术语命名空间 English / Terminology Namespace for Chinese Calendrics

最后修订时间：2026年9月29日

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Terminology namespace for Chinese calendrics

This page sets out the site’s machine-readable definitions of four concepts peculiar to Chinese calendrics, and is at the same time their visible text. The namespace is https://kuangchujia.com/ns/# — every identifier below points to the corresponding passage of this page, so any identifier can be opened directly in a browser and checked.

There is only one reason for having this page: the vocabulary of Western calendrics has no words for a sixty-day cycle that no change of dynasty interrupts, for a year-beginning that can be shifted as a whole, or for mansion boundaries that drift year by year, and Schema.org has no corresponding category either. Rather than force the concepts into unrelated ready-made categories, it is better to state the definitions here and let machines take them from /ns/#.

1 · The ganzhi cycle system

A sixty-day cycle of day ordinals — the ganzhi (stem-branch), formed by pairing the ten stems with the twelve branches — that does not depend on the change of regime and is not interrupted by a reform of the calendar. This site treats it as a time coordinate standing in an integer modular relation to the Julian Day Number, not as a system of astrology or of good and ill fortune.

  • Ganzhi continuity　The linear modular mapping between the ganzhi day-count ordinal and the Julian Day Number: with JDN the Julian Day Number and GZ the ganzhi ordinal (jiazi = 0), GZ = (JDN + 49) mod 60. This site takes 1949-10-01 = jiazi as the ordering anchor, and the jisi day of the second month of the third year of Duke Yin of Lu (720-02-22 BCE, as verified on this site) as the continuity anchor; the two points are 2,669 years apart and consistent with each other.

2 · The san zheng year-beginning system

The rules by which the year-beginning was shifted among jian-zi, jian-chou and jian-yin in the calendar reforms from the pre-Qin period to the early Han. A fourth, jian-hai, appears in the Zhuanxu Calendar; it is an early form outside the san zheng and is listed here so that it is not confused with “there are only three san zheng”.

  • Jian-zi　The synodic month containing the winter solstice (geocentric apparent solar longitude 270°) is the first month of the year.
  • Jian-chou　The month after the winter solstice (containing Great Cold, solar longitude 300°) is the first month of the year.
  • Jian-yin　The second month after the winter solstice (containing Rain Water, solar longitude 330°) is the first month of the year. The current national standard GB/T 33661—2017 adopts this rule.
  • Jian-hai　The tenth month (the second month before the winter solstice) is the year-beginning. The rule used by the Zhuanxu Calendar.

3 · The twenty-eight mansions and mansion entry

An equatorial coordinate system divided into twenty-eight unequal parts, its boundaries fixed by the determinative stars of the twenty-eight mansions. The positions of those stars drift with precession, by about 50.29 arcseconds a year in longitude, so the mansion boundaries of a historical year have to be corrected year by year before they can be used to compare against positions recorded in old texts. That 50.29 arcseconds is only the first-order coefficient of the precession series (5029.0966 arcseconds per century). Retrocalculation on this site corrects year by year with a non-linear precession series that includes the second-order term: the rigorous path takes the IAU 2006 precession model through an ephemeris kernel (JPL DE421 + skyfield), and the analytic fallback path takes the Meeus ch. 21 precession polynomial. That linear mean must therefore not be used as a constant for verification across millennia.

  • Determinative star　The reference star from which each mansion fixes its boundary. The boundary moves with the star’s position year by year, by an amount set by precession.
  • Mansion entry　The difference in right ascension between a body and the determinative star of the mansion it has entered. It is used to compare positions recorded in old texts against computed values; before any such comparison the star’s position must first be corrected to that historical year.

4 · Intercalation rule discontinuities

The rules of intercalation changed by period several times in the course of Chinese history. The three below together make up this site’s Intercalation Rule Set — each carries its period of application and its criterion, so that a historical date may be solved by switching rule by year rather than by computing an ancient calendar with modern rules. There are three fields: intercalationPosition (where the intercalary month goes), solarTermMethod (mean solar terms or true solar terms), doubleNoZhongqiRule (how to settle a year in which two months lack a mid-term); year-end intercalation additionally records scanTargetMonth, marking after which month the intercalary month hangs.

  • Year-end intercalation (the “second ninth month” system)　The intercalary month is placed at the end of the year. So it was in the six ancient calendars of the pre-Qin period and in the Qin Zhuanxu Calendar, the latter writing it as “second ninth month”, that is, hung after the ninth month; this set therefore records scanTargetMonth = 9.
  • Intercalation by absence of a mid-term　A synodic month that contains no mid-term is made the intercalary month. In the era of mean solar terms (before the Qing) there was necessarily one such month in a year and only one, and the criterion by which a “double absence” is settled does not apply, so this set records doubleNoZhongqiRule = NotApplicable.
  • The double-absence resolution under true solar terms　Since true solar terms came into use the interval between two winter mid-terms can be shorter than one synodic month, so that two months without a mid-term may occur within a single year, and the winter-solstice month itself may contain two mid-terms (the synodic month beginning 22 November 2033 contains both Minor Snow and the winter solstice). This site takes as its criterion “the first month without a mid-term after the synodic month containing the winter solstice is the intercalary month”, the second not being intercalated. The scan runs from one month after the winter-solstice month up to, and not including, one month before the next winter-solstice month; the winter solstice is itself a mid-term, so the winter-solstice month necessarily contains one and is not among the candidates. Intercalation has one further precondition: from one winter-solstice month to the month before the next there must be a full thirteen synodic months (a leap year) for an intercalary month to be placed; a stretch of only twelve months takes no intercalary month even if a month without a mid-term falls inside it.

5 · Dataset

The full data behind the definitions above are in the Chinese Calendar Public Dataset, which carries the astronomical constants of the calendars of successive dynasties, the intercalation rules and the shifting of the year-beginning, under CC BY 4.0: 10.5281/zenodo.22788686.

6 · Concept pages

The four pages below expand the concepts of the sections above; each carries four parts — definition, basis, data and common misconceptions — and gives the same definitions once more in machine-readable form at its foot:

The machine-readable definitions themselves — the JSON-LD block that closes the Chinese page — are published once, on kuangchujia.com/ns/, so that one DefinedTermSet node answers for the whole namespace.

本页由邝楚嘉搜集整理。Compiled and maintained by Chujia Kuang.