Enter a Gregorian date below to convert it to its corresponding Hebrew date.
Hebrew Date:
Understanding the Hebrew Calendar
The Hebrew calendar (הלוח העברי, HaLuah HaIvri) is a lunisolar calendar used predominantly for Jewish religious observances. It determines the dates for Jewish holidays, Torah readings, and the Jewish liturgical year. Unlike the Gregorian calendar, which is purely solar, the Hebrew calendar is based on both the cycles of the moon (for months) and the sun (for years).
Lunisolar Nature
Each month of the Hebrew calendar begins with the appearance of the new moon. A standard lunar month is approximately 29.5 days long. To keep the calendar aligned with the solar year and the seasons (which is crucial for agricultural festivals like Passover and Sukkot), an extra month, Adar I, is added seven times in a 19-year cycle. This intercalation ensures that Passover always falls in the spring.
Structure of the Year
A common Hebrew year has 12 months, while a leap year has 13 months. The length of a year can vary: a "deficient" year has 353 days, a "regular" year has 354 days, and a "complete" year has 355 days. In leap years, these lengths become 383, 384, and 385 days, respectively. These variations are due to the flexible lengths of the months Cheshvan and Kislev, which can be 29 or 30 days long, depending on the complex rules of the calendar.
Key Principles and Calculations
The Hebrew calendar's calculations are based on the "Molad" (מוֹלָד), which is the calculated time of the new moon's conjunction. Rosh Hashanah, the Jewish New Year, is determined by the Molad of Tishrei, with several "Dehiyyot" (דְחִיּוֹת, postponements) rules applied to ensure that certain holidays do not fall on specific days of the week, or to prevent the year from being too short or too long. These rules are intricate and have been meticulously calculated for centuries.
Importance in Jewish Life
The Hebrew calendar is central to Jewish life. It dictates the timing of Shabbat, all major and minor holidays (e.g., Rosh Hashanah, Yom Kippur, Passover, Hanukkah), fast days, and even the appropriate times for certain prayers. Understanding the Hebrew date allows individuals to connect with Jewish tradition and observe religious practices correctly.
How This Calculator Works
This calculator takes a standard Gregorian date (day, month, and year) and converts it into its corresponding Hebrew date. It uses a sophisticated algorithm that accounts for the lunisolar cycles, leap years, and the specific rules (Molad and Dehiyyot) that govern the Hebrew calendar. Simply input your desired Gregorian date, and the calculator will provide the equivalent Hebrew day, month, and year.
Examples of Hebrew Date Conversions
Here are a few examples to illustrate how Gregorian dates convert to Hebrew dates:
Gregorian: January 1, 2024
Hebrew: 20 Tevet, 5784
Gregorian: April 23, 2024 (First day of Passover)
Hebrew: 15 Nisan, 5784
Gregorian: October 3, 2024 (Rosh Hashanah)
Hebrew: 1 Tishrei, 5785
Gregorian: December 26, 2024 (First day of Hanukkah)
Hebrew: 25 Kislev, 5785
Gregorian: July 4, 2025
Hebrew: 8 Tammuz, 5785
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// Constants for Hebrew calendar calculations
var HEBREW_EPOCH = 347997; // JDN of 1 Tishrei, 1 (Gregorian Oct 6, 3761 BCE)
var CHALAKIM_PER_HOUR = 1080;
var CHALAKIM_PER_DAY = 24 * CHALAKIM_PER_HOUR; // 25920
var MEAN_LUNAR_MONTH_CHALAKIM = 29 * CHALAKIM_PER_DAY + 12 * CHALAKIM_PER_HOUR + 793; // 765433 parts
// Hebrew month names in calendar year order (starting Tishrei)
var HEBREW_MONTH_NAMES_CALENDAR_ORDER = [
"Tishrei", "Cheshvan", "Kislev", "Tevet", "Shevat",
"Adar", "Nisan", "Iyar", "Sivan", "Tammuz", "Av", "Elul"
];
var HEBREW_MONTH_NAMES_LEAP_CALENDAR_ORDER = [
"Tishrei", "Cheshvan", "Kislev", "Tevet", "Shevat",
"Adar I", "Adar II", "Nisan", "Iyar", "Sivan", "Tammuz", "Av", "Elul"
];
// Julian Day Number (JDN) for Gregorian date
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;
}
// Determine if a Hebrew year is a leap year
function isHebrewLeap(h_year) {
var b = (h_year * 7 + 1);
return (b % 19 = 18) {
new_year_jdn++;
}
// Rule 3: If Molad of a common year falls on a Tuesday after 9 hours and 204 parts
// (Tuesday is day 1 in 0=Mon…6=Sun system)
if (!isHebrewLeap(h_year) && molad_day_of_week === 1 && molad_hour >= 9 && molad_chalakim >= 204) {
new_year_jdn += 2; // Postpone to Thursday
}
// Rule 4: If Molad of a year following a leap year falls on a Monday after 15 hours and 589 parts
// (Monday is day 0 in 0=Mon…6=Sun system)
if (isHebrewLeap(h_year – 1) && molad_day_of_week === 0 && molad_hour >= 15 && molad_chalakim >= 589) {
new_year_jdn++;
}
// Re-check Rule 1 after postponements (this is crucial as postponements can shift the day of week)
// If the new_year_jdn now falls on a Sunday, Wednesday, or Friday, it must be postponed again.
var final_day_of_week = (new_year_jdn – HEBREW_EPOCH) % 7; // Day of week for the calculated Rosh Hashanah (0=Mon)
if (final_day_of_week === 6 || final_day_of_week === 2 || final_day_of_week === 4) {
new_year_jdn++;
}
return new_year_jdn;
}
// Calculate the number of days in a Hebrew year
function hebrewYearLength(h_year) {
var next_year_jdn = hebrewNewYearJDN(h_year + 1);
var current_year_jdn = hebrewNewYearJDN(h_year);
return next_year_jdn – current_year_jdn;
}
// Get the lengths of months for a given Hebrew year, in calendar year order (Tishrei first)
function getHebrewMonthLengths(h_year) {
var is_leap = isHebrewLeap(h_year);
var year_length = hebrewYearLength(h_year);
var cheshvan_len = 29; // Default
var kislev_len = 29; // Default
// Determine Cheshvan and Kislev lengths based on year length
if (is_leap) {
if (year_length === 383) { // Deficient leap year
cheshvan_len = 29;
kislev_len = 29;
} else if (year_length === 384) { // Regular leap year
cheshvan_len = 29;
kislev_len = 30;
} else if (year_length === 385) { // Complete leap year
cheshvan_len = 30;
kislev_len = 30;
}
} else { // Common year
if (year_length === 353) { // Deficient common year
cheshvan_len = 29;
kislev_len = 29;
} else if (year_length === 354) { // Regular common year
cheshvan_len = 29;
kislev_len = 30;
} else if (year_length === 355) { // Complete common year
cheshvan_len = 30;
kislev_len = 30;
}
}
var months = [
30, // Tishrei
cheshvan_len, // Cheshvan
kislev_len, // Kislev
29, // Tevet
30 // Shevat
];
if (is_leap) {
months.push(30); // Adar I
months.push(29); // Adar II
} else {
months.push(29); // Adar (common)
}
months.push(30); // Nisan
months.push(29); // Iyar
months.push(30); // Sivan
months.push(29); // Tammuz
months.push(30); // Av
months.push(29); // Elul
return months;
}
// Convert Julian Day Number to Hebrew Date
function jdnToHebrew(jdn) {
// Approximate Hebrew year
var h_year = Math.floor((jdn – HEBREW_EPOCH) / 365.2425) + 1; // Rough estimate
// Adjust h_year until JDN falls within its range
while (jdn = hebrewNewYearJDN(h_year + 1)) {
h_year++;
}
var days_since_new_year = jdn – hebrewNewYearJDN(h_year);
var month_lengths_in_year = getHebrewMonthLengths(h_year);
var month_index_in_year = 0;
var h_day = 0;
// Iterate through months to find the correct month and day
for (var i = 0; i < month_lengths_in_year.length; i++) {
if (days_since_new_year < month_lengths_in_year[i]) {
month_index_in_year = i;
h_day = days_since_new_year + 1;
break;
}
days_since_new_year -= month_lengths_in_year[i];
}
var current_month_names = isHebrewLeap(h_year) ? HEBREW_MONTH_NAMES_LEAP_CALENDAR_ORDER : HEBREW_MONTH_NAMES_CALENDAR_ORDER;
var h_month_name = current_month_names[month_index_in_year];
return {
day: h_day,
month: h_month_name,
year: h_year
};
}
function calculateHebrewDate() {
var gregorianDay = parseInt(document.getElementById("gregorianDay").value);
var gregorianMonth = parseInt(document.getElementById("gregorianMonth").value);
var gregorianYear = parseInt(document.getElementById("gregorianYear").value);
if (isNaN(gregorianDay) || isNaN(gregorianMonth) || isNaN(gregorianYear) ||
gregorianDay 31 ||
gregorianMonth 12 ||
gregorianYear < 1) {
document.getElementById("result").innerHTML = "Please enter valid Gregorian date values.";
return;
}
// Basic date validation (e.g., Feb 30)
var date = new Date(gregorianYear, gregorianMonth – 1, gregorianDay);
if (date.getFullYear() !== gregorianYear || date.getMonth() !== gregorianMonth – 1 || date.getDate() !== gregorianDay) {
document.getElementById("result").innerHTML = "Invalid Gregorian date. Please check day and month for the given year.";
return;
}
var jdn = gregorianToJDN(gregorianYear, gregorianMonth, gregorianDay);
var hebrewDate = jdnToHebrew(jdn);
document.getElementById("result").innerHTML = hebrewDate.day + " " + hebrewDate.month + ", " + hebrewDate.year;
}
// Initial calculation on page load for default values
window.onload = function() {
calculateHebrewDate();
};