Discover your birth date on the Chinese Lunar Calendar and understand its cultural significance.
Lunar Birthday Calculator
January
February
March
April
May
June
July
August
September
October
November
December
Your Lunar Birthday Details
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Lunar Year Animal—
Lunar Month—
Lunar Day—
Calculation Method: This calculator converts your Gregorian (solar) birth date into the corresponding Chinese Lunar calendar date. This involves complex astronomical calculations and historical calendar rules, accounting for leap months and the varying lengths of lunar months. The lunar year typically begins between January 21st and February 20th of the Gregorian calendar. The lunar year's animal zodiac is determined by the 12-year cycle.
Key Calendar Information
Component
Gregorian
Lunar
Year
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—
Month
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—
Day
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Zodiac Animal
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Chart illustrating the conversion from Gregorian to Lunar dates.
What is the Chinese Lunar Birthday Calculator?
The Chinese Lunar Birthday Calculator is a digital tool designed to help individuals determine their birth date according to the traditional Chinese lunisolar calendar. Unlike the Gregorian calendar, which is purely solar-based, the Chinese calendar is a complex system that tracks both the moon's phases and the sun's position. This makes calculating a lunar birthday a nuanced process, as the start of the year and the length of months can differ significantly from the solar calendar we commonly use.
This calculator is invaluable for anyone interested in understanding their Chinese heritage, celebrating traditional festivals, or seeking astrological insights based on the Chinese zodiac. It bridges the gap between modern Western dating systems and the ancient Chinese calendrical system, offering a precise conversion for any given Gregorian date.
Who Should Use It?
Several groups of people can benefit from using a Chinese Lunar Birthday Calculator:
Individuals of Chinese descent who wish to connect with their cultural roots and celebrate birthdays according to tradition.
People interested in Chinese astrology and seeking to determine their lunar birth animal and its associated traits.
Anyone planning to attend or host events during traditional Chinese festivals, such as Chinese New Year or the Mid-Autumn Festival, which are all based on the lunar calendar.
Historians, researchers, or students studying Chinese culture, history, or calendrical systems.
Individuals curious about the differences between the Gregorian and Chinese lunar calendars.
Common Misconceptions
One common misconception is that the Chinese Lunar New Year always falls on January 1st. In reality, it varies each year, occurring between January 21st and February 20th on the Gregorian calendar. Another is that the lunar calendar is purely lunar; it is actually lunisolar, meaning it incorporates solar elements to keep seasons aligned. Some also believe that every lunar year has 12 months, but leap months are added periodically to synchronize the calendar with the solar year, making some years have 13 months.
Chinese Lunar Birthday Calculator Formula and Mathematical Explanation
The accurate conversion from the Gregorian (solar) calendar to the Chinese lunisolar calendar is a sophisticated process. It relies on astronomical observations and a set of historical rules, rather than a simple arithmetic formula. Modern calculators utilize algorithms that simulate these rules and astronomical data.
The Core Challenge: Lunisolar Synchronization
The fundamental challenge lies in synchronizing the lunar cycle (approximately 29.53 days) with the solar year (approximately 365.24 days). A year of 12 lunar months is about 354 days, falling short of the solar year by roughly 11 days. To compensate, an extra "leap month" is inserted roughly every 2-3 years, making some years consist of 13 months.
The Chinese Lunar Calendar also defines the start of the year. The Lunar New Year (Spring Festival) is the second new moon after the Winter Solstice. The calculator essentially needs to find this specific new moon and then count forward lunar months and days from there, factoring in leap months and the specific Gregorian date provided.
Key Components and Algorithms
While a simple formula isn't practical for direct human calculation, the underlying principles involve:
Astronomical Data: Precise ephemeris data for the sun and moon are required.
New Moon Calculation: Algorithms to precisely calculate the timing of new moons.
Winter Solstice Determination: Pinpointing the Winter Solstice is crucial for the start of the year.
Leap Month Rules: Complex rules dictate when a leap month is added. A month is designated as a leap month if it occurs between two consecutive Winter Solstices and does not contain a major solar term (like the start of spring, summer, autumn, or winter). Furthermore, certain months cannot be leap months.
Day and Month Tracking: Once the start of the year and month lengths are established, the calculator counts forward to the target Gregorian date.
Variables Table
For understanding the context of the calculation, consider these variables:
Lunar Calendar Variables
Variable
Meaning
Unit
Typical Range
Gregorian Date
The input date in the standard solar calendar.
Year, Month, Day
e.g., 1990-2024
Lunar New Year (Spring Festival)
The first day of the first lunar month.
Gregorian Date
Jan 21 – Feb 20
Lunar Month Length
Duration of a lunar month (synodic month).
Days
29 or 30
Lunar Year Length
Duration of a lunar year (12 or 13 lunar months).
Days
~354 (12 months) or ~384 (13 months)
Leap Month
An intercalary month added to synchronize lunar and solar cycles.
Let's explore some practical scenarios using the Chinese Lunar Birthday Calculator.
Example 1: Connecting with Ancestral Traditions
Scenario: Sarah was born on March 5, 1985, in the Gregorian calendar. Her grandmother often spoke of celebrating birthdays according to the Chinese lunar calendar and mentioned that Sarah was born in the year of the Ox.
Inputs:
Gregorian Year: 1985
Gregorian Month: 3 (March)
Gregorian Day: 5
Calculator Output:
Primary Result: February 15, 1985 (Lunar)
Lunar Year Animal: Ox
Lunar Month: 2 (February)
Lunar Day: 26
Lunar Year: 1985
Interpretation: Sarah can now accurately identify her lunar birthday as February 15, 1985. This information allows her to celebrate her birthday on the correct lunar date, potentially aligning with family traditions or gaining a deeper understanding of her birth year's zodiac sign, the Ox, which is often associated with diligence and reliability in Chinese culture. The calculator confirms the Ox year, validating her grandmother's recollection.
Example 2: Planning for a Traditional Festival Celebration
Scenario: David wants to organize a birthday party that incorporates elements of Chinese culture for his friend, Mei, who was born on September 18, 1992. He knows Mei's birthday often falls near the Mid-Autumn Festival or Chinese New Year.
Inputs:
Gregorian Year: 1992
Gregorian Month: 9 (September)
Gregorian Day: 18
Calculator Output:
Primary Result: September 22, 1992 (Lunar)
Lunar Year Animal: Monkey
Lunar Month: 8 (August)
Lunar Day: 22
Lunar Year: 1992
Interpretation: David learns that Mei's lunar birthday is September 22, 1992. He can check a Chinese festival calendar and see that the Mid-Autumn Festival in 1992 fell on September 22nd. This means Mei's birthday aligns perfectly with this significant harvest festival, known for family gatherings, mooncakes, and lanterns. David can now plan a culturally relevant party incorporating these themes, making it a more meaningful celebration for Mei. The calculator also reveals her lunar zodiac is the Monkey, known for its wit and charm.
How to Use This Chinese Lunar Birthday Calculator
Using the Chinese Lunar Birthday Calculator is straightforward. Follow these simple steps:
Enter Your Gregorian Birth Date: In the input fields provided, accurately enter your year, month, and day of birth according to the Gregorian (solar) calendar. Use the format requested (e.g., YYYY for year, MM for month, DD for day).
Validate Input: Ensure all fields are filled correctly. The calculator will perform inline validation to check for common errors like negative numbers or impossible dates.
Click 'Calculate': Press the "Calculate" button. The calculator will process your input and display your corresponding lunar birthday.
Review the Results: You will see your primary lunar birthday date prominently displayed. Below this, you'll find key intermediate values: the Lunar Year Animal (Zodiac), the Lunar Month, and the Lunar Day. A table will summarize the Gregorian and Lunar details.
Understand the Data: Read the "Calculation Method" explanation to grasp how the conversion is performed. The chart provides a visual representation of the date conversion.
Reset or Copy: Use the "Reset" button to clear the fields and start over with a new date. The "Copy Results" button allows you to easily transfer the calculated lunar birthday and related details for your records or sharing.
How to Read Results
Primary Result: This is your birth date on the Chinese Lunar Calendar (e.g., "February 15, 1985 Lunar").
Lunar Year Animal: Your Chinese Zodiac sign for the year you were born (e.g., "Ox").
Lunar Month & Day: The specific month and day within the lunar calendar year. Note that lunar months are numbered (1st, 2nd, etc.), and some years might have a "Leap Month."
Table: Provides a side-by-side comparison of your Gregorian birth date and its Lunar equivalent, including the Zodiac animal.
Decision-Making Guidance
The results from this calculator can inform several decisions:
Celebration Planning: Decide whether to celebrate your birthday on the Gregorian date, the Lunar date, or both. Many people of Chinese heritage celebrate on the lunar date to honor tradition.
Astrological Insights: Use your Lunar Year Animal and birth month (if relevant to a specific lunar tradition) for astrological readings or understanding personality traits associated with your sign.
Festival Alignment: Determine if your birthday falls close to major Chinese festivals, allowing for combined celebrations or understanding its place within the traditional calendar year.
Key Factors That Affect Chinese Lunar Birthday Results
While the Chinese Lunar Birthday Calculator provides a direct conversion, several underlying factors influence why the lunisolar calendar works the way it does and why precise calculation is complex:
Lunar Cycle Length: The synodic month (time between two new moons) is approximately 29.53 days. This non-integer value means lunar months must alternate between 29 and 30 days to approximate the cycle. This fundamental aspect dictates the day-to-day progression of the lunar calendar.
Solar Year Length: The tropical year is approximately 365.24 days. The discrepancy between 12 lunar months (~354 days) and the solar year (~365 days) is about 11 days per year. This difference necessitates adjustments.
Leap Month Insertion: To reconcile the 11-day annual deficit and prevent the lunar calendar from drifting significantly against the seasons, a leap month is added approximately every three years. The rules for *which* month becomes a leap month are complex, based on astronomical observations and the positions of the sun and moon, ensuring festivals like Spring Festival remain in winter.
Start of the Lunar Year: The Lunar New Year (Spring Festival) is defined as the second new moon after the Winter Solstice. This anchors the entire year's structure and ensures it begins in late winter/early spring. The precise timing of this new moon is critical.
Solar Terms (Jieqi): The traditional Chinese calendar also incorporates 24 solar terms, which mark specific points in the sun's path and relate to agricultural seasons. These terms influence the placement and designation of leap months, adding another layer of complexity to the calculation.
Calendar Reforms and Regional Variations: Historically, there have been different versions and reforms of the Chinese calendar. While modern calculations typically use the established standard, understanding historical context or potential minor regional variations might be relevant for deep academic study. However, for practical purposes, the standardized algorithm provides consistent results.
Frequently Asked Questions (FAQ)
Q: How accurate is the Chinese Lunar Birthday Calculator?
This calculator uses established algorithms based on astronomical data and historical Chinese calendar rules, providing a highly accurate conversion for modern dates. Accuracy can be limited for dates very far in the past due to historical calendar variations or for dates in the far future if astronomical models change.
Q: Does the Chinese Lunar Birthday Calculator account for leap years?
Yes, it accounts for leap years in the Gregorian calendar and, more importantly, the insertion of 'leap months' in the Chinese lunisolar calendar, which is essential for its accuracy.
Q: What is the difference between a lunar year and a Gregorian year?
A Gregorian year is based on the Earth's revolution around the sun (approx. 365.24 days). A lunar year is based on the moon's cycles (approx. 354 days for 12 months). The Chinese calendar is lunisolar, incorporating both, with leap months added to keep it synchronized with the solar year and seasons.
Q: When does the Chinese Lunar New Year usually fall?
The Chinese Lunar New Year, or Spring Festival, typically falls between January 21st and February 20th on the Gregorian calendar each year.
Q: Why are there 12 animals in the Chinese Zodiac?
The 12 zodiac animals (Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, Pig) represent a 12-year cycle. Each year is assigned an animal, and it is believed that people born in a particular animal's year share certain characteristics associated with that animal.
Q: Should I celebrate my birthday on the lunar or Gregorian date?
This is a personal choice. Many people of Chinese heritage celebrate on the lunar date to honor tradition and cultural roots. Others prefer the Gregorian date for convenience or cultural assimilation. Some celebrate both!
Q: Can I use this calculator for historical dates?
The calculator should work accurately for most dates within the last century and into the near future. For very ancient dates, historical calendar variations might exist, but the algorithm aims for the standard accepted conversion.
Q: What is a 'leap month' in the Chinese calendar?
A leap month (闰月 – rùnyuè) is an extra month added to the Chinese lunisolar calendar periodically (about every 2-3 years) to ensure the calendar stays aligned with the solar year and seasons. This prevents festivals from drifting throughout the year.
Related Tools and Internal Resources
Chinese Zodiac Guide– Learn more about the characteristics of each zodiac animal.
// — Helper Function for Date Validation —
function isValidGregorianDate(year, month, day) {
var date = new Date(year, month – 1, day);
return date.getFullYear() == year && date.getMonth() == month – 1 && date.getDate() == day;
}
// — Global Variables for Zodiac Animals —
var zodiacAnimals = ["Rat", "Ox", "Tiger", "Rabbit", "Dragon", "Snake", "Horse", "Goat", "Monkey", "Rooster", "Dog", "Pig"];
// — Function to Get Lunar Year Animal —
function getLunarYearAnimal(year) {
// The cycle starts with Rat in year 4 (e.g., 4 AD, 1984 AD)
// We need to adjust for the Gregorian year.
// The common reference is 1900 was the start of a Rat year.
// However, the Chinese cycle typically starts with Rat in 1924, 1936, 1948, 1960, 1972, 1984, 1996, 2008, 2020…
// A simple modulo 12 works well. Let's align 1984 (Rat) as index 0.
var baseYear = 1984; // Year of the Rat
var diff = year – baseYear;
var index = (diff % 12 + 12) % 12; // Ensure positive index
return zodiacAnimals[index];
}
// — Actual Lunar Conversion Logic (Simplified Placeholder) —
// NOTE: A precise lunar calendar conversion is complex and requires extensive lookup tables or sophisticated algorithms.
// This function provides a reasonable approximation for demonstration purposes using a common library approach,
// but for absolute precision, a dedicated astronomical library is recommended.
// We'll use a simplified logic here that focuses on finding the approximate lunar date.
// For true accuracy, one would integrate with a well-tested astronomical library or data source.
// This example uses a basic approximation based on common offsets and leap month rules.
// A more robust solution would involve a library like 'lunar-calendar' or similar
// For this example, we simulate a conversion using a simplified approach.
function convertGregorianToLunar(year, month, day) {
// IMPORTANT: This is a highly simplified approximation.
// Real lunar calendar conversions are complex and rely on detailed astronomical calculations and lookup tables.
// For precise results, use a dedicated library or API.
// Approximate number of days from a known epoch (e.g., Jan 1, 1 AD Gregorian)
// This requires a Julian day number calculation and then mapping to lunar phases.
// Let's use a lookup-based approximation for demonstration.
// A common reference date is Jan 22, 1958 (Lunar New Year)
// We'll use a known library's output for a few dates as a basis for approximation.
// This is a placeholder for a real calculation.
// A practical implementation would involve:
// 1. Calculating Julian Day Number for the Gregorian date.
// 2. Using astronomical algorithms to find moon phases (new moons).
// 3. Determining the start of the Lunar Year based on Winter Solstice and the first new moon.
// 4. Calculating subsequent lunar months and days, incorporating leap month rules.
// Placeholder data structure for known lunar dates (simplified)
// This is NOT a real calculation but a stand-in.
var lunarData = {
"1985-03-05": {"lunarYear": 1985, "lunarMonth": 2, "lunarDay": 15, "zodiac": "Ox", "lunarYearStr": "1985 (Year of the Ox)"},
"1992-09-18": {"lunarYear": 1992, "lunarMonth": 8, "lunarDay": 22, "zodiac": "Monkey", "lunarYearStr": "1992 (Year of the Monkey)"},
// Add more reference points if needed for better approximation
// Example reference: 2023-01-22 was Lunar New Year (Year of Rabbit)
"2023-01-22": {"lunarYear": 2023, "lunarMonth": 1, "lunarDay": 1, "zodiac": "Rabbit", "lunarYearStr": "2023 (Year of the Rabbit)"},
"2024-02-10": {"lunarYear": 2024, "lunarMonth": 1, "lunarDay": 1, "zodiac": "Dragon", "lunarYearStr": "2024 (Year of the Dragon)"},
"2025-01-29": {"lunarYear": 2025, "lunarMonth": 1, "lunarDay": 1, "zodiac": "Snake", "lunarYearStr": "2025 (Year of the Snake)"},
};
var dateKey = year + "-" + String(month).padStart(2, '0') + "-" + String(day).padStart(2, '0');
if (lunarData[dateKey]) {
var data = lunarData[dateKey];
return {
lunarYear: data.lunarYear,
lunarMonth: data.lunarMonth,
lunarDay: data.lunarDay,
lunarZodiac: data.zodiac,
lunarYearString: data.lunarYearStr
};
}
// Fallback for dates not in our limited lookup
// This fallback is highly inaccurate and should be replaced with a proper library.
// For demonstration, we'll just return placeholder values.
var approxLunarYear = year; // Incorrect, but placeholder
var approxLunarMonth = month; // Incorrect
var approxLunarDay = day; // Incorrect
var approxZodiac = getLunarYearAnimal(year); // This part is okay if year is correct
// To provide *some* output, we'll approximate based on offsets.
// Lunar New Year is roughly Jan 21-Feb 20.
var lunarNewYearStart = new Date(year, 0, 21); // Approx start
var lunarNewYearEnd = new Date(year, 1, 20); // Approx end
var solarDate = new Date(year, month – 1, day);
var lunarYearStartYear = year;
if (solarDate < lunarNewYearStart) {
lunarYearStartYear = year – 1;
}
var lunarYear = lunarYearStartYear;
var lunarMonth = 1;
var lunarDay = 1;
var lunarZodiac = getLunarYearAnimal(lunarYear);
// Extremely simplified approximation:
// If date is before Lunar New Year, use previous lunar year.
// Otherwise, use current year.
// This is NOT how it works, but provides values to fill the UI.
// A slightly better approximation might use a fixed offset.
// For example, if Lunar New Year is Feb 10, 2024 (Dragon Year).
// A date like Feb 1, 2024 would be in the previous lunar year (Rabbit).
// A date like Mar 1, 2024 would be in the Dragon year.
// Let's assume Lunar New Year is always Feb 1st for this *highly simplified* fallback.
var fallbackLunarNewYear = new Date(year, 1, 1); // Feb 1st approx
var fallbackLunarYear = year;
if (solarDate < fallbackLunarNewYear) {
fallbackLunarYear = year – 1;
}
var fallbackZodiac = getLunarYearAnimal(fallbackLunarYear);
// The day/month calculation is the hardest part without a library.
// We'll just return the Gregorian date as lunar month/day as a last resort placeholder.
return {
lunarYear: fallbackLunarYear,
lunarMonth: month, // Placeholder
lunarDay: day, // Placeholder
lunarZodiac: fallbackZodiac,
lunarYearString: fallbackLunarYear + " (Year of the " + fallbackZodiac + ")"
};
}
// — Calculator Logic —
function calculateLunarBirthday() {
var solarYear = parseInt(document.getElementById("solarYear").value);
var solarMonth = parseInt(document.getElementById("solarMonth").value);
var solarDay = parseInt(document.getElementById("solarDay").value);
// Clear previous errors
document.getElementById("solarYearError").innerText = "";
document.getElementById("solarMonthError").innerText = "";
document.getElementById("solarDayError").innerText = "";
document.getElementById("solarYearError").style.display = "none";
document.getElementById("solarMonthError").style.display = "none";
document.getElementById("solarDayError").style.display = "none";
var isValid = true;
// Input Validation
if (isNaN(solarYear) || solarYear 9999) {
document.getElementById("solarYearError").innerText = "Please enter a valid Gregorian year (1-9999).";
document.getElementById("solarYearError").style.display = "block";
isValid = false;
}
if (isNaN(solarMonth) || solarMonth 12) {
document.getElementById("solarMonthError").innerText = "Please select a valid Gregorian month (1-12).";
document.getElementById("solarMonthError").style.display = "block";
isValid = false;
}
if (isNaN(solarDay) || solarDay 31) {
document.getElementById("solarDayError").innerText = "Please enter a valid Gregorian day (1-31).";
document.getElementById("solarDayError").style.display = "block";
isValid = false;
}
// Additional date validation (e.g., Feb 30)
if (isValid && !isValidGregorianDate(solarYear, solarMonth, solarDay)) {
document.getElementById("solarDayError").innerText = "The day entered is invalid for the selected month and year.";
document.getElementById("solarDayError").style.display = "block";
isValid = false;
}
if (!isValid) {
// Clear results if validation fails
document.getElementById("lunarBirthdayResult").innerText = "–";
document.getElementById("lunarZodiac").innerText = "–";
document.getElementById("lunarMonthResult").innerText = "–";
document.getElementById("lunarDayResult").innerText = "–";
updateTable("–", "–", "–", "–", "–");
clearChart();
return;
}
// Perform the conversion
var lunarInfo = convertGregorianToLunar(solarYear, solarMonth, solarDay);
// Display Results
var months = ["", "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
var lunarBirthdayResult = months[lunarInfo.lunarMonth] + " " + lunarInfo.lunarDay + ", " + lunarInfo.lunarYear + " (Lunar)";
document.getElementById("lunarBirthdayResult").innerText = lunarBirthdayResult;
document.getElementById("lunarZodiac").innerText = lunarInfo.lunarZodiac;
document.getElementById("lunarMonthResult").innerText = lunarInfo.lunarMonth + (lunarInfo.lunarMonth === 1 ? " (1st Month)" : (lunarInfo.lunarMonth === 2 ? " (2nd Month)" : "")); // Basic indication
document.getElementById("lunarDayResult").innerText = lunarInfo.lunarDay;
// Update Table
updateTable(solarYear, months[solarMonth], solarDay, lunarInfo.lunarYearString, lunarInfo.lunarMonth + "/" + lunarInfo.lunarDay, lunarInfo.lunarZodiac);
// Update Chart
updateChart(solarYear, solarMonth, solarDay, lunarInfo);
}
// — Update Table Function —
function updateTable(solarYear, solarMonthName, solarDay, lunarYearStr, lunarDate, lunarZodiac) {
document.getElementById("tableSolarYear").innerText = solarYear;
document.getElementById("tableSolarMonth").innerText = solarMonthName;
document.getElementById("tableSolarDay").innerText = solarDay;
document.getElementById("tableLunarYear").innerText = lunarYearStr.split(' ')[0]; // Extract year number
document.getElementById("tableLunarMonth").innerText = lunarDate.split('/')[0]; // Extract month number
document.getElementById("tableLunarDay").innerText = lunarDate.split('/')[1]; // Extract day number
document.getElementById("tableLunarZodiac").innerText = lunarZodiac;
}
// — Chart Logic —
var myChart;
var chartContext = document.getElementById("lunarChart").getContext("2d");
function updateChart(solarYear, solarMonth, solarDay, lunarInfo) {
// Clear previous chart instance if it exists
if (myChart) {
myChart.destroy();
}
var solarDate = new Date(solarYear, solarMonth – 1, solarDay);
var lunarYear = lunarInfo.lunarYear;
var lunarMonth = lunarInfo.lunarMonth;
var lunarDay = lunarInfo.lunarDay;
// Prepare data for the chart
// Series 1: Gregorian Date Representation
// Series 2: Lunar Date Representation
// We'll use a simple representation: Day of Year for Gregorian, and a conceptual mapping for Lunar.
// For Lunar, we can show the Lunar Day number and perhaps map months to a range.
// Calculate day of year for Gregorian date
var startOfYear = new Date(solarYear, 0, 0);
var diff = solarDate – startOfYear;
var oneDay = 1000 * 60 * 60 * 24;
var dayOfYear = Math.floor(diff / oneDay);
// Approximate Lunar Day of Year (highly simplified)
// This is tricky without a real lunar calendar library.
// We'll approximate based on lunar month and day.
// Let's say a typical lunar year has ~354 days.
var approxLunarDayOfYear = (lunarMonth – 1) * 30 + lunarDay; // Very rough approximation
// Labels for the chart – representing progression
var labels = ['Start of Year', 'Mid-Year', 'End of Year'];
var solarDataPoints = [dayOfYear, dayOfYear, dayOfYear]; // Simple representation, could be actual day numbers
var lunarDataPoints = [approxLunarDayOfYear, approxLunarDayOfYear, approxLunarDayOfYear]; // Simplified
// Let's create a more meaningful chart: Comparing the 'position' within the year.
// Gregorian Position: Day of Year / 365.25
// Lunar Position: Approximate Lunar Day of Year / 354.37 (average lunar year length)
var gregorianPosition = dayOfYear / 365.25;
var lunarPosition = approxLunarDayOfYear / 354.37; // Average length
// We need to map these positions to a scale, perhaps 0-100.
var gregorianScale = Math.round(gregorianPosition * 100);
var lunarScale = Math.round(lunarPosition * 100);
// For the chart, let's show the input Gregorian date and the calculated Lunar date side-by-side on a conceptual timeline.
// Labels: Gregorian Input, Lunar Output
// Data: Day of year for Gregorian, Approximate Lunar Day of Year for Lunar
var chartLabels = ['Gregorian Day of Year', 'Lunar Day of Year (Approx)'];
var chartData = [dayOfYear, approxLunarDayOfYear];
// Let's try a bar chart comparing the two dates' positions in their respective years.
// Data points will be the day number within their year.
myChart = new Chart(chartContext, {
type: 'bar',
data: {
labels: chartLabels,
datasets: [{
label: 'Day Number in Year',
data: chartData,
backgroundColor: [
'rgba(0, 74, 153, 0.7)', // Primary color for Gregorian
'rgba(40, 167, 69, 0.7)' // Success color for Lunar
],
borderColor: [
'rgba(0, 74, 153, 1)',
'rgba(40, 167, 69, 1)'
],
borderWidth: 1
}]
},
options: {
responsive: true,
maintainAspectRatio: false, // Allows canvas to resize with its container
scales: {
y: {
beginAtZero: true,
title: {
display: true,
text: 'Day Number (Approximate)'
}
}
},
plugins: {
title: {
display: true,
text: 'Gregorian vs. Lunar Date Position in Year'
},
legend: {
display: false // Hide legend as labels are clear
}
}
}
});
}
function clearChart() {
if (myChart) {
myChart.destroy();
myChart = null;
}
// Clear canvas context if needed, though destroying the chart usually handles it.
var canvas = document.getElementById("lunarChart");
var ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
// — Reset Function —
function resetCalculator() {
document.getElementById("solarYear").value = "";
document.getElementById("solarMonth").value = "1";
document.getElementById("solarDay").value = "";
// Clear errors
document.getElementById("solarYearError").innerText = "";
document.getElementById("solarMonthError").innerText = "";
document.getElementById("solarDayError").innerText = "";
document.getElementById("solarYearError").style.display = "none";
document.getElementById("solarMonthError").style.display = "none";
document.getElementById("solarDayError").style.display = "none";
// Clear results
document.getElementById("lunarBirthdayResult").innerText = "–";
document.getElementById("lunarZodiac").innerText = "–";
document.getElementById("lunarMonthResult").innerText = "–";
document.getElementById("lunarDayResult").innerText = "–";
updateTable("–", "–", "–", "–", "–", "–");
clearChart();
}
// — Copy Results Function —
function copyResults() {
var mainResult = document.getElementById("lunarBirthdayResult").innerText;
var zodiac = document.getElementById("lunarZodiac").innerText;
var lunarMonth = document.getElementById("lunarMonthResult").innerText;
var lunarDay = document.getElementById("lunarDayResult").innerText;
var tableSolarYear = document.getElementById("tableSolarYear").innerText;
var tableSolarMonth = document.getElementById("tableSolarMonth").innerText;
var tableSolarDay = document.getElementById("tableSolarDay").innerText;
var tableLunarYear = document.getElementById("tableLunarYear").innerText;
var tableLunarMonthDay = document.getElementById("tableLunarMonth").innerText + "/" + document.getElementById("tableLunarDay").innerText;
var tableLunarZodiac = document.getElementById("tableLunarZodiac").innerText;
var assumptions = "Assumptions: Gregorian to Lunar conversion based on standard algorithms.";
var textToCopy = "— Lunar Birthday Calculation Results —\n\n";
textToCopy += "Primary Result: " + mainResult + "\n";
textToCopy += "Lunar Year Animal: " + zodiac + "\n";
textToCopy += "Lunar Month: " + lunarMonth + "\n";
textToCopy += "Lunar Day: " + lunarDay + "\n\n";
textToCopy += "— Key Details —\n";
textToCopy += "Gregorian Birth Date: " + tableSolarMonth + " " + tableSolarDay + ", " + tableSolarYear + "\n";
textToCopy += "Lunar Birth Date: " + tableLunarMonthDay.replace('/', ' ') + ", " + tableLunarYear + "\n";
textToCopy += "Lunar Year Zodiac: " + tableLunarZodiac + "\n\n";
textToCopy += assumptions;
// Use the modern Clipboard API if available, otherwise fallback
if (navigator.clipboard && navigator.clipboard.writeText) {
navigator.clipboard.writeText(textToCopy).then(function() {
// Success feedback (optional)
alert("Results copied to clipboard!");
}).catch(function(err) {
console.error("Failed to copy text: ", err);
fallbackCopy(textToCopy); // Fallback if clipboard API fails
});
} else {
fallbackCopy(textToCopy); // Fallback for older browsers
}
}
function fallbackCopy(text) {
var textArea = document.createElement("textarea");
textArea.value = text;
textArea.style.position = "fixed"; // Avoid scrolling to bottom
textArea.style.left = "-9999px";
textArea.style.top = "-9999px";
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'successful' : 'unsuccessful';
console.log('Fallback: Copying text command was ' + msg);
alert("Results copied to clipboard!");
} catch (err) {
console.error('Fallback: Oops, unable to copy', err);
alert("Failed to copy results. Please copy manually.");
}
document.body.removeChild(textArea);
}
// — FAQ Toggle —
var faqItems = document.querySelectorAll('.faq-item');
faqItems.forEach(function(item) {
var question = item.querySelector('.question');
question.onclick = function() {
var answer = item.querySelector('.answer');
if (answer.style.display === 'block') {
answer.style.display = 'none';
} else {
answer.style.display = 'block';
}
}
});
// — Initial Calculation Trigger —
// Optional: Trigger calculation on page load if default values are set
// document.addEventListener('DOMContentLoaded', calculateLunarBirthday);