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The Chinese Calendar - Introduction
By: David K. Jordan
IntroductionIn the English-speaking world we use the Gregorian
calendar, a 1582 modification (named after Pope Gregory XIII) of the "Julian"
calendar established by Julius Caesar in ancient Rome. Although many other
calendars have existed through history, and others are used in large parts of
the world today, the Gregorian calendar, complete with months derived from their
Latin names and with its peculiar "rump" month of February, is now the
international standard.
China uses two calendars, one lunar and the other the Gregorian, often
referred to as yin and yang calendars, respectively, or as the "agricultural
calendar" and the "national calendar." There is also a traditional Chinese solar
calendar, different from the Gregorian calendar, as we shall see.
With one exception, all traditional Chinese festivals are based on the lunar
calendar. So traditionally were markets, court sessions, temple fairs, and all
private agreements to meet to do business.
HistoryIn general, a lunar calendar, wherein a month corresponds to the
cycle of phases of the moon, makes sense in a society where there is little
artificial lighting, and the presence or absence of a bright moon makes a big
difference to nocturnal activity (including making it to the outhouse without
mishap!).
On the other hand, a solar calendar, with the year anchored to the solstices
and equinoxes, more realistically reflects our experience with seasons, and
facilitates discussing longer-term historical phenomena (like how old people
are, or when the mortgage will need to be paid off).
By the middle of the 2nd millennium BC, Chinese observers had concluded that
the solar year was pretty nearly 365.25 days long. (The actual length is a hair
shorter, which is why in the international Gregorian calendar, although we
create a Leap Year by adding February 29 in years equally divisible by 4, we
skip Leap Year in centennial years, unless they are equally divisible by 400.)
Each cycle of the moon is very close to 29.5 days long. To accommodate the
half day, some Chinese months are 29 days long and some 30 days long. That part
was easy. The hard part came (as in all calendars) in trying to make lunations
fit the length of the solar year:
1 year = 365 days 12 lunar months = 29.5 x 12 = 354 days (11
days short per year) In other words, there are (365.25 ÷ 29.5 = )
12.3813559322… lunar months per year. That is not a very felicitous number if
you want to make a calendar that fits the movement of both celestial bodies. (In
our own calendar we ignore this problem and let the moon go through its phases
without regard to the days of our artificial "months.")
Since each solar year is about a third of a lunar month longer than 12 lunar
months, one could imagine reducing the error by adding an extra month each third
year:
3 years = 365.25 x 3 days = 1,095.75 days 37 months = 29.5 x 37
= 1091.5 days difference = 4.25 days in three years, 1.4167 days per year)
That is still a relatively large error. The problem was partially
solved, probably by about the Spring & Autumn Period (770-476 BC) by using a
cycle of 19 years, in seven of which intercalary months were inserted:
19 years = 365.25 days = 6,939.75 days (6,935 if one ignores the
quarter days) 19 years x 12 months = 228 months, plus 7 intercalary months
= 235 months 235 months x 29.5 days = 6,932.5 days This still
involved an error of 7.25 days in 19 years, or over a third of a day per year.
The Modern Chinese Lunar CalendarThe modern Chinese lunar calendar,
which seems to have developed sometime in the third century BC, still designates
some months as long (30 days) and some as short (29) days. This it is linked to
the Chinese solar calendar, which of course does not correspond to the Gregorian
calendar. And this brings us to the Chinese solar calendar.
The Chinese solar calendar is based on the movement of the sun over 24 named
points 15 degrees apart on the 360-degree solar ecliptic. (The points are
usually called "solar terms" in English. The names of the terms are given at the
bottom of this page. Each of them falls within a day or two of the same date in
the Gregorian calendar each year.)
Solar movement over the ecliptic is such that the points are 15.2 days apart
(total 364.8 days). Now here is the ingenious part: It takes the sun (15.2 x 2
=) 30.4 days to move from one solar term, across the next, and land on the one
after that. That is slightly longer than a lunar month. Therefore, whereas most
lunar months will contain two solar points, a few lunar months will contain only
one. This triggers the insertion of an immediate additional, "intercalary" lunar
month (rùnyuè 閏月).
Lunar months are numbered rather than named. Although the intercalary month
receives the same number as the preceding month (preceded by the character rùn
閏), no festivals associated with that month are
repeated. Indeed, intercalary months have a reputation for being rather dreary,
since there are no festivals at all associated with them, and some people even
think of them as being generally times of bad luck.)
The effect of inserting the intercalary months based on the error between the
lunar and the solar cycles is to provide a constant correction for the misfit
between the two calendars. This device has kept the lunar calendar reasonably
well linked both to the phases of the moon and to the real solar year for
something over two millennia.
Perhaps because of its associations with the workings of the cosmos,
calculation of the calendar was an imperial government prerogative until the
XXth century, and working it out for yourself and publishing your own calendar
was considered an act of treason.
FestivalsChinese New Year falls on the first day of the first lunar
month. The insertion of intercalary months is the reason why Chinese New Year,
like other traditional Chinese festivals, does not correspond with the same
Gregorian date each year. It is the lunar calendar which determines the
celebration of festival days. Only one significant Chinese festival, "Clear and
Bright" (Qīngmíng 清明), is based on the 24 solar terms.
(For this reason most Chinese pay little or no attention to the solar terms, and
I have heard ignorant Chinese high school students vigorously insist that
Qīngmíng, being traditional, is a lunar festival, even though they are unable to
explain why it never seems to fall on the same lunar date.)
Galloping GregorianizationToday only the Gregorian calendar is official
in China, and Chinese tend to be ambivalent enough about "old fashioned" lunar
dates that they have yet to manufacture, say, a watch that shows lunar as well
as solar dates. During the dark days of the "Cultural Revolution" in China,
published calendars deliberately excluded lunar dates to avoid appearing to
endorse traditional culture. However Chinese around the world continue to
celebrate traditional holidays on the lunar calendar. (In Japan, which borrowed
many of the same festivals from China, they have been shifted to solar dates.)
Historical DatesHistorical dates were (and in Chinese often still are)
normally given as a dynasty name plus reign name plus year within the reign
(counted from the first lunar new year in the reign), followed by the lunar
month and the day of that month:
Qīng 清 dynasty, guāngxù 光緒 reign, 29th year, 6th month 11th day (= 1903 July 24)
(Since all reign names begin on lunar new year, a month or two
after solar new year, Chinese reign years do not perfectly correspond with
Western years, although the error is small enough that it is easily ignored most
of the time.)
In Taiwan the convention of using "reign names" continues, and dates are
normally given in years since the founding of the Republic of China, although
the numbers change on Western new year. (AD 2000 is ROC 89.)
Almanacs and HoroscopesIn addition to solar and lunar calendars,
Chinese tradition provides for the continuous numbering of years, months, and
days using a never-ending cycle of 60 two-character terms, each made of one of
the "Heaven Stems" or "Earth Branches." This numbering naturally blocks years
into cycles of sixty, which are continuously numbered, beginning from 2397 BC.
These designations are not actually used for calendrical purposes, but figure in
calculations of the "astrological" qualities of each day. A separate page of
this web site is devoted to the Heaven Stems and
Earth Branches.
Full article...
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