Gregorian-Hijri Dates Converter JAVA

[Ghaith Shamayleh]

import java.util.Calendar;
/**
* Gregorian-Hijri Dates Converter
*
*
* This Code is used to convert Gregorian dates to Hijri Dates
*
*
*/
public class DateHigri {
static double gmod(double n,double m) {
return ((n % m) + m) % m;
}
static double[] kuwaiticalendar(boolean adjust) {
Calendar today = Calendar.getInstance();
int adj=0;
if(adjust){
adj=0;
}else{
adj=1;
}
if (adjust) {
int adjustmili = 1000 * 60 * 60 * 24 * adj;
long todaymili = today.getTimeInMillis() + adjustmili;
today.setTimeInMillis(todaymili);
}
double day = today.get(Calendar.DAY_OF_MONTH);
double month = today.get(Calendar.MONTH);
double year = today.get(Calendar.YEAR);
double m = month + 1;
double y = year;
if (m < 3) {
y -= 1;
m += 12;
}
double a = Math.floor(y / 100.);
double b = 2 - a + Math.floor(a / 4.);
if (y < 1583)
b = 0;
if (y == 1582) {
if (m > 10)
b = -10;
if (m == 10) {
b = 0;
if (day > 4)
b = -10;
}
}
double jd = Math.floor(365.25 * (y + 4716)) + Math.floor(30.6001 * (m + 1)) + day
+ b - 1524;
b = 0;
if (jd > 2299160) {
a = Math.floor((jd - 1867216.25) / 36524.25);
b = 1 + a - Math.floor(a / 4.);
}
double bb = jd + b + 1524;
double cc = Math.floor((bb - 122.1) / 365.25);
double dd = Math.floor(365.25 * cc);
double ee = Math.floor((bb - dd) / 30.6001);
day = (bb - dd) - Math.floor(30.6001 * ee);
month = ee - 1;
if (ee > 13) {
cc += 1;
month = ee - 13;
}
year = cc - 4716;
double wd = gmod(jd + 1, 7) + 1;
double iyear = 10631. / 30.;
double epochastro = 1948084;
double epochcivil = 1948085;
double shift1 = 8.01 / 60.;
double z = jd - epochastro;
double cyc = Math.floor(z / 10631.);
z = z - 10631 * cyc;
double j = Math.floor((z - shift1) / iyear);
double iy = 30 * cyc + j;
z = z - Math.floor(j * iyear + shift1);
double im = Math.floor((z + 28.5001) / 29.5);
if (im == 13)
im = 12;
double id = z - Math.floor(29.5001 * im - 29);
double[] myRes = new double[8];
myRes[0] = day; // calculated day (CE)
myRes[1] = month - 1; // calculated month (CE)
myRes[2] = year; // calculated year (CE)
myRes[3] = jd - 1; // julian day number
myRes[4] = wd - 1; // weekday number
myRes[5] = id; // islamic date
myRes[6] = im - 1; // islamic month
myRes[7] = iy; // islamic year
return myRes;
}
static String writeIslamicDate() {
String[] wdNames = {"Ahad", "Ithnin", "Thulatha", "Arbaa", "Khams",
"Jumuah", "Sabt"};
String[] iMonthNames = {"Muharram", "Safar", "Rabi'ul Awwal",
"Rabi'ul Akhir", "Jumadal Ula", "Jumadal Akhira", "Rajab",
"Sha'ban", "Ramadan", "Shawwal", "Dhul Qa'ada", "Dhul Hijja"};
// This Value is used to give the correct day +- 1 day
boolean dayTest=true;
double[] iDate = kuwaiticalendar(dayTest);
String outputIslamicDate = wdNames[(int) iDate[4]] + ", " + iDate[5] + " "
+ iMonthNames[(int) iDate[6]] + " " + iDate[7] + " AH";
return outputIslamicDate;
}
}

[Joanne Neal]

Did you have a question or are you just sharing your code ?

[Ghaith Shamayleh]

Am just sharing the code

[Jesper de Jong]

Ok, thanks then.

I do have some comments about the code. It contains a lot of "magic" numbers: 365.25, 4716, 30.6001, 1524, 2299160, 1867216.25, 36524.25, 122.1, 10631, 1948084, 1948085, 8.01, 28.5001, 29.5001, ...

What do all those numbers mean? How do you know this code works correctly? For which range of dates does it work correctly?

[Ghaith Shamayleh]

These numbers are used to calculate the Islamic Higri date, you can check if the date returned on the following site if its correct
http://www.islamicity.com/PrayerTimes/defaultHijriConv.asp

[Ulf Dittmer]

365.25 in particular sounds suspicious - does this code handle leap years correctly in the long run?

Maybe you can provide a link to Wikipedia page or something like that where the topic (not necessarily the calculations) are explained.

[Ghaith Shamayleh]

http://en.wikipedia.org/wiki/Islamic_calendar
http://en.wikipedia.org/wiki/Kuwaiti_algorithm

[abu alfouz]

Very useful .. thank you

[Rob Spoor]

 

ghaith shamayleh wrote:These numbers are used to calculate the Islamic Higri date, you can check if the date returned on the following site if its correct
http://www.islamicity.com/PrayerTimes/defaultHijriConv.asp

Then make them constants - private static final fields of the right type (int / double) with a descriptive name.

[Campbell Ritchie]

The duration of a year is not 365.25 days. According to this webpage that is 11min 14 seconds too long. anyway, using floating-point arithmetic is bound to cause imprecisions.

[Jesper de Jong]

 

Campbell Ritchie wrote:The duration of a year is not 365.25 days. According to this webpage that is 11min 14 seconds too long. anyway, using floating-point arithmetic is bound to cause imprecisions.

It's much more complicated than that.

According to Wikipedia, a Julian year is 365.25 days. I guess that the definition on the above website is the length of a Gregorian year (a year according to the usual Gregorial calendar). But there are also other ways to define a year: for example a sidereal year, which is the time it takes the Earth to make exactly one orbit around the Sun, is slightly different (365 days, 6 hours 9 minutes, 9.7676 seconds). And there are other definitions which are again slightly different.

[Ashna Ali]

This code worked for me. But in my country its 25 rajab today and this code shows me 26 rajab. How can i change this please help me. Its so important for me. I have tried to change this by subtracting 1 but then it shows 0 as first day of month.Please help me
Thank you so much for your code.

[Jesper de Jong]

If you are using Java 8 then you do not need this code - the new date and time API in Java 8 already supports the Arabic calendar. You can simply do this:

import java.time.chrono.HijrahDate;
public class PrintToday {
   public static void main(String[] args) {
       HijrahDate today = HijrahDate.now();
       System.out.println(today);
   }
}

[Ashna Ali]

I am using java with android and It does not supports this

[Jesper de Jong]

There is a library named Time4A which can do what you need. It's an advanced date and time library specifically for Android.

See also this post: How to display name Hijri month as a String using Joda-Time?

[sindhu microban]

thanks its work in android studio

[Campbell Ritchie]

SM: welcome to the Ranch