualMaximum(Calendar.DAY_OF_MONTH)); // 31

// Get first day of week
System.out.println(persianCalendar.getFirstDayOfWeek()); // 7 (Saturday according to docs)

// Add some amount of time
persianCalendar.add(Calendar.MONTH, 2);
System.out.println(persianCalendar.get(Calendar.YEAR));         //1395
System.out.println(persianCalendar.get(Calendar.MONTH));        // 5
System.out.println(persianCalendar.get(Calendar.DAY_OF_MONTH)); // 10

For other functionalities see icu4j demos, specially:

• demo of various calendar fields
• list of Tuesdays and Thursdays of current year
• demo of converting number to text representation (use fa_IR for locale)

Also see Calendar and PersianCalendar API.

Java 8 onward:

In order to use java.time classes like ZonedDateTime or LocalDateTime, you could simply use this methods to convert a persian date to preferred classes:

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import com.ibm.icu.util.Calendar;
import com.ibm.icu.util.ULocale;

...

public static LocalDateTime fromPersianDateToLocalDateTime(int year, int month, int day, int hour, int minutes, int seconds) {
    return fromPersianDateToZonedDateTime(year, month, day, hour, minutes, seconds).toLocalDateTime();
}

public static ZonedDateTime fromPersianDateToZonedDateTime(int year, int month, int day, int hour, int minutes, int seconds) {
    return toZonedDateTime(fromPersianDate(year, month, day, hour, minutes, seconds));
}

public static long fromPersianDate(int year, int month, int day, int hour, int minutes, int seconds) {
    Calendar persianCalendar = Calendar.getInstance(new ULocale("fa_IR@calendar=persian"));
    persianCalendar.clear();
    persianCalendar.set(year, month, day, hour, minutes, seconds);
    return persianCalendar.getTimeInMillis();
}

public static ZonedDateTime toZonedDateTime(Long epochMilli) {
    if(epochMilli == null) return null;
    return Instant.ofEpochMilli(epochMilli).atZone(ZoneId.of("Asia/Tehran"));
}

Remarks About Jar Size

If you're concerned about icu4j's jar size , then you may rebuild it and just use the Calendar module (2,176KB). More Info: ver. 57 or earlier , ver. 58 or later using ICU Data Build Tool.

this method is very exact and simply also support leap years

Explain:

step 1: time today is contain current time

step 2: create two array for gregorian and jalali day in months(g_days_in_month&j_days_in_month)

step 3: create variable for retention difference time between calendars (gy,gm,gd) and variable g_day_no for days of years.

step 4: insert day of month and collect with days.

step 5: convert days of years to jalili years (jy)

at the end : set jalali month from day number, set jalali day from jalali day of month array.

good luck.

    Time today = new Time(Time.getCurrentTimezone());
    today.setToNow();
    int Day = (today.monthDay);             // Day of the month (0-31)
    int Month = (today.month);              // Month (0-11)
    int Year = (today.year);                // Year

    String persianDate = GregorianToJalali(Year, Month+1, Day);

  private String GregorianToJalali(int g_y, int g_m, int g_d)
{

  int[] g_days_in_month = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  int[] j_days_in_month = {31, 31, 31, 31, 31, 31, 30, 30, 30, 30, 30, 29};

    int gy = g_y-1600;
    int gm = g_m-1;
    int gd = g_d-1;

        int g_day_no = 365*gy+div(gy+3,4)-div(gy+99,100)+div(gy+399,400);

        for (int i=0; i < gm; ++i)
          g_day_no += g_days_in_month[i];
        if (gm>1 && ((gy%4==0 && gy%100!=0) || (gy%400==0)))
         // leap and after Feb 
          g_day_no++;
        g_day_no += gd;

       int j_day_no = g_day_no-79;

        int j_np = div(j_day_no, 12053); //12053 = 365*33 + 32/4 
        j_day_no = j_day_no % 12053;

        int jy = 979+33*j_np+4*div(j_day_no,1461); // 1461 = 365*4 + 4/4 

        j_day_no %= 1461;

        if (j_day_no >= 366) {
          jy += div(j_day_no-1, 365);
          j_day_no = (j_day_no-1)%365;
        }

        int j;
        for (j=0; j < 11 && j_day_no >= j_days_in_month[j]; ++j)
          j_day_no -= j_days_in_month[j];
       int jm = j+1;
       int jd = j_day_no+1;


        String Result= jy+"/"+jm+"/"+jd;

        return (Result);
     }  


  private int div(float a, float b)
  {  
      return (int)(a/b); 
  }

The newest version v3.10-2015g of my library Time4A (an Android adaptation of Time4J) contains support for the Jalali calendar. The library deploys the algorithm of Borkowski (valid until gregorian year 2129). Actually about 25 languages are supported for Persian months and eras (including Farsi and Pashto, based on CLDR-28).

Examples of usage:

// current date
PersianCalendar jalali = SystemClock.inLocalView().now(PersianCalendar.axis());
System.out.println(jalali); // AP-1394-08-04

// tomorrow
jalali = jalali.plus(CalendarDays.ONE);
System.out.println(jalali); // AP-1394-08-05

// localized format of tomorrow (English and Farsi)
ChronoFormatter<PersianCalendar> f =
    ChronoFormatter.ofStyle(DisplayMode.FULL, Locale.ENGLISH, PersianCalendar.axis());
Locale farsi = new Locale("fa");
System.out.println(f.format(jalali)); // Tuesday, Aban 5, 1394 AP
System.out.println(f.with(farsi).format(jalali)); // سه‌شنبه, آبان 5, 1394 ه‍.ش.

// shift back to month Farvardin and format the result
jalali = jalali.with(PersianCalendar.MONTH_OF_YEAR, PersianMonth.FARVARDIN);
System.out.println(f.format(jalali)); // Wednesday, Farvardin 5, 1394 AP
System.out.println(f.with(farsi).format(jalali)); // چهارشنبه, فروردین 5, 1394 ه‍.ش.

// conversion to gregorian date
System.out.println(jalali); // AP-1394-01-05
System.out.println(jalali.transform(PlainDate.class)); // 2015-03-25

// create new year in persian calendar and show gregorian counter part
jalali = PersianCalendar.of(1394, PersianMonth.FARVARDIN, 1);
System.out.println(jalali.transform(PlainDate.class)); // 2015-03-21

// create new year in gregorian calendar and show persian counter part
PlainDate gregorianDate = PlainDate.of(2015, Month.JANUARY, 1);
System.out.println(gregorianDate.transform(PersianCalendar.class)); // AP-1393-10-11

// delta between gregorian new year and persian new year
System.out.println(CalendarDays.between(gregorianDate, jalali).getAmount()); // 79

Interoperability with java.util.Date on Android

Since Time4A manages its own set of immutable types and is not based on the primary temporal type of Android, I show following bridge:

// Time4A => Android
PlainDate gdate = jalali.transform(PlainDate.class);
Moment m1 = gdate.atStartOfDay().inTimezone(ASIA.TEHRAN);
java.util.Date jud = TemporalType.JAVA_UTIL_DATE.from(m1);

// Android => Time4A
java.util.Date input = new java.util.Date();
Moment m2 = TemporalType.JAVA_UTIL_DATE.translate(input);
jalali = m2.toZonalTimestamp(ASIA.TEHRAN).toDate().transform(PersianCalendar.class);

Try this

import java.util.Calendar;
import java.util.Date;
public class PersianCalendar {

String[] weekDayNames = {
        "شنبه","یکشنبه","دوشنبه",
        "سه شنبه", "چهارشنبه",
        "پنج شنبه", "جمعه"
};
String[] monthNames ={
        "فروردین","اردیبهشت","خرداد","تیر", "مرداد","شهریور",
         "مهر", "آبان", "آذر","دی", "بهمن","اسفند"
};   
String strWeekDay = "";
String strMonth = "";    
int day;
int month;
int year;    
int ld;     
Calendar calendar = Calendar.getInstance();      
int gregorianYear =calendar.get(Calendar.YEAR);
int gregorianMonth = calendar.get(Calendar.MONTH)+1;
int gregorianDate = calendar.get(Calendar.DATE);
int WeekDay = calendar.get(Calendar.DAY_OF_WEEK);

int[] buf1 = {0,31,59,90,120,151,181,212,243,273,304,334};
int[] buf2 = {0,31,60, 91,121,152,182, 213, 244, 274,305,335};

public PersianCalendar(){
    Date gregorianDate = new Date();
    calendar.setTime(gregorianDate);
    toPersian(gregorianDate);
}

public PersianCalendar(Date gregorianDate){
    calendar.setTime(gregorianDate);
    toPersian(gregorianDate);
}    

private void toPersian(Date gregorianDate) 
{
    if ((gregorianYear % 4) != 0) 
        func1();
    else 
        func2();
    strMonth = monthNames[month-1];
    strWeekDay = weekDayNames[WeekDay];
}

private void func1()
{
    day = buf1[gregorianMonth - 1] + gregorianDate;
    if (day > 79){
        day = day - 79;
        if (day <= 186) {               
            int day2 = day;
            month = (day2 / 31) + 1;
            day = (day2 % 31);
            if(day2 % 31 == 0){
                 month--;
                 day = 31;
            }                
            year = gregorianYear - 621;
        } 
        else {
            int day2 = day - 186;
            month = (day2 / 30) + 7;
            day = (day2 % 30);
            if(day2 % 30 == 0){
                month = (day2 / 30) + 6;
                day = 30;
            }
            year = gregorianYear - 621;
        }
    } 
    else{            
        ld = gregorianYear > 1996 && gregorianYear % 4 == 1 ? 11 : 10 ;            
        int day2 = day + ld;
        month = (day2 / 30) + 10;
        day = (day2 % 30);            
        if(day2 % 30 == 0)            {
            month--;
            day = 30;
        }
        year = gregorianYear - 622;
    }
}

private void func2()
{
    day = buf2[gregorianMonth - 1] + gregorianDate;     
    ld = gregorianYear >= 1996 ? 79 : 80 ;        
    if (day > ld) {
        day = day - ld;
        if (day <= 186) {
            int day2 = day;
            month = (day2 / 31) + 1;
            day = (day2 % 31);
            if(day2 % 31 == 0){
                month--;
                day = 31;
            }
            year = gregorianYear - 621;
        } else {
            int day2 = day - 186; 
            month = (day2 / 30) + 7;
            day = (day2 % 30);
            if(day2 % 30 == 0 ){
                month--;
                day = 30;
            }
            year = gregorianYear - 621;
        }
    }
    else {
        int day2 = day + 10;
        month = (day2 / 30) + 10;
        day = (day2 % 30);
        if(day2 % 30==0){
            month--;
            day = 30;
        }
        year = gregorianYear - 622;
    }
  }
}

create instance

PersianCalendar sc = new PersianCalendar();            
String s= sc.strWeekDay  + " " +sc.day  + " " + 
     sc.strMonth + " " + sc.year;
System.out.print(s);
//setTitle(s);

There is persianutils project which includes a bi-directional DateConverter; Gregorian <-> Persian (Jalali). It is written in Scala, so I suppose using it in a Java project would be quite easy.

The algorithm used is valid for Gregorian years up to ~3790 and Persian years up to ~3170.

DISCLAIMER: I am the author of PersianUtils

You may use this stable and tested library with a formatter class, Roozh for Java. It's not deprecated and always getting updated with cool features which Persian date time needs.

Create the calculateJalaliDate as function like so; and then return the Jalali date in String

public String calculateJalaliDate(){

    Calendar c = Calendar.getInstance();
    String jalaliDate,JalaliMonth;
    int jalaliYear,jalaliMonth,calculateMonth,jalaliDay=0,allDays=0;
    int day=c.get(Calendar.DAY_OF_MONTH);
    int month=c.get(Calendar.MONTH)+1;
    int year=c.get(Calendar.YEAR);

    switch (month){
        case 1: allDays=year*365+31+day;break;
        case 2: allDays=year*365+(31+28)+day;break;
        case 3: allDays=year*365+(31+28+31)+day;break;
        case 4: allDays=year*365+(31+28+31+30)+day;break;
        case 5: allDays=year*365+(31+28+31+30+31)+day;break;
        case 6: allDays=year*365+(31+28+31+30+31+30)+day;break;
        case 7: allDays=year*365+(31+28+31+30+31+30+31)+day;break;
        case 8: allDays=year*365+(31+28+31+30+31+30+31+31)+day;break;
        case 9: allDays=year*365+(31+28+31+30+31+30+31+31+30)+day;break;
        case 10: allDays=year*365+(31+28+31+30+31+30+31+31+30+31)+day;break;
        case 11: allDays=year*365+(31+28+31+30+31+30+31+31+30+31+30)+day;break;
        case 12: allDays=year*365+(31+28+31+30+31+30+31+31+30+31+30+31)+day;break;
    }

    //226899
    jalaliYear=( allDays - 227139 )/365+1;
    calculateMonth=( allDays - 227139 )%365;
    if(calculateMonth<32)jalaliMonth=1;
    else if((calculateMonth-31)<32){jalaliMonth=2;jalaliDay=calculateMonth-31;}
    else if((calculateMonth-62)<32){jalaliMonth=3;jalaliDay=calculateMonth-62;}
    else if((calculateMonth-93)<32){jalaliMonth=4;jalaliDay=calculateMonth-93;}
    else if((calculateMonth-124)<32){jalaliMonth=5;jalaliDay=calculateMonth-124;}
    else if((calculateMonth-155)<32){jalaliMonth=6;jalaliDay=calculateMonth-155;}
    else if((calculateMonth-186)<31){jalaliMonth=7;jalaliDay=calculateMonth-186;}
    else if((calculateMonth-216)<31){jalaliMonth=8;jalaliDay=calculateMonth-216;}
    else if((calculateMonth-246)<31){jalaliMonth=9;jalaliDay=calculateMonth-246;}
    else if((calculateMonth-276)<31){jalaliMonth=10;jalaliDay=calculateMonth-276;}
    else if((calculateMonth-306)<31){jalaliMonth=11;jalaliDay=calculateMonth-306;}
    else {
        jalaliMonth=12;
        if((jalaliYear%4)==0)jalaliDay=calculateMonth-336;
        else jalaliDay=calculateMonth-335;
    }



    /*switch (jalaliMonth){
        case 1:JalaliMonth="فروردین"; break;
        case 2:JalaliMonth="اردیبهشت"; break;
        case 3:JalaliMonth="خرداد"; break;
        case 4:JalaliMonth="تیر"; break;
        case 5:JalaliMonth="مرداد"; break;
        case 6:JalaliMonth="شهریور"; break;
        case 7:JalaliMonth="مهر"; break;
        case 8:JalaliMonth="آبان"; break;
        case 9:JalaliMonth="آذر"; break;
        case 10:JalaliMonth="دی"; break;
        case 11:JalaliMonth="بهمن"; break;
        case 12:JalaliMonth="اسفند"; break;
    }*/


    jalaliDate=String.valueOf(jalaliYear)+"/"+String.valueOf(jalaliMonth)+"/"+String.valueOf(jalaliDay);
    return jalaliDate;
}

I have developed Android Shamsi datepicker widget with hijri - gerogian- shamsi event view: https://github.com/irshst/ir.shes.calendar

Beside Time4A, icu4j, which are too heavy libraries, I written a class to handle Persian calendar accurately and you can find it here: https://github.com/hadilq/java-persian-calendar/blob/master/persian/src/main/java/ir/hadilq/PersianCalendar.java

As you can find it in its tests, this class supports from year 3000 before hijra to 3000 after hijra.