This converter turns a Western date into its date in the Chinese lunar calendar, with the lunar month and day, the year’s animal and element, the day of the sixty-day cycle and any solar term that falls on it, or turns a lunar date back into the Western date. It covers 1901 to 2074 and works out every month from the Sun and Moon, rather than copying a table.
How it works
The Chinese calendar is lunisolar: its months follow the Moon and its years follow the Sun.
- Months start at the new moon. Each month begins on the day of the new moon, counted in China, and lasts 29 or 30 days.
- The winter solstice fixes the eleventh month. The month that contains the winter solstice is always the eleventh.
- Leap months keep the year in step. Twelve lunar months are about 11 days shorter than a solar year, so about seven years in nineteen have a thirteenth month (63 of the 173 Chinese years from 1901 to 2073). When there are thirteen new moons from one eleventh month to the next, the first month that contains none of the twelve principal solar terms is the leap month, and it repeats the number of the month before it.
- The year is named by the sixty-year cycle of stems and branches, with its animal and element, and begins on the first day of the first month, the lunar new year.
These are the rules of the calendar used in China since 1645, as Helmer Aslaksen sets them out in The Mathematics of the Chinese Calendar (National University of Singapore). Days are counted in China Standard Time (UTC+8) from 1929, and in Beijing local time before that. The new moons and solar terms come from NASA JPL DE440 positions of the Sun and Moon; in our checks, the new moon times agree with the Swiss Ephemeris to within 9 seconds.
Reading the result
For a Western date you get the lunar month and day, the length of that month, the year with its animal and element, the day’s name in the sixty-day cycle, and the solar term if one falls that day, with a table of all the months of that Chinese year. For a lunar date you get the Western date and weekday. If you ask for a leap month that a year does not have, or a 30th day in a 29-day month, the tool says so and names the year’s real leap month.
How we checked it
We converted every day from 1901 to 2074, 63,553 days, and compared it with the Hong Kong Observatory’s Gregorian-Lunar Calendar Conversion Tables. All 174 lunar new year dates agree. The tables begin partway through a month, so for 1 to 19 January 1901 they give the day of the month but not the month; those 19 days agree. Of the other 63,534 days, 63,474 agree. The 60 days that differ are two whole months whose first new moon falls within eight minutes of midnight: in April 1906, where the tables reckon in UTC+8 rather than in Beijing local time, and in September 2057, where the new moon falls less than a minute after midnight. An independent calendar program agrees with us in 2057. When a date you enter is in a month like this, the result says so.
Where traditions differ
The calendar is reckoned in China, so a date in China can be a different date elsewhere, and a calendar reckoned in another time zone can start a month one day apart when a new moon falls near midnight. Before 1929, calendars in China counted days in Beijing local time, as this tool does; some modern tables use UTC+8 for those years too, which is why April 1906 differs.
What it does not do
It does not cover dates before 1901 or after 2074, the range our Sun and Moon data covers with room to spare. It does not list festivals or auspicious days.
Frequently asked questions
↳ What is a leap month in the Chinese calendar?
A thirteenth month added in about seven years out of nineteen, so that the lunar months stay in step with the seasons. It takes the number of the month before it, so a year can have a 6th month and then a leap 6th month.
↳ When does the Chinese year start?
At the lunar new year, the first day of the first month, which from 1901 to 2074 falls between 21 January and 20 February. Ba Zi and feng shui use a different start, Li Chun, around 4 February.
↳ How do I find my lunar birthday?
Enter your date of birth as a Western date. The result gives the lunar month and day, which many families use for birthdays. In later years the same lunar date falls on a different Western date; use the other direction of the converter to find it.
↳ Why do two calendars sometimes disagree by a day?
When a new moon or solar term falls very close to midnight, a few minutes' difference in the time zone used, or in the calculation, moves it to the next day. The converter marks such dates.
↳ Is the date taken as a date in China?
Yes. The Chinese calendar is reckoned in China, so the converter treats the date you enter as a date in China. For a birth abroad close to midnight, the date in China may be different.