Interpretive systems

Gua Qi and calendrics

Take sixty hexagrams, spread them evenly across the solar year, and reserve four to preside over the solstices and equinoxes. Every date now has a figure and every figure has a season. It is the oldest systematic correlation in the tradition, and Daoist alchemy, Chinese medicine and professional divination all still run on parts of it.

60
hexagrams in the year
12
sovereign figures
24
solar terms

The components

Several overlapping correlations were built during the Han, and later traditions took different pieces of the apparatus for their own purposes.

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Sixty hexagrams across the year

Han China 1st century BCE

Meng Xi's founding correlation: sixty figures distributed evenly over the solar year, each governing about six and a fraction days. A date implies a hexagram and a hexagram implies a stretch of the calendar.

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The four regulators

Han China 1st century BCE

Kan, Li, Zhen and Dui are withheld from the sixty and set to preside over winter solstice, summer solstice and the two equinoxes, in their capacity as water, fire, thunder and lake.

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The twelve sovereign hexagrams

Han China Han

Twelve figures in which yang lines enter at the bottom and rise until the whole is yang, then yin does the same. They map the twelve months and are the most widely reused part of the whole scheme.

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The twenty-four solar terms

China Han onward

The agricultural year divided into twenty-four periods, from Beginning of Spring to Greater Cold. The hexagram calendar is fitted onto them, which ties the figures to weather and farming rather than to abstraction.

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The seventy-two pentads

China Han onward

Each solar term subdivides into three five-day periods with their own phenological markers: insects stirring, peach trees blossoming, hawks changing. The finest grain of the calendar the hexagrams are laid over.

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Na Jia

Han China 1st century BCE

Jing Fang's attachment of the Heavenly Stems and Earthly Branches to hexagram lines, binding the figures to the sexagenary cycle. The bridge from calendrics into divination proper.

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Yao Chen

Han China 2nd century CE

Zheng Xuan's rival distribution of the twelve branches across the lines, giving a different set of temporal correspondences. It competed with Na Jia for centuries.

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Reading wind and weather

Han China Han

Han specialists used the scheme to judge whether the season's qi had arrived on time, treating unseasonable weather as a portent about the state. This was the calendar's original working purpose.

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The alchemical firing times

China 2nd century CE onward

Inner alchemy reads the twelve sovereign hexagrams as a schedule for raising and lowering internal heat, mapping the annual cycle onto a day or a single session. The scheme's most consequential afterlife.

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Seasonal strength in divination

China Han onward

In Six Lines practice a line's phase is strong or weak according to the month and day of the cast. The same hexagram can yield opposite verdicts in spring and autumn, and this is where that comes from.

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Medicine and seasonal qi

China and Korea Han onward

Chinese medicine's account of seasonal influence on the body shares this correlative framework, and Korean Sasang medicine later built a constitutional system on the four images.

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Geomantic timing

China later tradition

Date selection for building, burial and moving draws on the same stem-and-branch machinery, so the calendar remains commercially significant across the Chinese-speaking world.

Origins and afterlives

Where the scheme came from, what was built on it, and how much of it is still load-bearing today.

Meng Xi

fl. 1st century BCE Han China

Credited with the Gua Qi correlation itself. His teaching became one of the officially recognised Yi lineages at the Han academy, and every later calendrical scheme builds on his distribution.

Jing Fang

77–37 BCE Han China

Extended calendrics into divination with Na Jia and the eight palaces, and used hexagram-calendar reasoning to submit portents to the throne. It got him executed at forty-one.

Zheng Xuan

127–200 Han China

Applied Yao Chen to the Changes, a competing distribution of the branches. His Yi work survives only in quotation by later scholars.

The Yi wei apocrypha

1st century BCE to 1st century CE China

Prognosticatory texts that read the hexagram calendar as political prophecy. Hugely influential, repeatedly banned from the fifth century, and surviving mostly as fragments.

The Cantong Qi

2nd century CE China

The founding text of inner alchemy, which takes the twelve sovereign hexagrams as its timing device. The single most important document in the calendar scheme's afterlife.

Han calendar reform

104 BCE Chang'an

The Taichu reform placed calendrical science at the centre of Han statecraft. Hexagram calendrics belongs to that context: fixing the year and reading the cosmos were the same undertaking.

Shao Yong's great cycles

1011–1077 Luoyang

Extended calendrical thinking to a chronology of the universe measured in cycles of nearly a hundred and thirty thousand years, with hexagrams marking the eras.

The sovereign hexagram sequence

Han China

Return, Approach, Peace, Great Power, Breakthrough, The Creative, Coming to Meet, Retreat, Standstill, Contemplation, Splitting Apart, The Receptive. Eleventh month to tenth, light waxing and waning.

The Qing reconstruction

18th century Suzhou

Evidential scholars reassembled the Han calendrical systems from quotations, since the original commentaries had been lost. Most of what is known about Meng Xi's scheme comes through that work.

The farming almanac

continuous China

The solar terms remain in everyday use for agriculture and festivals across China, Korea, Japan and Vietnam, whether or not anyone attaches hexagrams to them.

The solar terms today

2016 China

The twenty-four solar terms were inscribed on UNESCO's intangible heritage list, a reminder that the calendar under this scheme is a living framework rather than an antiquarian one.

The wider Han context

Han China

Gua Qi is one component of the symbol-number school, which built a much larger apparatus around it. The Xiangshu school page covers the rest.

Fitting a book to a year

The founding move of Han hexagram calendrics is easy to state. Take sixty of the sixty-four figures and distribute them evenly across the solar year, so each governs a little over six days. Reserve the remaining four, Kan, Li, Zhen and Dui, to preside over the winter solstice, the summer solstice and the two equinoxes, in their capacities as water, fire, thunder and lake.

Every date in the year now has a hexagram, and every hexagram has a stretch of the calendar. The correlation is attributed to Meng Xi in the first century BCE, and it became the base layer of the whole symbol-number enterprise.

It matters that this happened under the Han. Calendar reform was a central act of state, the Taichu reform of 104 BCE had made astronomical accuracy a matter of dynastic legitimacy, and specialists who could correlate the classic with the year were useful at court. Getting the calendar right and reading the cosmos correctly were understood as one problem.

The twelve sovereign hexagrams

Inside the scheme sits a smaller sequence that has outlived everything around it. Twelve figures in which yang lines enter at the bottom and rise one at a time until the figure is entirely yang, after which yin lines do the same:

Return, Approach, Peace, Great Power, Breakthrough, The Creative, then Coming to Meet, Retreat, Standstill, Contemplation, Splitting Apart, The Receptive.

Read as months, they run from the eleventh, containing the winter solstice, round to the tenth. Return is the solstice itself, one yang line reappearing after the year's darkest point, which is why that hexagram carries the weight it does in the tradition. The Creative is high summer, all yang. The Receptive is the depth of winter.

Reading the weather

The scheme's original working purpose was diagnostic. If the season's qi arrived on time, the weather at each solar term would match what the governing hexagram implied. If it did not, something was wrong, and what was wrong was generally taken to be the conduct of government.

The Han apocrypha, the Yi wei, extended this into outright political prophecy, correlating the hexagram calendar with dynastic fortunes. They were influential enough to be banned repeatedly from the fifth century onwards, and survive mostly as quotations in works attacking them.

What still runs on it

Three things, and they are not marginal.

Inner alchemy took the twelve sovereign hexagrams as its timing device. The Cantong Qi maps the annual cycle onto a day, or onto a single session of practice, and uses the sequence to schedule the raising and lowering of internal heat. Every later alchemical text inherits this, which makes the firing times the calendar's most consequential afterlife.

Divination kept the seasonal machinery through Na Jia. In Six Lines practice, a line's Five Phase agent is strong or weak depending on the month and day of the cast, so the same hexagram yields different verdicts in different seasons. That rule descends directly from Han calendrics.

The solar terms themselves remain in daily use. The twenty-four terms and their seventy-two five-day subdivisions, with markers like insects stirring or hawks changing, still structure agriculture and festivals across China, Korea, Japan and Vietnam. They were added to UNESCO's intangible heritage list in 2016. Most people using them attach no hexagrams at all, which is a fair indication of which layer was load-bearing.

What to make of it

Two honest observations.

The correlation is arbitrary in the sense that nothing about a hexagram determines which week of the year it should govern. Sixty figures were fitted to a year because sixty divides into it conveniently, and the assignment follows an order rather than a meaning. Later schemes disagreed about details precisely because there was no fact to appeal to.

It is also genuinely productive. Laying a closed formal system over the year gave Chinese thought a way to talk about process, phase and timing that ran through medicine, alchemy, agriculture and statecraft for two millennia. The twelve sovereign hexagrams in particular are a compact and rather beautiful model of any cycle in which something accumulates, peaks and recedes.

Much of the apparatus built around this scheme was lost after the third century and had to be reconstructed by Qing scholars from quotations. The Xiangshu school page covers that story and the rest of the symbol-number toolkit.

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