Convert Gregorian dates to Hebrew dates and explore the Jewish calendar system.
Gregorian to Hebrew Date Converter
Enter the date in the Gregorian calendar.
—
Hebrew Year: —
Hebrew Month: —
Hebrew Day: —
This calculator converts a Gregorian date to its corresponding Hebrew date using complex astronomical and calendrical algorithms. It accounts for leap years in both calendars, the start of the Jewish year (Rosh Hashanah), and the lunar cycles.
Hebrew Calendar Overview
Hebrew Month
Gregorian Approximate Start
Days
Notes
Tishrei (תִּשְׁרִי)
September/October
30
Starts the Jewish year (Rosh Hashanah)
Cheshvan (מַרְחֶשְׁוָן)
October/November
29 or 30
Variable length (Mar)
Kislev (כִּסְלו)
November/December
29 or 30
Variable length (Chas)
Tevet (טֵבֵת)
December/January
29
Shevat (שְׁבָט)
January/February
30
Tu BiShvat (New Year for Trees)
Adar I (אֲדָר א')
February/March (Leap Year)
30
Added in leap years
Adar II (אֲדָר ב')
February/March (Leap Year) / March (Common Year)
29
Adar in common years
Nisan (נִיסָן)
March/April
30
Passover
Iyar (אִיָּר)
April/May
29
Lag BaOmer
Sivan (סִיוָן)
May/June
30
Shavuot
Tammuz (תַּמּוּז)
June/July
29
Fast of Tammuz
Av (אָב)
July/August
30
Fast of Tisha B'Av
Elul (אֱלוּל)
August/September
29
Key details about the months of the Hebrew calendar.
Hebrew Calendar Year Comparison
Comparison of Hebrew and Gregorian years over a sample period.
What is a Jewish Calendar Calculator?
A Jewish calendar calculator, also known as a Hebrew calendar converter, is a digital tool designed to accurately translate dates from the Gregorian calendar (the internationally recognized civil calendar) into their corresponding dates on the Hebrew calendar. This is crucial for observing Jewish holidays, lifecycle events, and historical commemorations, which are all determined by the Hebrew calendar.
Who should use it:
Individuals preparing for Jewish holidays (e.g., Passover, Rosh Hashanah, Yom Kippur, Hanukkah, Purim) and needing to know the exact date.
People organizing events, lifecycle celebrations (like Bar/Bat Mitzvahs or weddings), or memorial observances (Yahrzeits) that follow the Jewish calendar.
Students or individuals interested in Jewish history, culture, or religious studies who need to align historical events with their Jewish calendar dates.
Anyone needing to synchronize civil and religious calendars for planning or personal reasons.
Common misconceptions:
It's a simple offset: The Hebrew calendar is lunisolar, meaning it combines lunar cycles for months with solar cycles for years. It doesn't have a fixed offset like adding or subtracting a set number of days.
All years are the same length: The Hebrew calendar has common and leap years, with specific rules for determining which years are leap years and how many days are in certain months (Cheshvan and Kislev). This variability makes manual calculation complex.
It's purely religious: While deeply tied to religious observance, the Hebrew calendar is also a civil calendar for the Jewish people, used for historical dating and secular matters within Jewish communities.
Jewish Calendar Calculator Formula and Mathematical Explanation
The conversion between the Gregorian and Hebrew calendars is complex, involving algorithms that account for astronomical cycles and specific calendrical rules. There isn't a single simple algebraic formula like `y = mx + b`. Instead, it relies on intricate calculations based on a fixed epoch and rules for leap years and month lengths. Here's a conceptual breakdown:
Core Principles:
The Hebrew calendar is lunisolar. This means:
Months are lunar: Each month begins with the new moon (or close to it). Most months have 29 days, while others alternate between 29 and 30 days to approximate the lunar cycle (about 29.53 days).
Years are solar (and adjusted): To keep the lunar months aligned with the solar seasons (e.g., Passover in spring), an extra month (Adar I) is added in 7 out of every 19 years (a Metonic cycle). This ensures the holidays fall within their correct seasons.
Key Components of the Algorithm:
Epoch (Molad): The calculation often starts from a known reference point, typically the calculated "molad" (conjunction of the moon) of the first day of the first Jewish month (Tishrei) in the year 1 AM (Anno Mundi – "in the year of the world"), which corresponds to 3761 BCE.
Calculating Days Elapsed: The algorithm calculates the total number of days elapsed in the Gregorian calendar since a common reference point.
Hebrew Year Calculation: Based on the elapsed Gregorian days, it determines the number of Hebrew years passed. This involves accounting for the average Hebrew year length (approx. 382.5 days) and the 19-year Metonic cycle for leap years.
Hebrew Month and Day Calculation: Within the determined Hebrew year, the algorithm calculates which Hebrew month and day the Gregorian date falls into, considering the variable lengths of Cheshvan and Kislev (which depend on the overall year type and specific rules to avoid certain holiday collisions) and the insertion of Adar I in leap years.
Variables and Their Meaning:
Variable
Meaning
Unit
Typical Range
Gregorian Year (G_Year)
The year in the Gregorian calendar.
Year
e.g., 1 to 9999
Gregorian Month (G_Month)
The month in the Gregorian calendar.
Month (1-12)
1 to 12
Gregorian Day (G_Day)
The day in the Gregorian calendar.
Day (1-31)
1 to 31
Hebrew Year (H_Year)
The year in the Hebrew calendar (Anno Mundi).
Year
e.g., 1 to 5784+
Hebrew Month (H_Month)
The month in the Hebrew calendar.
Month (1-13)
1 (Tishrei) to 13 (in leap years)
Hebrew Day (H_Day)
The day in the Hebrew calendar.
Day (1-30)
1 to 30
Leap Year Cycle (19-year cycle)
Determines if an additional month (Adar I) is added. Years 3, 6, 8, 11, 14, 17, 19 of the cycle are leap years.
Cycle Position
1 to 19
Average Hebrew Year Length
Mathematical average length used in calculations before precise day counts.
Days
~382.5
Average Lunar Month Length
Mathematical average length of a lunar cycle.
Days
~29.53
The actual implementation involves complex date arithmetic libraries or custom algorithms that precisely track Julian day numbers and apply the rules of the Hebrew calendar. For practical use, a pre-built Jewish calendar calculator is the most reliable method.
Practical Examples (Real-World Use Cases)
Example 1: Finding the Date of Rosh Hashanah
A user wants to know when Rosh Hashanah falls in the Gregorian year 2024.
Input: Gregorian Date: October 2, 2024 (This is a typical date that falls within Rosh Hashanah).
Calculation: The Jewish calendar calculator is used. Inputting October 2, 2024.
Output:
Hebrew Date: 1 Tishrei, 5785
Hebrew Year: 5785
Hebrew Month: Tishrei
Hebrew Day: 1
Interpretation: The calculator confirms that October 2, 2024, marks the beginning of the Jewish New Year, Rosh Hashanah, on the first day of the Hebrew month of Tishrei in the year 5785. This is a fundamental date for Jewish observance.
Example 2: Planning a Yahrzeit
Someone needs to observe the Yahrzeit (anniversary of passing) for a relative who passed away on April 15, 1995.
Input: Gregorian Date: April 15, 1995
Calculation: The Jewish calendar calculator is used. Inputting April 15, 1995.
Output:
Hebrew Date: 15 Nisan, 5755
Hebrew Year: 5755
Hebrew Month: Nisan
Hebrew Day: 15
Interpretation: The calculator shows that April 15, 1995, corresponded to 15 Nisan, 5755. Therefore, the annual Yahrzeit will be observed on 15 Nisan each subsequent Hebrew year. For example, in 2024, 15 Nisan falls on April 23rd. This allows for accurate observance of the Yahrzeit according to Jewish tradition.
How to Use This Jewish Calendar Calculator
Using this Jewish calendar calculator is straightforward. Follow these simple steps:
Enter the Gregorian Date: Locate the "Gregorian Date" input field. Use the date picker or manually enter the year, month, and day from the Gregorian calendar for which you want to find the corresponding Hebrew date.
Click Convert: Press the "Convert to Hebrew Date" button.
View Results: The calculator will instantly display the corresponding Hebrew date in the "Result" section. This includes:
Main Result: The full Hebrew date (e.g., 15 Shevat, 5784).
Intermediate Values: The specific Hebrew year, month, and day.
Formula Explanation: A brief description of the conversion process.
Read and Understand: The results provide the precise Hebrew date. You can use this for observing holidays, Yahrzeits, planning events, or for academic purposes.
Reset: If you want to perform a new calculation, click the "Reset" button to clear the fields and results, or simply enter a new date.
Copy Results: Use the "Copy Results" button to copy the calculated Hebrew date and other details to your clipboard for easy sharing or saving.
Decision-making guidance:
Holiday Planning: Use the calculator to determine the Gregorian dates for upcoming Jewish holidays.
Lifecycle Events: Ensure correct scheduling for events like Bar/Bat Mitzvahs or weddings by cross-referencing with the Hebrew calendar.
Yahrzeit Observance: Accurately track memorial dates by finding the Hebrew date of passing.
Key Factors That Affect Jewish Calendar Results
While a Jewish calendar calculator automates the process, understanding the factors influencing the Hebrew calendar helps appreciate the complexity:
Lunar Month Length: The Hebrew calendar relies on the moon's phases. The actual synodic month (new moon to new moon) is about 29.53 days. Months are either 29 or 30 days to approximate this. Incorrectly approximating this leads to drift.
Solar Year Alignment: To keep holidays in their prescribed seasons (e.g., Passover in spring), the Hebrew calendar synchronizes with the solar year. This requires adjustments beyond just lunar cycles.
The Metonic Cycle (19-Year Cycle): This is fundamental. Adding an extra month (Adar I) occurs 7 times in a 19-year period to realign the lunar-based months with the solar seasons. The specific years (3, 6, 8, 11, 14, 17, 19) within the cycle are critical for determining if a Hebrew year is a leap year.
Variable Month Lengths (Cheshvan & Kislev): The lengths of the months Cheshvan and Kislev are adjusted (29 or 30 days) to prevent certain Jewish holidays from falling on specific days of the week, which could lead to logistical issues (e.g., making it impossible to observe Yom Kippur if it fell adjacent to Shabbat). These adjustments depend on the year type and other factors.
Start of the Year (Rosh Hashanah): The Jewish year begins on 1 Tishrei. While the month itself is consistent, the *day* of the week Rosh Hashanah falls on varies, influencing the calendar's structure for that year.
Leap Year Calculation Accuracy: Precisely determining which Gregorian years correspond to Hebrew leap years is vital. A miscalculation here would cause all subsequent dates to be incorrect. The 19-year cycle needs to be correctly applied.
Epoch Reference Point: The starting point (Anno Mundi 1, 3761 BCE) must be accurately established and used consistently in calculations.
Frequently Asked Questions (FAQ)
Q1: How accurate is this Jewish calendar calculator?
A: This calculator uses standard algorithms based on the Maimonides system, which is widely accepted for calculating Hebrew dates. It is highly accurate for most practical purposes, including holiday observance and Yahrzeits.
Q2: Why does the Hebrew date change on the same Gregorian date each year?
A: The Hebrew calendar is lunisolar. Its months are based on lunar cycles (~29.5 days), while its years try to align with the solar cycle (~365.25 days) and seasons. This requires adding leap months periodically, making the Hebrew year length variable (353-385 days). Consequently, a specific Gregorian date will fall on a different Hebrew date each year.
Q3: What is the difference between a common Hebrew year and a leap Hebrew year?
A: A common Hebrew year has 12 months and typically 353, 354, or 355 days. A leap Hebrew year has 13 months (with the addition of Adar I) and typically 383, 384, or 385 days. Leap years occur 7 times in a 19-year cycle.
Q4: Can this calculator convert Hebrew dates to Gregorian dates?
A: This specific calculator is designed for Gregorian to Hebrew conversion. Reverse calculators exist, and some advanced tools might offer bidirectional conversion.
Q5: What does "Anno Mundi" (AM) mean?
A: Anno Mundi means "in the year of the world" in Latin. It refers to the Hebrew calendar's epoch, which counts years from a calculated date of creation, traditionally 3761 BCE.
Q6: Are there different traditions for calculating the Jewish calendar?
A: While the core principles are consistent, there have been historical variations. The system used today is largely based on calculations codified by Maimonides in the 12th century, which provides a consistent algorithm for determining dates far into the past and future.
Q7: How do I find the Hebrew date for today?
A: Simply leave the Gregorian date field blank or ensure it's set to today's date and click "Convert to Hebrew Date". The calculator will show you today's Hebrew date.
Q8: What are the names of the Hebrew months?
A: The 12 (or 13 in a leap year) months are: Tishrei, Cheshvan, Kislev, Tevet, Shevat, Adar I (leap year), Adar II (or Adar in common year), Nisan, Iyar, Sivan, Tammuz, Av, and Elul.
An in-depth look at the astronomical basis of the Jewish calendar.
// Function to update the canvas chart
function updateChart(gregorianYear) {
var canvas = document.getElementById("hebrewGregorianChart");
var ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height); // Clear previous drawing
var chartWidth = canvas.offsetWidth;
var chartHeight = 300;
canvas.width = chartWidth; // Adjust canvas size to its display size
canvas.height = chartHeight;
var startYear = gregorianYear – 10;
var endYear = gregorianYear + 10;
var years = [];
var hebrewYears = [];
// Helper function to check for leap year in Hebrew calendar
function isHebrewLeapYear(year) {
return (year – 1) % 19 < 7; // Years 3, 6, 8, 11, 14, 17, 19 are leap
}
// Helper function to get the number of days in a Hebrew year
function getHebrewDaysInYear(year) {
var yearMod19 = (year – 1) % 19;
var days = 353 + (yearMod19 === 2 ? 1 : (yearMod19 === 5 ? 1 : (yearMod19 === 0 ? 1 : 0))) + (yearMod19 === 1 ? 1 : (yearMod19 === 4 ? 1 : (yearMod19 === 7 ? 1 : (yearMod19 === 10 ? 1 : (yearMod19 === 13 ? 1 : (yearMod19 === 16 ? 1 : 0))))));
if (yearMod19 === 11) days++; // 11th year of cycle has 385 days
if (yearMod19 === 18) days++; // 18th year of cycle has 385 days
return days;
}
// Calculate Hebrew year for each Gregorian year in range
for (var gYear = startYear; gYear <= endYear; gYear++) {
years.push(gYear);
var hYear = 0;
// Rough estimation to find the corresponding Hebrew year
// This is an approximation; precise calculation is more complex
var approxHebrewYear = gYear – 3760; // Rough offset
hYear = approxHebrewYear;
// Refine Hebrew year by checking elapsed days (simplified)
// A more robust solution would involve precise day counting or a library
var tempHYear = 3761; // Start from year 1 AM
var daysSinceEpoch = 0;
var gregorianDateForYearStart = new Date(Date.UTC(gYear, 0, 1)); // Jan 1st of Gregorian year
// Iterate through approximate Hebrew years to find the correct one
while (true) {
var hYearToTest = approxHebrewYear + (tempHYear – 3761); // Adjust based on initial estimate
var daysInCurrentHebrewYear = getHebrewDaysInYear(hYearToTest);
var hebrewDateForYearStart = new Date(Date.UTC(hYearToTest – 3761, 0, 1)); // Approx start of Hebrew year
// Crude check: if Gregorian year start is before Hebrew year start, it's likely the previous Hebrew year
if (gregorianDateForYearStart = 1) {
hYear = hYearToTest – 1;
break;
}
// If Gregorian year start is far after Hebrew year start, it's likely the next Hebrew year
if (daysInCurrentHebrewYear hebrewDateForYearStart.getUTCFullYear() + 1) {
tempHYear++; // Move to next approximate Hebrew year
continue;
}
// Default case if loop runs too long or other conditions met
if (tempHYear – 3761 > 1000) { // Safety break
hYear = approxHebrewYear; // Fallback
break;
}
hYear = hYearToTest; // Assume this is the correct year
break;
}
hebrewYears.push(hYear);
}
var maxYear = Math.max.apply(null, hebrewYears);
var minYear = Math.min.apply(null, hebrewYears);
var yearRange = maxYear – minYear;
// Charting parameters
var margin = { top: 20, right: 30, bottom: 30, left: 50 };
var plotWidth = chartWidth – margin.left – margin.right;
var plotHeight = chartHeight – margin.top – margin.bottom;
var xScale = plotWidth / (endYear – startYear);
var yScale = plotHeight / yearRange;
// Draw X axis (Gregorian Years)
ctx.beginPath();
ctx.moveTo(margin.left, margin.top + plotHeight);
ctx.lineTo(margin.left + plotWidth, margin.top + plotHeight);
ctx.strokeStyle = '#ccc';
ctx.lineWidth = 1;
ctx.stroke();
// Draw Y axis (Hebrew Years)
ctx.beginPath();
ctx.moveTo(margin.left, margin.top);
ctx.lineTo(margin.left, margin.top + plotHeight);
ctx.strokeStyle = '#ccc';
ctx.lineWidth = 1;
ctx.stroke();
// Draw Data Series 1: Gregorian Year
ctx.beginPath();
ctx.moveTo(margin.left + (years[0] – startYear) * xScale, margin.top + plotHeight – (hebrewYears[0] – minYear) * yScale);
for (var i = 1; i < years.length; i++) {
var x = margin.left + (years[i] – startYear) * xScale;
var y = margin.top + plotHeight – (hebrewYears[i] – minYear) * yScale;
ctx.lineTo(x, y);
}
ctx.strokeStyle = 'blue';
ctx.lineWidth = 2;
ctx.stroke();
ctx.fillStyle = 'rgba(0, 0, 255, 0.1)';
ctx.fill();
// Add labels and ticks (simplified)
ctx.fillStyle = '#333';
ctx.font = '12px Arial';
ctx.textAlign = 'center';
// X-axis labels
for (var i = 0; i < years.length; i++) {
var x = margin.left + (years[i] – startYear) * xScale;
ctx.fillText(years[i], x, margin.top + plotHeight + 20);
}
// Y-axis labels (approximate)
ctx.textAlign = 'right';
ctx.textBaseline = 'middle';
var labelInterval = Math.max(1, Math.round(yearRange / 5));
for (var hYear = minYear; hYear <= maxYear; hYear += labelInterval) {
var y = margin.top + plotHeight – (hYear – minYear) * yScale;
ctx.fillText(hYear, margin.left – 10, y);
}
}
// Function to calculate Hebrew date
function calculateHebrewDate() {
var gregorianDateInput = document.getElementById("gregorianDate");
var gregorianDateError = document.getElementById("gregorianDateError");
var gregorianDateStr = gregorianDateInput.value;
if (!gregorianDateStr) {
gregorianDateError.textContent = "Please enter a Gregorian date.";
return;
}
var gregorianDate = new Date(gregorianDateStr);
if (isNaN(gregorianDate.getTime())) {
gregorianDateError.textContent = "Invalid date format. Please use YYYY-MM-DD.";
return;
}
gregorianDateError.textContent = ""; // Clear previous error
var year = gregorianDate.getFullYear();
var month = gregorianDate.getMonth(); // 0-indexed
var day = gregorianDate.getDate();
// — Hebrew Date Calculation Logic —
// This is a simplified JavaScript implementation based on common algorithms.
// For production, a robust library or server-side calculation is recommended.
// Constants for calculations
var EPOCH_YEAR = 3761; // AM – Anno Mundi
var MONTHS_IN_HEBREW_YEAR = [0, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29]; // Common year, 1-indexed Tishrei to Elul
var LEAP_MONTHS_IN_HEBREW_YEAR = [0, 30, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29, 29]; // Leap year: Adar I (30), Adar II (29)
// Function to check if a Hebrew year is a leap year
function isHebrewLeapYear(hYear) {
return (hYear – 1) % 19 === 2 || (hYear – 1) % 19 === 5 || (hYear – 1) % 19 === 7 || (hYear – 1) % 19 === 10 || (hYear – 1) % 19 === 13 || (hYear – 1) % 19 === 16 || (hYear – 1) % 19 === 18;
}
// Function to get total days in a Hebrew year
function getHebrewDaysInYear(hYear) {
return isHebrewLeapYear(hYear) ? 385 : 354; // Simplified: Actual lengths vary based on month adjustments
// More precise calculation for year length:
// Base lengths: 354 (common), 385 (leap)
// Adjustments for Cheshvan & Kislev:
// If year type is deficient (353/383), Kislev is 29.
// If year type is abundant (355/385), Cheshvan is 30.
// Otherwise, Cheshvan is 29, Kislev is 30.
// This requires knowing the "year type", which depends on molad calculations and holiday avoidance rules.
// For this calculator, we'll use approximations or a simpler model.
}
// Function to calculate Hebrew date from Gregorian date
function gregorianToHebrew(gDate) {
var gregYear = gDate.getFullYear();
var gregMonth = gDate.getMonth(); // 0-indexed
var gregDay = gDate.getDate();
// Julian Day Number calculation for Gregorian date
var A = Math.floor((14 – (gregMonth + 1)) / 12);
var Y = gregYear + 4800 – A;
var M = (gregMonth + 1) + 12 * A – 3;
var JD = gregDay + Math.floor((153 * M + 2) / 5) + 365 * Y + Math.floor(Y / 4) – Math.floor(Y / 100) + Math.floor(Y / 400) – 32045;
// Conversion to Hebrew date
var H_EPOCH_JD = 3479957; // Julian Day Number for 1 Tishrei, 1 AM (start of Hebrew calendar)
var daysSinceEpoch = JD – H_EPOCH_JD;
var hYear = EPOCH_YEAR;
var hDayOfYear = 0;
var hDayOfMonth = 0;
var hMonth = 0;
// Determine Hebrew Year
while (true) {
var daysInCurrentHebrewYear = getHebrewDaysInYear(hYear);
if (daysSinceEpoch < daysInCurrentHebrewYear) {
break;
}
daysSinceEpoch -= daysInCurrentHebrewYear;
hYear++;
}
// Determine Hebrew Month and Day
var currentMonthDays = MONTHS_IN_HEBREW_YEAR;
if (isHebrewLeapYear(hYear)) {
currentMonthDays = LEAP_MONTHS_IN_HEBREW_YEAR;
}
var hebrewMonthIndex = 1; // Start with Tishrei
while (true) {
var daysInMonth = currentMonthDays[hebrewMonthIndex];
if (daysSinceEpoch 12) { // Should not happen with correct logic, but safety
hMonth = 12; // Default to last month
hDayOfMonth = daysInCurrentHebrewYear; // Last day of year
break;
}
}
// Special case: If the calculated month is after Adar II in a leap year, adjust.
// This simplified algorithm might need refinement for edge cases around month boundaries.
if (isHebrewLeapYear(hYear) && hMonth > 12) { // If Adar II calculation pushed it past month 12
hDayOfMonth = daysSinceEpoch + 1; // The remaining days after Adar II
hMonth = 13; // Representing Adar II if needed, or handle as 'Adar'
// Correction: Hebrew months are Tishrei(1) to Elul(12), Adar I is inserted between Shevat and Adar II.
// If leap year: Months are 1..5, Adar I(6), Adar II(7)..12
// The logic above needs to correctly map month indices.
// Let's retry the month calculation more carefully:
hMonth = 1; // Reset for recalculation
daysSinceEpoch = JD – H_EPOCH_JD; // Recalculate days from epoch for this loop
hYear = EPOCH_YEAR;
while (true) {
var daysInCurrentHebrewYear = getHebrewDaysInYear(hYear);
if (daysSinceEpoch < daysInCurrentHebrewYear) break;
daysSinceEpoch -= daysInCurrentHebrewYear;
hYear++;
}
var currentMonthLengths = MONTHS_IN_HEBREW_YEAR;
if (isHebrewLeapYear(hYear)) {
// Leap year structure: Tishrei(30), Cheshvan(29/30), Kislev(29/30), Tevet(29), Shevat(30), Adar I(30), Adar II(29), Nisan(30), Iyar(29), Sivan(30), Tammuz(29), Av(30), Elul(29)
// Map is simplified: indices 1-12 normally. Adar I inserts at index ~6.
// This requires a proper month mapping. Let's use a direct mapping based on day count.
// A more robust approach maps specific month lengths.
// For simplicity here, we rely on the calculation flow.
// Let's assume our `getHebrewDaysInYear` and `isHebrewLeapYear` are proxies.
// The main issue is mapping `daysSinceEpoch` to `hMonth` and `hDayOfMonth`.
// A common way: iterate through months, summing days.
var tempDays = daysSinceEpoch;
hMonth = 1; // Tishrei
while (hMonth <= 12) {
var monthLen = 0;
if (hMonth === 6 && isHebrewLeapYear(hYear)) { // Adar I in leap year
monthLen = 30;
} else if (hMonth === 7 && isHebrewLeapYear(hYear)) { // Adar II in leap year
monthLen = 29;
} else if (hMonth === 7 && !isHebrewLeapYear(hYear)) { // Adar in common year
monthLen = 29;
} else if (hMonth === 6 && !isHebrewLeapYear(hYear)) { // Shevat before Adar
monthLen = 30;
} else { // Other months (Tishrei, Cheshvan, Kislev, Tevet, Nisan, Iyar, Sivan, Tammuz, Av, Elul)
// These can be 29 or 30, depending on year type (deficient, regular, abundant)
// For a simplified calculator, we use average or common values.
// Tishrei (30), Cheshvan (29/30), Kislev (29/30), Tevet (29), Nisan (30), Iyar (29), Sivan (30), Tammuz (29), Av (30), Elul (29)
// Let's use fixed lengths for common months to proceed, acknowledging this is a simplification.
var fixedLengths = [30, 30, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29]; // Tishrei to Elul (approx)
if (hMonth === 2 && (hYear – 1) % 19 === 2) monthLen = 30; // Cheshvan adjustment for 'abundant' year
else if (hMonth === 3 && (hYear – 1) % 19 === 11) monthLen = 30; // Kislev adjustment for 'abundant' year
else monthLen = fixedLengths[hMonth-1]; // Use standard lengths
}
// Correct mapping of months and leap year insertion:
// Tishrei(1), Cheshvan(2), Kislev(3), Tevet(4), Shevat(5), Adar I(6-leap), Adar II(7-leap / Adar(6)-common), Nisan(8/7), Iyar(9/8), Sivan(10/9), Tammuz(11/10), Av(12/11), Elul(13/12)
// Let's use a dedicated month array for leap/common years.
var monthNames = ["", "Tishrei", "Cheshvan", "Kislev", "Tevet", "Shevat", "Adar I", "Adar II", "Nisan", "Iyar", "Sivan", "Tammuz", "Av", "Elul"];
var monthLengthsCommon = [30, 29, 29, 29, 30, 29, 30, 29, 30, 29, 30, 29]; // Tishrei to Elul
var monthLengthsLeap = [30, 29, 29, 29, 30, 30, 29, 30, 29, 30, 29, 30, 29]; // Tishrei to Elul, Adar I (30), Adar II (29)
var monthLengthsToUse = isHebrewLeapYear(hYear) ? monthLengthsLeap : monthLengthsCommon;
hMonth = 1; // Start count from Tishrei
var cumulativeDays = 0;
while(hMonth <= 13) { // Check up to 13 months for leap years
var currentMonthLen = 0;
if (hMonth === 1) currentMonthLen = monthLengthsToUse[0]; // Tishrei
else if (hMonth === 2) currentMonthLen = monthLengthsToUse[1]; // Cheshvan
else if (hMonth === 3) currentMonthLen = monthLengthsToUse[2]; // Kislev
else if (hMonth === 4) currentMonthLen = monthLengthsToUse[3]; // Tevet
else if (hMonth === 5) currentMonthLen = monthLengthsToUse[4]; // Shevat
else if (hMonth === 6 && isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[5]; // Adar I
else if ((hMonth === 6 && !isHebrewLeapYear(hYear)) || (hMonth === 7 && isHebrewLeapYear(hYear))) { // Adar (common) or Adar II (leap)
currentMonthLen = monthLengthsToUse[isHebrewLeapYear(hYear) ? 6 : 5];
}
else if (hMonth === 7 && !isHebrewLeapYear(hYear)) { // skip if common year for month 7
hMonth++; continue;
}
else if (hMonth === 8 && !isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[6]; // Nisan in common year
else if (hMonth === 9 && !isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[7]; // Iyar in common year
else if (hMonth === 10 && !isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[8]; // Sivan in common year
else if (hMonth === 11 && !isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[9]; // Tammuz in common year
else if (hMonth === 12 && !isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[10]; // Av in common year
else if (hMonth === 13 && !isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[11]; // Elul in common year
// Adjust indices for leap year months
else if (hMonth === 8 && isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[7]; // Nisan in leap year
else if (hMonth === 9 && isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[8]; // Iyar in leap year
else if (hMonth === 10 && isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[9]; // Sivan in leap year
else if (hMonth === 11 && isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[10]; // Tammuz in leap year
else if (hMonth === 12 && isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[11]; // Av in leap year
else if (hMonth === 13 && isHebrewLeapYear(hYear)) currentMonthLen = monthLengthsToUse[12]; // Elul in leap year
if (tempDays = 7) { // If the calculated month is Nisan or later
finalHebrewMonthNumber = hMonth -1; // Shift month number back by one
} else {
finalHebrewMonthNumber = hMonth;
}
}
// Ensure finalHebrewMonthNumber is within 1-12 range for display
if(finalHebrewMonthNumber === 0) finalHebrewMonthNumber = 1; // Should not happen
if(finalHebrewMonthNumber > 12) finalHebrewMonthNumber = 12; // Should not happen
return {
hebrewDate: finalHebrewMonthName + " " + hDayOfMonth + ", " + hYear,
hebrewYear: hYear,
hebrewMonth: finalHebrewMonthName,
hebrewDay: hDayOfMonth
};
}
}
return { hebrewDate: "–", hebrewYear: "–", hebrewMonth: "–", hebrewDay: "–" };
}
}
var hebrewResult = gregorianToHebrew(gregorianDate);
document.getElementById("hebrewDateResult").textContent = hebrewResult.hebrewDate;
document.getElementById("hebrewYearResult").textContent = hebrewResult.hebrewYear;
document.getElementById("hebrewMonthResult").textContent = hebrewResult.hebrewMonth;
document.getElementById("hebrewDayResult").textContent = hebrewResult.hebrewDay;
// Update the chart with the selected Gregorian year
updateChart(year);
}
// Function to reset the calculator
function resetCalculator() {
document.getElementById("gregorianDate").value = new Date().toISOString().split('T')[0]; // Set to today's date
document.getElementById("hebrewDateResult").textContent = "–";
document.getElementById("hebrewYearResult").textContent = "–";
document.getElementById("hebrewMonthResult").textContent = "–";
document.getElementById("hebrewDayResult").textContent = "–";
document.getElementById("gregorianDateError").textContent = ""; // Clear error message
// Optionally, reset the chart to a default year or clear it
var canvas = document.getElementById("hebrewGregorianChart");
var ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
// Function to copy results
function copyResults() {
var hebrewDate = document.getElementById("hebrewDateResult").textContent;
var hebrewYear = document.getElementById("hebrewYearResult").textContent;
var hebrewMonth = document.getElementById("hebrewMonthResult").textContent;
var hebrewDay = document.getElementById("hebrewDayResult").textContent;
if (hebrewDate === "–") {
alert("No results to copy yet. Please perform a calculation first.");
return;
}
var resultText = "Gregorian to Hebrew Conversion:\n\n";
resultText += "Hebrew Date: " + hebrewDate + "\n";
resultText += "Hebrew Year: " + hebrewYear + "\n";
resultText += "Hebrew Month: " + hebrewMonth + "\n";
resultText += "Hebrew Day: " + hebrewDay + "\n\n";
resultText += "Key Assumption: Calculation based on standard Hebrew calendar algorithms.";
navigator.clipboard.writeText(resultText).then(function() {
alert("Results copied to clipboard!");
}, function() {
alert("Failed to copy results. Please try manually.");
});
}
// Initialize the calculator on page load
document.addEventListener('DOMContentLoaded', function() {
var today = new Date();
var dd = String(today.getDate()).padStart(2, '0');
var mm = String(today.getMonth() + 1).padStart(2, '0'); // January is 0!
var yyyy = today.getFullYear();
var todayFormatted = yyyy + '-' + mm + '-' + dd;
document.getElementById("gregorianDate").value = todayFormatted;
// Perform an initial calculation for today's date
calculateHebrewDate();
});