Kalendar Hijrah Islam | GhazaliTajuddin

Dah lama aku mencari algorithm Hijrah ni.

Kebanyakan kalendar Hijrah ni menggunakan 2 algorithm

Um Al Qura algorithm
Tabular Algorithm

Tapi buat masa ni baru jumpa Um Al Qura algorithm dibuat berdasarkan hasil kerja Robert Harry van Gent work. Beliau menulis algorithm bagi menukankan tarikh gregorian kepada hijriah.

Boleh dapatkan library javascript menukar tarikh daripada Geregorian kepada Hijriah di Github https://github.com/talomaireeni/Umm-Al-Qura-Calendar.

Al-habib.info ada kongsikan calculation yang telah dipermudahkan disini.

function gmod(n,m){
	return ((n%m)+m)%m;
}

function kuwaiticalendar(adjust){
	var today = new Date();
	if(adjust) {
		adjustmili = 1000*60*60*24*adjust; 
		todaymili = today.getTime()+adjustmili;
		today = new Date(todaymili);
	}
	day = today.getDate();
	month = today.getMonth();
	year = today.getFullYear();
	m = month+1;
	y = year;
	if(m<3) {
		y -= 1;
		m += 12;
	}

	a = Math.floor(y/100.);
	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;
		}
	}

	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.);
	}
	bb = jd+b+1524;
	cc = Math.floor((bb-122.1)/365.25);
	dd = Math.floor(365.25*cc);
	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;

	if(adjust) {
		wd = gmod(jd+1-adjust,7)+1;
	} else {
		wd = gmod(jd+1,7)+1;
	}

	iyear = 10631./30.;
	epochastro = 1948084;
	epochcivil = 1948085;

	shift1 = 8.01/60.;
	
	z = jd-epochastro;
	cyc = Math.floor(z/10631.);
	z = z-10631*cyc;
	j = Math.floor((z-shift1)/iyear);
	iy = 30*cyc+j;
	z = z-Math.floor(j*iyear+shift1);
	im = Math.floor((z+28.5001)/29.5);
	if(im==13) im = 12;
	id = z-Math.floor(29.5001*im-29);

	var myRes = new Array(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;
}
function writeIslamicDate(adjustment) {
	var wdNames = new Array("Ahad","Ithnin","Thulatha","Arbaa","Khams","Jumuah","Sabt");
	var iMonthNames = new Array("Muharram","Safar","Rabi'ul Awwal","Rabi'ul Akhir",
	"Jumadal Ula","Jumadal Akhira","Rajab","Sha'ban",
	"Ramadan","Shawwal","Dhul Qa'ada","Dhul Hijja");
	var iDate = kuwaiticalendar(adjustment);
	var outputIslamicDate = wdNames[iDate[4]] + ", " 
	+ iDate[5] + " " + iMonthNames[iDate[6]] + " " + iDate[7] + " AH";
	return outputIslamicDate;
}

Untuk menggunakan script atas seperti berikut

document.write(writeIslamicDate());

Other reference