Dates and Days

Chinese New Year

When Chinese New Year falls, and how firmly

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Ten years, with how close each calculation came to a China-time midnight
YearNew YearAnimalLeap monthClosest call
How this was counted
New Year falls— Animal— Stem— Leap month— From today—

Checked on every build against 17 published New Year dates, 2014 to 2030. How it is checked

Enter a year from 1801 to 2150 for the date of Chinese New Year, its zodiac animal and heavenly stem, any leap month, and the ten years around it. The date follows from four rules about new moons and the winter solstice, reckoned in China Standard Time, and each answer shows how close its calculation came to a China-time midnight.

The four rules

A month begins on the day of a new moon in China Standard Time (UTC+8). The calendar is defined for that meridian, wherever you happen to be. The month containing the winter solstice is always month 11. If thirteen new moons fall between one month 11 and the next, one of those months is a leap month: the first one containing no major solar term. Chinese New Year is the first day of month 1, which is two months after month 11, or three if a leap month has come between.

The animal, the stem and the year’s place in the sixty-year cycle follow by counting. The page computes every date from these rules and has no table of dates to look up.

Why some years cannot be settled here

Each of those rules depends on which calendar day an instant falls on in China. From 1900 to 2100 there are roughly 2,500 new moons and 2,400 major solar terms, so some of them are bound to land within seconds of a China-time midnight. For those, more careful computing does not help: placing the instant on one day or the other is beyond what any finite-precision calculation can settle.

Between 1900 and 2100 this engine finds ten years whose answer rests on a margin too fine for its precision, 2022 among them, and the closest margin is about seven seconds. That is also why the authoritative Chinese calendar is published by an observatory, and why particular years have been argued about in print.

So every answer here shows the margin that decided it. Where the margin is too small, the page still prints the date the arithmetic gives, marks the year as not settled and points you to a published calendar. The New Year dates of the flagged years still agree with the published ones; the flag is about what this calculation can place with certainty.

The leap month, and the 2033 problem

A leap month has no number of its own. It repeats the number of the month before it, so a leap month following the sixth is another sixth month. The solar terms decide which month is doubled, and it changes from year to year: in 2025 the sixth month repeats, in 2028 the fifth and in 2031 the third.

The year that starts at Chinese New Year 2033 has a leap eleventh month, the first since 1645, running from December 2033 into January 2034. Calendars that place leap months by habit, without the solar-term test, get that year wrong, and several published ones did; calendar specialists call it the 2033 problem. It has its own assertion in this site’s test suite.

Questions

When is Chinese New Year?
It falls between 21 January and 21 February, on the first day of month 1. Month 1 starts two new moons after the start of month 11 (the month with the winter solstice in it), or three if a leap month falls between, with each new moon dated in China Standard Time. The calculator above gives the exact date for any year from 1801 to 2150.
Why do some years say the date is not settled?
Because every rule in this calendar turns on which calendar day an instant falls on in China, and over two centuries some of the thousands of new moons and solar terms land within seconds of a China-time midnight. No finite-precision calculation can say which side of midnight such an instant is on. Ten years between 1900 and 2100 are affected, the tightest by about seven seconds. For those years the page shows the computed date and marks it as not settled.
Is Chinese New Year the same as Lunar New Year?
Yes, in ordinary use. Strictly, the Chinese calendar is lunisolar: its months follow the Moon, and its leap months keep it in step with the Sun. A purely lunar calendar such as the Islamic one drifts through the seasons by about eleven days a year. This one adds a leap month roughly seven times in nineteen years, which is why New Year always falls between 21 January and 21 February. Korea and Vietnam observe the same day, though Vietnam occasionally differs because it uses its own meridian.
What decides which month is doubled in a leap year?
The solar terms. In a year with thirteen new moons from one month 11 to the next, the doubled month is the first one with no major solar term in it (a major solar term is the moment the Sun reaches a multiple of thirty degrees of longitude), and it takes the number of the month it follows. Where the solar terms land follows no fixed pattern, so the doubled month moves: 2025 repeats the sixth month, 2028 the fifth, 2031 the third.
What is the 2033 problem?
The name calendar specialists give to the leap eleventh month at the end of 2033, the first since 1645. It belongs to the Chinese year that began on 31 January 2033 and runs into January 2034. Several published calendars got that year wrong: they placed leap months by habit and skipped the no-major-solar-term test. That makes it a good check on any implementation, and this site's test suite asserts it explicitly.