Use this calculator to convert dates between the Gregorian (Western) calendar and the Hijri (Islamic) calendar. The Hijri calendar is a lunar calendar, meaning its dates drift relative to the solar Gregorian calendar.
Gregorian Date
Hijri Date
Understanding the Arabic (Hijri) Calendar
The Arabic calendar, also known as the Hijri calendar or Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used by Muslims worldwide to determine the proper days of Islamic holidays and rituals, such as the fasting month of Ramadan, the pilgrimage to Mecca (Hajj), and the celebration of Eid al-Fitr and Eid al-Adha.
Origin of the Hijri Calendar
The calendar's epoch (starting point) is the Hijra, the migration of Prophet Muhammad and his followers from Mecca to Medina in 622 CE (Common Era). The first day of the Hijri calendar, 1 Muharram 1 AH (Anno Hegirae), corresponds to approximately July 19, 622 CE in the proleptic Gregorian calendar (or July 16, 622 CE in the Julian calendar).
Lunar vs. Solar Calendars
Unlike the Gregorian calendar, which is a solar calendar based on the Earth's orbit around the sun (approximately 365.25 days), the Hijri calendar is purely lunar. Each month begins with the sighting of the crescent moon (hilal). Because a lunar year is about 10 to 11 days shorter than a solar year, Hijri dates gradually shift relative to Gregorian dates. This means that Islamic holidays occur in different seasons over a cycle of about 33 solar years.
Hijri Months
Muharram (مُحَرَّم)
Safar (صَفَر)
Rabi' al-Awwal (رَبِيع ٱلْأَوَّل)
Rabi' al-Thani (رَبِيع ٱلْآخِر or رَبِيع ٱلثَّانِي)
Jumada al-Awwal (جُمَادَىٰ ٱلْأُولَىٰ)
Jumada al-Thani (جُمَادَىٰ ٱلْآخِرَة or جُمَادَىٰ ٱلثَّانِيَة)
Rajab (رَجَب)
Sha'ban (شَعْبَان)
Ramadan (رَمَضَان)
Shawwal (شَوَّال)
Dhu al-Qadah (ذُو ٱلْقَعْدَة)
Dhu al-Hijjah (ذُو ٱلْحِجَّة)
How the Calculator Works
This calculator uses a widely accepted arithmetic algorithm to convert dates between the Gregorian and Hijri calendars. It relies on the concept of the Julian Day Number (JDN), a continuous count of days since a specific historical epoch. By converting both Gregorian and Hijri dates to their corresponding JDN, the calculator can accurately translate between the two systems. It accounts for the varying lengths of months and the occurrence of leap years in both calendars.
Important Note on Accuracy
It's important to note that while this calculator provides a highly accurate conversion based on astronomical calculations, the actual start of Hijri months can sometimes vary by a day or two in different regions due to local moon sighting traditions or different calculation methodologies. This calculator uses a fixed arithmetic calendar, which is consistent but may not always perfectly align with observed dates in all communities.
Examples of Date Conversion
Here are a few examples to illustrate the conversion:
Gregorian to Hijri: If you convert January 1, 2024 CE, you will get approximately 19 Jumada al-Thani 1445 AH.
Hijri to Gregorian: If you convert 1 Ramadan 1445 AH, you will get approximately March 11, 2024 CE.
Historical Date: The Hijra (migration) itself, which marks the beginning of the Hijri calendar, occurred around July 19, 622 CE (Proleptic Gregorian), corresponding to 1 Muharram 1 AH.
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// Global constants for Hijri calendar
// JDN for 1 Muharram 1 AH (approx. July 19, 622 CE Proleptic Gregorian)
var HIJRI_EPOCH_JDN = 1948440;
// Hijri month names
var hijriMonthNames = [
"", // Index 0 unused
"Muharram", "Safar", "Rabi' al-Awwal", "Rabi' al-Thani",
"Jumada al-Awwal", "Jumada al-Thani", "Rajab", "Sha'ban",
"Ramadan", "Shawwal", "Dhu al-Qadah", "Dhu al-Hijjah"
];
// Gregorian month names
var gregorianMonthNames = [
"", "January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December"
];
// Day names (Sunday is index 0)
var dayNames = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
// Number of days in Hijri months (common year)
var daysInHijriMonthCommon = [0, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29]; // Dhu al-Hijjah (month 12) is 29 in common year
// Function to check if a Hijri year is a leap year
// Hijri leap years occur in a 30-year cycle: years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, 29
function isHijriLeapYear(year) {
return (year * 11 + 14) % 30 < 11;
}
// — Gregorian to Julian Day Number (JDN) —
// This function converts a Gregorian date to a Julian Day Number (proleptic Gregorian calendar).
function gregorianToJDN(year, month, day) {
var a = Math.floor((14 – month) / 12);
var y = year + 4800 – a;
var m = month + 12 * a – 3;
return day + Math.floor((153 * m + 2) / 5) + 365 * y + Math.floor(y / 4) – Math.floor(y / 100) + Math.floor(y / 400) – 32045;
}
// — JDN to Gregorian Date —
// This function converts a Julian Day Number to a Gregorian date.
function JDNToGregorian(jdn) {
var l = jdn + 68569;
var n = Math.floor((4 * l) / 146097);
l = l – Math.floor((146097 * n + 3) / 4);
var i = Math.floor((4000 * (l + 1)) / 1461001);
l = l – Math.floor((1461 * i) / 4) + 31;
var j = Math.floor((80 * l) / 2447);
var day = l – Math.floor((2447 * j) / 80);
l = Math.floor(j / 11);
var month = j + 2 – 12 * l;
var year = 100 * (n – 49) + i + l;
return { year: year, month: month, day: day };
}
// — Hijri to Julian Day Number (JDN) —
// This uses a common arithmetic approximation for the tabular Islamic calendar.
function hijriToJDN(hYear, hMonth, hDay) {
var jd = hDay + Math.ceil(29.5 * (hMonth – 1)) + (hYear – 1) * 354 + Math.floor((3 + 11 * (hYear – 1)) / 30) + HIJRI_EPOCH_JDN – 1;
return jd;
}
// — JDN to Hijri Date —
// This function converts a Julian Day Number to a Hijri date.
function JDNToHijri(jdn) {
var year, month, day;
var jd = jdn – HIJRI_EPOCH_JDN;
// Estimate year using an approximation
year = Math.floor((jd * 30 + 10646) / 10631);
// Refine year by checking the JDN of the start of the estimated Hijri year
// The hijriToJDN function is used here to get the JDN of the start of a Hijri year.
// We subtract HIJRI_EPOCH_JDN to get days relative to the epoch, matching 'jd'.
while (jd = hijriToJDN(year + 1, 1, 1) – HIJRI_EPOCH_JDN) {
year++;
}
// Calculate days into the current Hijri year
var daysIntoYear = jd – (hijriToJDN(year, 1, 1) – HIJRI_EPOCH_JDN);
// Determine month and day within the year
var currentHijriMonthLengths = daysInHijriMonthCommon.slice(); // Copy default lengths
if (isHijriLeapYear(year)) {
currentHijriMonthLengths[12] = 30; // Dhu al-Hijjah (month 12) is 30 in leap year
}
month = 1;
while (daysIntoYear >= currentHijriMonthLengths[month]) {
daysIntoYear -= currentHijriMonthLengths[month];
month++;
}
day = daysIntoYear + 1;
return { year: year, month: month, day: day };
}
// — Input Field Toggling —
function toggleInputFields() {
var gregorianRadio = document.getElementById("conversionTypeGregorian");
var gregorianInputs = document.getElementById("gregorianInputs");
var hijriInputs = document.getElementById("hijriInputs");
if (gregorianRadio.checked) {
gregorianInputs.style.display = "block";
hijriInputs.style.display = "none";
} else {
gregorianInputs.style.display = "none";
hijriInputs.style.display = "block";
}
document.getElementById("result").innerHTML = ""; // Clear previous result
}
// — Main Calculation Function —
function calculateDate() {
var conversionType = document.querySelector('input[name="conversionType"]:checked').value;
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous result
var inputDay, inputMonth, inputYear;
var jdn;
var outputDate;
var outputString = "";
if (conversionType === "gregorianToHijri") {
inputDay = parseInt(document.getElementById("gregDay").value);
inputMonth = parseInt(document.getElementById("gregMonth").value);
inputYear = parseInt(document.getElementById("gregYear").value);
if (isNaN(inputDay) || isNaN(inputMonth) || isNaN(inputYear) || inputDay < 1 || inputMonth 12 || inputYear < 1) {
resultDiv.innerHTML = "Please enter valid Gregorian date (Day, Month, Year).";
return;
}
// Basic Gregorian date validation (e.g., Feb 30)
var tempDate = new Date(inputYear, inputMonth – 1, inputDay);
if (tempDate.getFullYear() !== inputYear || tempDate.getMonth() !== inputMonth – 1 || tempDate.getDate() !== inputDay) {
resultDiv.innerHTML = "Invalid Gregorian date. Please check day and month.";
return;
}
jdn = gregorianToJDN(inputYear, inputMonth, inputDay);
outputDate = JDNToHijri(jdn);
var dayOfWeek = dayNames[(jdn + 1) % 7]; // JDN 0 is Monday, so +1 for Sunday start
outputString = "" + gregorianMonthNames[inputMonth] + " " + inputDay + ", " + inputYear + " CE converts to " + dayOfWeek + ", " + outputDate.day + " " + hijriMonthNames[outputDate.month] + " " + outputDate.year + " AH";
} else { // hijriToGregorian
inputDay = parseInt(document.getElementById("hijriDay").value);
inputMonth = parseInt(document.getElementById("hijriMonth").value);
inputYear = parseInt(document.getElementById("hijriYear").value);
if (isNaN(inputDay) || isNaN(inputMonth) || isNaN(inputYear) || inputDay < 1 || inputMonth 12 || inputYear < 1) {
resultDiv.innerHTML = "Please enter valid Hijri date (Day, Month, Year).";
return;
}
// Basic Hijri date validation
var maxHijriDay = daysInHijriMonthCommon[inputMonth];
if (inputMonth === 12 && isHijriLeapYear(inputYear)) {
maxHijriDay = 30;
}
if (inputDay > maxHijriDay) {
resultDiv.innerHTML = "Invalid Hijri day for the selected month and year.";
return;
}
jdn = hijriToJDN(inputYear, inputMonth, inputDay);
outputDate = JDNToGregorian(jdn);
var dayOfWeek = dayNames[(jdn + 1) % 7]; // JDN 0 is Monday, so +1 for Sunday start
outputString = "" + hijriMonthNames[inputMonth] + " " + inputDay + ", " + inputYear + " AH converts to " + dayOfWeek + ", " + gregorianMonthNames[outputDate.month] + " " + outputDate.day + ", " + outputDate.year + " CE";
}
resultDiv.innerHTML = outputString;
}
// Initialize input fields display on load
window.onload = function() {
toggleInputFields();
};