Lunar Calendar Conversion Tool
Convert between solar and lunar calendar, check zodiac, solar terms, traditional festivals
Enter Solar Date
Enter Lunar Date
What is the Lunar Calendar?
The Chinese lunar calendar, also known as the agricultural calendar, is a traditional Chinese calendar system. It is a lunisolar calendar that uses the lunar phase cycle (synodic month) for months while also accounting for the solar year, adding leap months to reconcile the two. The difference between the lunar and solar calendars: the solar calendar is purely based on Earth's orbit around the Sun; the lunar calendar is lunisolar, considering both moon phases and seasonal changes. Traditional Chinese festivals such as Spring Festival, Mid-Autumn Festival, and Dragon Boat Festival follow the lunar calendar.
How to Use
Solar to Lunar
- Select the 'Solar to Lunar' tab
- Enter year, month, and day, or click 'Use Today' to fill in the current date
- Click the 'Convert to Lunar' button
- View results including lunar date, zodiac, Gan-Zhi year, solar terms, and festivals
Lunar to Solar
- Select the 'Lunar to Solar' tab
- Enter the lunar year, select month and day (leap months are available)
- Click the 'Convert to Solar' button
- View the converted solar date and details
Calendar Tips
- When converting birthdays or festival dates, confirm whether the source date is Gregorian or lunar before entering it.
- Leap lunar months are different from normal months with the same number; choose the leap-month option only when the original date explicitly uses it.
Use Cases
Technical Principle
The lunar calendar is a lunisolar system: months follow the synodic month (29.53 days on average) and the year length is nudged toward the tropical year (about 365.24 days) via leap months. A normal lunar year has only 12 synodic months, about 354 days - 11 days short of the tropical year. Without adjustment, Spring Festival would gradually drift into summer over time. To keep the lunar year aligned with the seasons, the traditional rule is '7 leap months in 19 years': 19 lunar years total about 6939.6 days, very close to 19 tropical years at 6939.5 days. Whether a given year has a leap month, and which month it is, is decided by the 'no-zhongqi leap month' rule: a month that contains none of the 12 zhongqi (Vernal Equinox, Summer Solstice, Autumnal Equinox, Winter Solstice, ...) is designated the leap month, written as 'leap Xth month'. The 24 solar terms are defined by the Sun's apparent position along the ecliptic, one every 15 degrees. Their solar dates only swing by 1-2 days each year, so Qingming lands on April 4 or 5; their lunar positions drift with the leap month rules. In practice, synodic month length and solar term moments both require precise astronomical calculation, so most tools precompute a lookup table for 1900-2100 (the first day of each lunar month in solar dates, which years have leap months, and which month) and do a table lookup at runtime instead of running astronomy in the browser. Outside this range, the result is no longer guaranteed to be accurate.
- The lunar calendar is lunisolar: months track moon phases, year length is kept in sync with the tropical year via leap months - fundamentally different from the purely solar civil calendar.
- A synodic month averages 29.53 days; lunar months come in 30-day long months and 29-day short months depending on the actual moon phase, not a fixed rule.
- Uses the '7 leap months in 19 years' rule, with the specific leap month chosen by the no-zhongqi rule; leap months are not pinned to any particular month.
- The 24 solar terms are spaced every 15 degrees of solar longitude; they are nearly fixed on the solar calendar and drift on the lunar calendar.
- The tool is based on a precomputed astronomical table for 1900-2100; dates outside this range may have conversion errors.
- The 60-year Gan-Zhi cycle and the zodiac (lunar new year on the 1st of the first lunar month) define year boundaries; people born across the new year should be assigned the zodiac by the Spring Festival date.
Examples
Spring Festival Date Lookup
Lunar 2027, 1st month, 1st day
-> Solar 2027-02-06 (Saturday)
-> Gan-Zhi Dingwei Year, zodiac Goat/SheepBirthday Solar to Lunar
Solar 1995-08-20
-> Lunar Yihai Year, 7th month, 25th day
-> Gan-Zhi Yihai Year, zodiac Pig
-> Solar term: around Chushu (End of Heat)Leap Month Year Lookup
2025 has a leap 6th month; 2028 has a leap 5th month
-> Leap years have 13 lunar months, about 384 days
-> A leap-month birthday only comes around every ~19 yearsFAQ
What does the lunar calendar show?
The Chinese lunisolar calendar with the corresponding Gregorian date, month phase (e.g. 正月初一), zodiac year, heavenly stem and earthly branch, solar terms (24 节气), traditional festivals, and lucky/unlucky activities for the day - the kind of information found on a printed paper huangli (黄历).
Why does Chinese New Year fall on a different Gregorian date each year?
Chinese New Year is the new moon closest to the Lichun (start of spring) solar term, falling between Jan 21 and Feb 20. The lunar month is about 29.5 days, the solar year about 365.24 days, so a leap month is added every 2-3 years to keep the calendar aligned with the seasons.
What is a leap month (闰月)?
A 13th month inserted to keep the lunisolar calendar in sync with the solar year. The leap month repeats the previous month's name (e.g. 闰四月 follows 四月). Birthdays falling in a leap month are usually celebrated in the next non-leap occurrence of that month.
Are the 24 solar terms shown?
Yes. The 24 solar terms (二十四节气) divide the solar year into 15° increments along the ecliptic. They drive farming, food, and traditional medicine timing - 立春, 雨水, 惊蛰 and so on. The page shows the term for the current day or the next upcoming term.
Are the 'auspicious activities' real or for fun?
They come from the traditional almanac (黄历), which lists activities (marriage, moving house, opening a store, surgery) considered favourable or inauspicious for each day based on the cyclical stem-branch system. Take it as cultural reference; modern decisions don't need to follow it.
How far back and forward does it work?
The page typically covers 1900-2100, which covers all common use cases (calculating an elder's lunar birthday, future festivals, family records). Outside that range the underlying tables may be unavailable.
Is the conversion done in my browser?
Yes. The Gregorian-to-lunar mapping uses a built-in lookup table; nothing is uploaded. The calculation works offline once the page is loaded.