Chinese Lunar Calendar Explained

What Is the Chinese Lunar Calendar?

• Type: It is a lunisolar calendar — "luni" because months follow the moon, "solar" because the year adjusts to the sun's cycle using leap months.
• History: The calendar dates back more than 4,000 years and was used by Chinese emperors to schedule agricultural activities, religious ceremonies, and court affairs.
• Official Use: China adopted the Gregorian calendar for official use in 1912, but the lunar calendar remains central to cultural life — holidays, weddings, funerals, and naming ceremonies still follow it.
• Modern Relevance: Today it governs Chinese New Year, Mid-Autumn Festival, Dragon Boat Festival, the zodiac system, and — of course — the Chinese Gender Prediction Chart.

How the Lunar Calendar Works

Moon Phases Drive the Months

• Each month starts on the day of the new moon (when the moon is invisible).
• The full moon falls around the 15th of each month.
• A single lunar month lasts either 29 days (small month) or 30 days (large month).
• The cycle from new moon to new moon averages 29.53 days.

12 Months vs. the Solar Year

• 12 lunar months = approximately 354 days.
• A solar year = approximately 365.25 days.
• The ~11-day shortfall means the lunar calendar would drift through the seasons without correction.
• The fix: a leap month (闰月) is added roughly every 2–3 years, creating a 13-month year.

Leap Months — Keeping Seasons Aligned

• Over a 19-year cycle (called the Metonic cycle), 7 leap months are inserted.
• A leap month takes the number of the month before it — for example, "Leap Month 4" comes after Month 4.
• Leap months are determined by the position of the sun relative to the 24 solar terms (节气).
• Gender Chart Note: If conception falls in a leap month, the chart uses the regular month number, not a special leap entry.

Lunar Age vs. Western Age

• Western age: Starts at 0 at birth. Increases by 1 on each birthday.
• Lunar age (虚岁): Starts at 1 at birth (counting the time in the womb). Increases by 1 at every Chinese New Year, not on the birthday.
• Result: Lunar age is typically 1–2 years higher than Western age.
• Example: Born August 1995, checking in March 2026 → Western age = 30, Lunar age = 32 (start at 1, then +1 for each New Year passed through 2026).
• Why it matters: The Chinese Gender Chart uses lunar age. Using Western age gives the wrong row and wrong prediction.

Chinese New Year Dates

• Chinese New Year is the first day of the first lunar month each year.
• It always falls between January 21 and February 20 on the Gregorian calendar.
• The exact date shifts each year because the lunar and solar calendars don't perfectly align.
• For the Gender Chart: Conceptions before Chinese New Year technically belong to the previous lunar year — this changes both the lunar month and potentially the lunar age.

The 12-Year Zodiac Cycle

• The Chinese zodiac assigns one of 12 animals to each lunar year in a repeating cycle.
• The 12 animals in order: Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, Pig.
• Each animal year is also paired with one of 5 elements (Wood, Fire, Earth, Metal, Water), creating a 60-year grand cycle.
• Zodiac sign is determined by birth year in the lunar calendar — babies born before Chinese New Year carry the previous year's animal.
• Traditional folklore associates personality traits with each animal, though these beliefs have no scientific basis.

The 24 Solar Terms (节气)

• The lunar calendar also tracks 24 solar terms — fixed points in Earth's orbit around the sun.
• Solar terms divide the year into 15-day segments, each marking a seasonal or agricultural milestone.
• Examples: "Spring Begins" (立春, ~Feb 4), "Summer Solstice" (夏至, ~Jun 21), "Autumn Equinox" (秋分, ~Sep 23), "Winter Solstice" (冬至, ~Dec 22).
• Solar terms determine which month gets the leap month — a month without a "major solar term" becomes the leap month.
• Farmers in China still reference solar terms for planting, harvesting, and weather prediction.

Lunar Calendar vs. Gregorian Calendar

How the Lunar Calendar Connects to the Gender Chart

• The chart was built on the lunar calendar — both inputs (age and conception month) must be in lunar terms for the chart to work as intended.
• Lunar age determines the row: Using Western age gives the wrong row and wrong prediction.
• Lunar month determines the column: Plugging in a Gregorian month directly (e.g., "March = 3") ignores the offset between the two calendars.
• Chinese New Year is the pivot point: It resets the lunar year and bumps up the lunar age. Conceptions in January/February may fall in different lunar years depending on the New Year date.
• Leap months are neutral: The chart does not have separate columns for leap months. Use the base month number.
• Our calculator does all of this automatically: Enter your Gregorian dates, and it converts to the correct lunar age and lunar month before looking up the chart.

Frequently Asked Questions