The Chinese Calendar


Rob Stallard introduces the traditional Chinese Calendar system still used for major festivals in Chins (China Eye magazine (2006)).

Determining Chinese New Year and other Festivals

Our events section always lets us know when the next Chinese Festival is due, but have you ever wondered why and how the date changes year by year?

In fact it varies in the same way that Jewish Passover, Christian Easter and Islamic Muharram move around, it is all to do with the moon.

You may also wish to celebrate that 2006 is an unusually long Chinese year as it is 385 days in length (a Chinese year can vary from 353 to 385 days long). The last time this happened was in 1944. It is also a Chinese leap year with a whole extra seventh month.

Before looking at the complicated Chinese Calendar it is worth starting by taking a look at Calendars in general and then the familiar Western system.

Measuring time

Before clocks and watches the only accurate way to measure time was astronomically. The position of the sun, the stars, the moon and the phase of the moon all give information about the date and time. Unfortunately they run on different cycles and can be difficult to measure. In the past when most people lived on the land planting crops and raising stock seasonal variations were key. The best time to plant seed, harvest crops or move stock between pastures was on about the same day each year according to the sun. The easiest universal timepiece to quickly observe is the moon. Because of the motion of the moon about the earth and sun it conveniently passes through four easy to identify phases: new, first quarter, full, last quarter and back to new again. As the moon takes an average 29.53 days to pass through these phases we get a 'month' (yue yue : month in Chinese) for each cycle. Probably related to the moon's phases is the derivation of a 'week', it is roughly one phase of the moon. It's then easy just to count the days within a phase. So you can give someone a meaningful relative date - three days after the third full moon. The Romans used a strange system of Calends, Nones, and Ides for denoting the day within a month. The very name 'Calendar' is derived from 'Calends' referring to the way that the Roman astronomer would 'proclaim' [kalendae] the new moon at the start of a month.

The sun and moon cycles are not synchronised and even worse one annual trip around the sun is not a whole number of days (on average 365.2425) so you can not just count days and lunar months to get to the same date in the year.

If you are a farmer you need to know the 'solar' time but can only easily count the passage of days by the moon-'lunar' time. This dilemma has led to the invention of a rich and ingenious range of calendar systems that have been used over the centuries.

The Western Calendar

To cope with the awkwardness of the odd fraction of a day left over each year (0.2425 of a day or 5.8 hours), the first Roman Emperor Julius Caesar introduced an average year length of 365.25 day year in 46BCE. He did this by adding a leap day at the end of every fourth year in February. Note that the ancient Romans started the year with the month of March with the Spring Equinox and had ten months (hence our October meaning 8th but now the 10th month; November meaning 9 and December meaning 10).

The Julian adjustment helps but there is still a discrepancy to the true solar year length of 10.8 minutes per year (or 0.0075 days per year). This added up over centuries and the Gregorian calendar was introduced by Pope Gregory in 1582 to take out the accumulated discrepancy, which by then had added up to ten whole days. As well as 'removing' the ten days, he stopped the same error happening in future by adding a new rule that century years are not leap years but years divisible by 400 are still leap years. As Europe was in the throws of Reformation only the Roman Catholic countries adopted this strange papal invention. In the U.K. it was not until 1752 that the Gregorian calendar was finally adopted. Despite a widespread campaign to 'give us back our 11 days' (by this time the true solar year was out by 11 days) the change took place and there was no longer an excuse for complete confusion when comparing dates over Europe. The Eastern Orthodox Church has yet to make the change.

Incidentally, have you ever wondered why the end of the UK tax year is April 5th rather than something sensible like December 31st? Well, firstly the original tax year followed the ancient Roman tradition of beginning the year with Spring, actually on the first Quarter day or Lady Day on March 25th. Secondly to get around people's legitimate objection in 1752 that they would have been taxed for the 11 days that the government wanted to arbitrarily remove from history, the tax year was moved 11 days forwards into the new year.

Lunar adjustments

The main religions all have festivals tied to the moon which is not related to the solar year, reflecting the fact that dates were originally recorded in terms like 'four days after the third new moon of the year'. To work out when a festival should occur in any year observations are made of the moon relative to the sun so that the two systems are synchronised for the year.

In the Christian year some feasts stay put including Christmas; All Souls Day and saint's days while others change - they are the movable feasts (e.g. Palm Sunday, Easter, Ascension Day, Whit Sunday) that are tied to the moon. The James I 'Book of Common Prayer' has some interesting looking tables and algorithms for calculating on which day in any year Easter will fall. Ideal for reading during very boring sermons. Here is one rule:

“To find the Golden Number, or Prime, add one to the Year of our Lord, and then divide by 19; the remainder, if any, is the Golden Number; but if nothing remaineth, then 19 is the Golden Number.
To find the Dominical or Sunday Letter, according to the Calendar, until the Year 2099 inclusive, add to the Year of our Lord its Fourth Part, omitting Fractions; and also the Number 6: Divide the sum by 7; and if there is no remainder, then A is the Sunday Letter: But if any number remaineth, then the Letter standing against that number in the small annexed Table is the Sunday Letter.”

You may notice the use of the number 19, this is no metaphysical mumbo-jumbo, it reflects the fact that 19 x 365.25 (19 years) = 6939.75 days is very, very close to 235 lunar months (235 x 29.53 = 6939.55 days) so the Easter and Chinese Calendars repeat themselves every 19 years. This is the Metonic Cycle, which is named after the ancient Athenian Meton who discovered it in the fifth century BC (although this knowledge could easily have made its way from China).

There is another way to adjust the years and months so that they remain in rough synchronization without using leap days and that is to every few years introduce a whole new 'leap' month. Each year there will be a slight discrepancy between true solar time using this system and to achieve the best match the leap month is introduced between different months in the year. This is the basis of the traditional Chinese Calendar.

Chinese Calendars

Ancient Star Observatory
The Tower of Guo Shoujing is an impressive
astronomical instrument dating from 1276AD
capable of making measurements to
five decimal places.

There is not just one but at least two Calendar systems that often get confused. The systems are best differentiated by their names : sui and nian. The sui sui : year year is a solar year defined from one position of the sun from one year to the next and was used in agriculture. The nian nian : year year is the complex lunar-solar year used for official records and festivals. The sui year has an average length of 365.2425 days to match the true solar year while the nian year varies in length according to the moon. There is also the lichun calendar that runs from the beginning of Spring to the following Spring and is also a true solar year, this calendar is used in Chinese astrology and will therefore be out of step with the nian calendar. The fact that 'sui' is used to ask people their age in Chinese indicates its long standing association with calendars even though 'nian' is the character for a year.

The 'nian' calendar used today is more or less that devised by Emperor Wu of the Han dynasty in 104BCE which pre-dates and is more accurate than the Julian system.

Ancient Chinese Calendars

The use of a linear year number (e.g. 2006) is a Western (chiefly Christian) invention. Throughout the entire span of Imperial China dates were defined by the year number of the current Emperor's reign. This is not unique to China, the system was used to some extent in UK too, chiefly in medieval official documents. For example, the sixteenth year of Henry VIII reign would be written as '16 Henry VIII' representing 1509 + 16 = 1525.

To denote the year of the reign the Chinese did not use the standard decimal numbers, they used a special cycle of sixty years divided into five groups of twelve years. Except for the Emperor Kangxi (1661-1722) no emperor has reigned over 60 years so this system of nianhao (reign names) worked well. Traditionally a Chinese lifetime was 60 years unlike the Western three score and ten - 70 years. To shake off bad luck or mark significant events more than one 'reign name' was occasionally used during an emperor's reign.

It is from the special use of stems and branches that we find the familiar Chinese astrological cycle of twelve animals representing twelve years.

The Ten Heavenly Stems (tian gan heavenly stems) - also the Chinese 'Elements'


The Twelve Earthly Branches (di zhi earthly branches) - also the Chinese Zodiacal Years


To denote a number with stems and branches we always use a pair of stem and branch characters. To count both the stem and branch are advanced by one each time.
Year 1 : 1,1 jia zi [jiazi];
Year 2 : 2,2 yi chou [yichou];
Year 3 : 3,3 bing yin ... ...
Year 10 : 10,10 gui you but then ...
Year 11 : 1,11 jia xu;
Year 12 : 2,12 yi hai;
Year 13 : 3,1 bing zi ... leading eventually to
Year 60 : 10,12 gui hai [guihai]
And then the cycle repeats itself with 1,1

Most Westerners only work with the 'branch' part of the year of birth, while in fact the stem should be taken into account as well. The year 2000 was a 'metal' stem, 'dragon' branch year or golden dragon year - very propitious.

The use of this system for counting days goes back to the Shang Dynasty (1600-1046 BCE). Indeed because the oracle bones are the best preserved of ancient Chinese writings the branch and stem characters are the most frequently written characters at the time. The counting system was used not just for years but months, days and hours as well. A Chinese horoscope uses these four numbers (or pillars zhu zhu : pillar) to represent the date and time of birth in the sui Calendar.

It is believed that the use of ten stems may represent the ten day week that was used in China up to the Song Dynasty (960-1279). The Chinese month of 29/30 days can conveniently be split into 3 ten day weeks. [Napolean had an unsuccessful attempt to introduce a ten day week but that lasted only from 1793 to 1806].

The origins of sexagenary cycle of 60 go back into the mists of time, we still use it for minutes, seconds and trigonometric angles. The link to calendars may relate to the fact that six cycles are 360 (nearly a solar year in days) and one cycle is roughly two lunar cycles.

The numbering system isn't much to do with calendars other than a special way to record dates and times in Chinese.

Chinese Months

The nian calendar is split up into months depending on the moon. Each month starts with a New Moon. To be unambiguous you have to define when and where the New Moon is observed. This is currently defined to be at the 120° longitude from Greenwich and the day starts at midnight at this longitude. The day number within the month is then counted and due to the awkward fraction of 0.53 day for a month's average length it can have 29 days (xiao yue xiao : smallyue : month small month) or 30 days (da yue da : largeyue : month big month). Each month may vary in length from year to year as to how many days it has just because of the time of day of the new moon that defines it started. If the new moon occurs late in the day then it is likely to have 30, if early then 29. Mathematicians might then think that this will tend to give alternations of month lengths 29;30;29;30 to achieve the average of 29.53 for a lunar orbit. However since 619 in the Tang Dynasty the orbit of the moon is corrected for things like the Moon's perigee and this leads to occasional sequences of long months e.g. 30; 30; 30 or short months 29; 29; 29.

The lichun (solar) calendar is traditionally divided into 24 named periods (jieqi jieqi) of about 15 days each. These fall on about the same date in the Gregorian calendar give or take a day. This is because the Gregorian system can be out due to the effects of leap day insertion and motion of perihelion (small perturbation of the Earth's orbit). The names of the Jieqi reflect their use as the farmer's calendar. It is ancient, dating from at least the Zhou dynasty (1122-221 BCE) and the jieqi names were more usually used rather than the month names in the year.

Chinese NameJieqiRough Gregorian dateNameMonth name
Li chun lichunFebruary 4Beginning of springTiger; First
Yu shui yushuiFebruary 19Rain water
Jing zhejingzheMarch 6Waking of insectsRabbit; Apricot
Chun fenchunfenMarch 21March equinox
Qing mingqingmingApril 5Pure brightnessDragon; Peach
Gu yuguyuApril 20Grain rain
Li xialixiaMay 6Beginning of summerSnake; Plum
Xiao manxiaomanMay 21Grain full
Mang zhongmangzhongJune 6Grain in earHorse; Guava/ Pomegranate
Xia zhi xiazhiJune 22June solstice
Xiao shuxiaoshuJuly 7Slight heatSheep; Lotus
Da shudashuJuly 23Great heat
Li qiuliqiuAugust 8Beginning of autumnMonkey; Orchid
Chu shuchushuAugust 23Limit of heat
Bai lubailuSeptember 8White dewChicken; Osmanthus
Qiu fenqiufenSeptember 23September equinox
Han luhanluOctober 8Cold dewDog; Chrysanthemum
Shuang jiangshuangjiangOctober 24Descent of frost
Li donglidongNovember 8Beginning of winterPig; Good
Xiao xuexiaoxueNovember 22Slight snow
Da xuedaxueDecember 7Great snowRat; Winter
Dong zhidongzhiDecember 22December solstice
Xiao hanxiaohanJanuary 6Slight coldOx/Cow; Last
Da handahanJanuary 20Great cold

The start of the lichun year is defined to be midway between the Mid Winter Solstice and Spring Equinox, this is the 'farmer's year' beginning with Spring that marks the new year just like the ancient Roman system. Remember that the 'sui' year is the same except that it starts at the Mid Winter Solstice : dongzhi.

Chinese New Year

Each Chinese month matches a lunar orbit starting at a new moon, and so the start of the year is on the first new moon of the year.

Chinese New Year (CNY) or Spring Festival (chun jie Chun Jie) can fall on a day ranging between January 20th to February 21st, however the extreme dates are rather rare, the next year that CNY falls on February 21st is 2319. This is just like Easter falling very late or very early. Another name for CNY is nong li xin nian nong li xin nian (literally 'lunar calendar' new year), you may also note that the name includes the 'nong' character representing 'agriculture' so this tells you something about its origins in the 'sui' year.

One of the simplest ways to approximately calculate the date of Chinese New Year is to tie it in with the sui calendar and put it on the day of the new moon closest to (before or after) the first jieqi - lichun the beginning of the sui year. Alternatively CNY usually falls on the second new moon from the Winter Solstice (December 22nd). Neither of these is 100% reliable when CNY is very early or very late as there are small corrections to be made which only astronomers and mathematicians will appreciate.

Leap months

In a Chinese leap year with a whole extra month there may be two occurrences of the 'solar' defined start of Spring lichun, these years are called double spring 'shuang chun' years. For the same reason a short normal year can just miss the start of Spring and are called 'blind years'.

The Chinese nian calendar adds a whole leap month ('run yue') making a double month rather than a 'leap day' to re-synchronize the solar year with the lunar year every two or three years. The place that the month is inserted varies from year to year. In the Chinese calendar for 2006 the seventh month 'qi yue' is followed by the intercalary seventh month 'qi run yue'.

The choice of place for the leap month is such that the 'solar' based system is keyed in again. A leap month has no 'Solar Centre Point'. This can be worked out from the position of the sun in the zodiac during a lunar month. It is extremely unlikely that the leap month occurs in the first or twelfth months, it usually occurs somewhere between the third and the seventh months. The occurrence of the leap month 'roughly' follows the 19 year Metonic cycle so the 4th month is followed by a leap month in 2001, and also 4th month in 2020; 5th is the leap month for 2009 followed by 5th month in 2028. However our current 7th leap month in 2006 is followed by 6th leap month in 2025, so it's not a rule but a rough guide.

According to tradition a double eighth month makes the year unlucky, strange because 8 is a lucky number in China. (You may have noticed that the Olympics in Beijing began at 8pm on August 8th 2008.) The unlucky nature of double August gained strength with the death of Chairman Mao on September 9th 1976 and the massive Tangshan earthquake on July 28th 1976 which left at least 255,000 people dead (very close to the numbers killed in the Indonesian tsunami). In 1995, the following year with a double 8 month, saw major floods in Central China and an earthquake in SW China but thankfully less loss of life. The next double eight leap year is some time off, it is not 2014 as some web sites claim, but is 2052.

With the rule for months and insertion of leap months the total length of a Chinese 'nian' year varies between 353 and 385. Most normal years are 354 days long and most leap years are 384 days long.

A 353 day year occurs with 5 months of 30 days and 7 months of 29 days. A 383 day year occurs in leap years with 6 months of 30 days and 7 months of 29 days. A 385 day year (as in 2006) occurs in leap years with 8 months of 30 days and 5 months of 29 days

Because the 'sui' year is tied to the solar year it can only be either 365 or 366 days long.

Other Festivals

Just like in the Christian calendar some festivals are 'movable' (timed to the lunar cycle) and some fixed to the solar 'sui' calendar. Because the Chinese solar year is different to the Gregorian solar calendar even the fixed dates for festivals may vary by a day or two each year.

Qingming is fixed in the sui/lichun calendar (April 4th to 6th) and it may be in the 2nd or 3rd Chinese month

The Dragon Boat Festival is on the 5th day of the 5th Chinese lunar month

Mid Autumn Festival is on the 15th day of the 8th Chinese lunar month.

The Double Ninth Festival is on the 9th day of the 9th Chinese lunar month

Dongzhi is the mid Winter solstice (December 21st to 23rd) and is fixed in the sui/lichun calendar

Astronomical Measurements

In the Ptolemaic view of the Universe everything in the skies should be fitted to nice perfect circles with regular, unchanging cycles.

In the West it was not until Galileo, Kepler and Copernicus that this view was seriously challenged. The Chinese knew this far earlier, using very accurate measurements over long periods of time they realised that the heavens didn't quite behave themselves. The effects that we only relatively recently fully understand include the wobble of the Earth on its axis and also the elliptic orbit rather than circular orbit of the planets and the moon. Calendars make use of an average lunar month and an average solar year to approximate these deviations from 'perfection'.

Long before the invention of the telescope by Galileo in 1609 the Chinese were making astronomical observations and measurements. One of the important types of astronomical instruments in China was the gnomon. A gnomon in its simplest form is just a vertical stick with which you measure the length of the shadow cast by the sun or moon. By careful measurement every day over the year you can determine mid Winter and mid Summer.

The most famous and largest instrument of this type is the Tower of Guo Shoujing at Dengfeng, Henan. It is an impressive astronomical instrument built in 1276. It used a cross-hair and water (to maintain an accurate level) so that the motions of the heavens could be measured to five decimal places. A feat not achieved in Europe for another five hundred years.

In China, the Emperor was the link between the heavens and mankind, his subjects. If some strange astronomical event took place, especially solar eclipses, then this was generally bad news signalling that the heavens no longer supported him and his dynasty. Calculating the occurrence of a solar eclipse requires the accurate prediction of the positions of the sun and the moon. If an emperor has fore-knowledge of these events he can use 'political spin' to blame the eclipse on other factors or people and not himself.

To keep the calendar accurate they needed to account for the slight perturbations of the Earth and moon. For example we think of the September equinox as fixed on September 22nd but it can occur between September 21st and 24th. So the Chinese astronomers use adjusted positions for the sun and moon in calendar calculations rather than their perceived position and it is this that leads to discrepancies from what is actually seen from the Earth.

The golden age of Chinese astronomy was probably during the Song dynasty (960-1279) after that time the knowledge of how to compute and adjust calendars was lost until the coming of Europeans reinvigorated astronomical science in China.

Western Adjustments

When I first came across the story of European contacts with China it was the story of the Jesuit priests (chiefly Matteo Ricci in 1582) that inspired me rather than Marco Polo. The Jesuits used their knowledge of Western science - particularly astronomy and geometry to gain power and influence with the Ming emperors. They even translated the ancient Greek classics of Euclid into Chinese, and it is this trigonometric knowledge that was a key to their acceptance at court by the Emperor.

The Chinese had by this time 'forgotten' the way of making calculations for making accurate astronomical observations and also using these observations to make predictions of the occurrences of eclipses and the computation of year lengths. The acceptance of the Jesuits was in good part down to the accurate prediction of the solar eclipse on June 21st 1629. This resulted in the adoption of adjustments suggested by the Jesuits to the Chinese Calendar in 1645. The fate of the Jesuits was not a happy one as by 1665 despite further astonishingly accurate predictions, the 'conservative' Chinese astrologers/astronomers conspired to get Adam Schall arrested and he died under house arrest in the following year.

Modern China

When the Qing Empire fell in 1911 the Nationalist government overturned centuries of tradition by adopting the Western Calendar. The Gregorian Calendar came in with the bland numbering of days and months that we now see on all official Chinese publications.

The year number starting from the 'mythical' Yellow Emperor was also instituted at about this time. The year 2698 BCE is therefore treated as the base date. According to this reckoning 2006 is the year would be 4703 (except days before the CNY on January 29th). Before the founding of the Republic only the emperor name and reign year had been used.

The Civil War in China affected the Chinese Calendar. In 1928 the time zone for China was set at 120° longitude to more closely match the location of the new Nationalist capital at Nanjing rather than Beijing. It is the Purple Mountain Astronomical Institute at Nanjing that is still used as the calendar setting for China. However, the Nationalists in Taiwan and British subjects in Hong Kong continued to use the calendar tables for the old Imperial time zone for the Beijing meridian. So between 1929 and 1978 there is a discrepancy of 14 minutes (the difference in longitude between Beijing and Nanjing) in the calendar which led to some confusion culminating in the celebration of Mid-Autumn Festival in 1978 on different days. Thankfully the Nanjing system is now used everywhere.

New Years

YearChinese New Year dateDouble or leap monthCycle yearYear cycle nameYear cycle name
2000Sat February 5th 78,17geng chenMetal/Dragon
2001Wed January 24thfourth month78,18xin siMetal/Snake
2002Tue February 12th 78,19ren wuWater/Horse
2003Sat February 1st 78,20gui weiWater/Sheep
2004Thu January 22nd second month78,21jia shenWood/Monkey
2005Wed February 9th 78,22yi youWood/Rooster
2006Sun January 29thseventh month78,23bing xuFire/Dog
2007Sun February 18th78,24ding haiFire/Pig
2008Thu February 7th 78,25wu ziEarth/Rat
2009Mon January 26thfifth month78,26ji chouEarth/Ox
2010Sun February 14th78,27geng yinMetal/Tiger
2011Thu February 3rd78,28xin maoMetal/Rabbit
2012Mon January 23rdfourth month78,29ren chenWater/Dragon
2013Sun February 10th 78,30gui siWater/Snake
2014Fri January 31st ninth month78,31jia wuWood/Horse
2015Thu February 19th 78,32yi weiWood/Sheep
2016Mon February 8th 78,33bing shenFire/Monkey
2017Sat January 28thsixth month78,34ding youFire/Rooster


There are a number of web sites that give some information on the Chinese Calendar including:
Chinese Calendar
Here is a web site with a month in view and daily calendar information:
Detailed calendar information
The wikipedia entry is comprehensive but has a few minor errors in it :
Wikipedia Entry
A Chinese calendar with relevant on this day and a full year print-out:
On this day with Chinese calendar I have summarised some detailed analysis data from a long and authoritative 'academic' article on the subject:
Academic Analysis
For more on Calendars in general (there are others that are equally strange) try:
Assorted Calendars
Joseph Needham's 'Science and Civilization in China' is remarkably quiet on Calendars but has a long section on astronomy and the jieqi.
You can download a 'free' Chinese calendar program from here and it seems to be accurate:
Lunar Calendar Calculator

© Copyright Society for Anglo-Chinese Understanding (SACU) China Eye magazine Summer 2006

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