Bidirectional Gregorian ↔ Chinese lunar converter. Full lunar date (干支), zodiac, 纳音 element. Leap-month aware.
Lunar / Solar Date Converter
How to use
Pick a direction
Toggle "Gregorian → Lunar" or "Lunar → Gregorian". Default is Gregorian-to-Lunar.
Enter a date
Year, month and day as numbers. The range is 1901-01-01 to 2100-12-31, the span of the Hong Kong Observatory's conversion tables. "Today" fills in the current day in Singapore; on the Lunar → Gregorian tab it fills in today's lunar date.
Leap-month checkbox (Lunar → Gregorian only)
The line under the inputs says whether that lunar year has a leap month, and which. The box only converts when that leap month exists; ask for one that does not and the tool names the year's real leap month instead of quietly using the ordinary one.
Read the result
You get the Gregorian date and weekday, the lunar date, the zodiac animal, the year/month/day 干支 and the 纳音, plus any solar term or festival. On a 节 day the 干支 month changes at a set minute, and the result gives that time and both sets of pillars.
The Chinese Lunar Calendar: The Moon Sets the Month, the Sun Sets the Year
The Chinese calendar is lunisolar. Every month starts on the day of a new moon, but the months are numbered by the sun: the month containing the winter solstice is the eleventh, and a month with no major solar term (中气) is the leap month. This tool computes rather than looks up: solar terms from the Sun's apparent longitude, new moons from Meeus, Astronomical Algorithms ch. 49, leap months by the no-major-term rule, with the day boundary at UTC+8, the time the Hong Kong Observatory computes its tables in.
The result was then checked a day at a time against the Hong Kong Observatory's Gregorian-Lunar conversion tables: 73,049 days from 1901 to 2100. They differ on 30 days only, the whole of the fourth month of 1906, whose new moon fell 7 minutes 49 seconds before midnight. The Qing astronomers' computation and the modern one land on opposite sides of midnight, and the tool flags that date.
What's a leap month?
HKO's tables hold 2,473 complete lunar months between 1901 and 2100: 1,312 long months of 30 days and 1,161 short ones of 29, an average of 29.53 days, which is one synodic month. Twelve of them fall about 11 days short of a solar year, so the two centuries carry 73 leap months, about seven in every nineteen years on average, though not on a fixed cycle. Which month repeats depends on which one happens to contain no major term: 2023 has a leap 2nd month, 2025 a leap 6th, 2033 a leap 11th.
干支 (stem-branch), 生肖 (zodiac), 纳音 (sound-element)
There are two year boundaries. The lunar year and its zodiac animal turn at 正月初一 (Chinese New Year): HKO changes the year's 干支 at 00:00 Hong Kong time on 正月初一, and notes that China's 2017 national standard on compiling the calendar (GB/T 33661-2017) agrees. The 干支 calendar's years and months turn at 立春 and at each minor term (节), the reckoning bazi mostly uses. Between the two the years differ: on 10 February 2026, after 立春, the 干支 is 丙午年 庚寅月, while the lunar date is still 乙巳年 腊月廿三. The tool prints both. The 纳音 pairs with the sixty-year cycle, two years to each, so 2026 丙午 and 2027 丁未 are both 天河水 "celestial-river water".
ASEAN Chinese-community uses
Chinese communities in Singapore, Malaysia, Indonesia and the Philippines keep Chinese New Year, the Lantern Festival, Dragon Boat, the Hungry Ghost Festival, Mid-Autumn and Double Ninth by the lunar calendar, so each lands on a different Gregorian date every year. To find a year's Chinese New Year, use Lunar → Gregorian with month 1, day 1; the same tab turns a parent's lunar birthday into a Gregorian one.
The lunar years with two Starts of Spring are exactly the 73 with a leap month
In HKO's tables, of the lunar years 1901 to 2099, 73 contain two Starts of Spring (立春), 73 contain none and 53 contain one. The 73 with two are exactly the 73 thirteen-month years with a leap month.
立春 is not always in the first month: in 103 of the 200 years it falls in the twelfth. In 2026 it fell on 4 February, the 17th of the twelfth month, and Chinese New Year came on 17 February.
The 73 leap months of 1901-2100 fall only in months 2 to 11. Leap 4th and leap 5th months are the commonest (14 each); a leap 9th (2014), leap 10th (1984) and leap 11th (2033) occur once each, and there is no leap 1st or 12th month.
HKO's conversion-table page warns that when a new moon or solar term falls close to midnight its table may be a day out, and names the new moons of 28 September 2057, 4 September 2089 and 7 August 2097. This tool puts all three within 3 minutes before midnight, and flags such dates when you land on one.
Near misses are not rare: of the 2,474 lunar months that begin between 1901 and 2100, 52 start on a new moon less than 15 minutes from midnight.
The winter solstice barely moves on the Gregorian calendar: in HKO's tables it falls between 21 and 23 December every year from 1901 to 2100. The lunar month that contains it is always the eleventh.
The lunar year turns at 正月初一, so a baby born on 15 January 2026 was born on the 27th of the eleventh month of 乙巳 and is a Snake, not a Horse. That date is also before 立春 2026, so the 立春 rule gives the Snake too.
Month lengths do not simply alternate: HKO's tables run up to four 30-day months, or three 29-day months, in a row. "Long and short months alternate" is only an approximation.
The leap 6th month of 2025 began on 25 July and had 29 days. The next leap 6th month is in 2036. How a leap-month birthday is kept varies by family and region; the tool only tells you when the month next comes round.
Before 1929 the tool sets the day boundary at Beijing local mean time (116°25′E), and at UTC+8 from 1929. On that basis all 200 Chinese New Years from 1901 to 2100 agree with HKO's tables.
Frequently Asked Questions
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UTC+8, the time the Hong Kong Observatory computes its tables in, and Beijing local mean time before 1929. Singapore, Malaysia, Hong Kong and Taiwan are all on UTC+8, so their lunar dates are the same. From Europe or the US you still see the UTC+8 lunar date. Vietnam computes its own lunar calendar at UTC+7, which can put a month start on a different day; this tool does not compute the Vietnamese calendar.
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No. The range is 1901-01-01 to 2100-12-31, the two centuries the Hong Kong Observatory tables cover. Outside it there is no published table to check against, and the tool refuses rather than give an unchecked answer. For earlier dates, Academia Sinica's 兩千年中西曆轉換 (sinocal.sinica.edu.tw) reconstructs the historical calendars.
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Custom varies. Common practices: (1) keep the leap month in years that have it and the ordinary month otherwise; (2) always use the ordinary month; (3) celebrate twice in a leap year. The tool does not decide for you: on the Lunar → Gregorian tab, with the leap box ticked, the result lists the next year that has the same leap month.
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Between 立春 and Chinese New Year the two year boundaries give different answers. HKO turns the year at 正月初一; bazi mostly turns it at 立春. The tool prints both, the lunar-year animal first.
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The year pillar turns at 立春, the month pillar at each minor term (节), and the day pillar is the unbroken sixty-day count (1 October 1949 was a 甲子 day). All three follow the same rule, so the year and month always belong together. On a 节 day the month changes at the term's minute, and the result gives that time; the pillars shown are read at noon. An hour pillar needs a birth time, which the Bazi Chart Calculator takes.
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Buddhist and Taoist reckonings are ways of numbering years, each from its own epoch, and many Buddhist and Taoist festivals are kept on lunar months and days. This tool converts between the lunar and Gregorian calendars only; it does not count Buddhist or Taoist years.
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The Chinese zodiac goes by year (a 12-year round); Western star signs go by which of 12 date ranges your Gregorian birthday falls in. The two systems are unrelated.
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No. All conversion happens in your browser; the dates you enter are not sent to any server.
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Compared day by day with HKO's tables for 1901-2100, 30 of 73,049 days differ: the fourth month of 1906, whose new moon fell 7 minutes 49 seconds before midnight. Solar-term dates match HKO for every year from 1914; between 1909 and 1913 six terms are a day apart, each falling minutes before midnight on Beijing local mean time. When a month start or term is close to midnight the result says so.
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Use Lunar → Gregorian and enter year = the target year, month = 1, day = 1; Chinese New Year is 正月初一. For 2027 it is 6 February.
Method & sources
How it computes
Computed, not looked up (LunisolarKernel): solar terms from the Sun's apparent longitude, new moons per Meeus ch. 49, leap months by the no-major-term rule, day boundary UTC+8 (Beijing mean time before 1929). LunarDateViewsKernel adds the refusals and the two year rules: 干支 year and months from 立春 and each 节, lunar year and 生肖 from 正月初一. Checked against every day of HKO's 1901-2100 tables.
What this tool implements
- The Chinese calendar is lunisolar: each month starts on the day of a new moon, and the months are numbered by the sun — the month holding the winter solstice is the eleventh, and a month with no major solar term is the leap month. The page computes this rather than reading a packed table.
- Validated against the Hong Kong Observatory's 公曆與農曆對照表, all 200 yearly files 1901-2100: of the 73,030 days from 1901-01-20 to 2100-12-31, every one agrees except the 30 days of 1906 四月, whose new moon falls 7m49s before midnight on Beijing local mean time; solar-term dates agree for every year from 1914.
- Two year boundaries, both shown. The lunar year and its zodiac animal turn at 正月初一, the rule HKO states for its own tables; the 干支 year and months turn at 立春 and each 节, so the year, month and day pillars printed together always belong together.
- Leap months are handled explicitly rather than silently collapsed into the base month, because 閏四月 and 四月 are different months and a birthday in one is not a birthday in the other. A leap month the year does not have, or a 30th in a 29-day month, is refused with the year's real leap month or the month's length.
- Range 1901-01-01 to 2100-12-31, the span of HKO's tables; outside it the page refuses rather than answer unchecked. Month starts and terms within 15 minutes of midnight are flagged, as HKO itself flags 2057-09-28, 2089-09-04 and 2097-08-07.
- Conversion is deterministic and offline: the same input always returns the same date, and nothing about your dates leaves the browser.
Sources
- Hong Kong Observatory. 公曆與農曆對照表 / Gregorian-Lunar Calendar Conversion Table, 1901-2100, one file per year (all 200 fetched 2026-10-19): https://www.hko.gov.hk/tc/gts/time/conversion.htm — files at https://www.hko.gov.hk/tc/gts/time/calendar/text/files/T{YYYY}c.txt
- Hong Kong Observatory. 今夕是何年？ — "素以正月初一香港標準時間零時零分作為農曆年的干支交替時刻", and that the 2017 national standard 《農曆的編算和頒行》 agrees: https://www.hko.gov.hk/tc/education/astronomy-and-time/time-servi…
- Hong Kong Observatory. 二十四節氣 times (2026 file shown; 立春 04:02): https://www.hko.gov.hk/en/gts/astronomy/data/files/24SolarTerms_2…
- Academia Sinica. 兩千年中西曆轉換 — for dates before 1901, which this page does not convert: https://sinocal.sinica.edu.tw/
What can make this go out of date
- None at runtime: both kernels run in the browser and nothing the reader types is sent anywhere.
Abridged — the full review record for this tool runs longer than the list above.
Pick up where you left off
Stored only in this browser — never sent to our servers.