Heavenly Stems

Meaning

The ten Heavenly Stems, tiāngān, are Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren and Gui: 甲乙丙丁戊己庚辛壬癸. They are the oldest counters of Chinese time, ten signs that named the ten days of the week of the Shang kings more than three thousand years ago, and they still stand at the top of every pillar of the calendar, over the branch of each year, month, day and double hour.

Each stem is one of the five phases in its yang or its yin form, taken in the order of the generating cycle, the yang stem of each pair first: Jia and Yi are Wood, Bing and Ding Fire, Wu and Ji Earth, Geng and Xin Metal, Ren and Gui Water. The yang stem is the phase going out, open and whole; the yin stem is the same phase turned inwards, finer and more pliant. The tradition pictures the ten as the tall tree and the vine, the sun and the lamp, the mountain and the field, the axe and the jewel, the sea and the rain.

Read in order, the ten also tell one story, the year of a growing plant: the husk splits, the shoot pushes through, it opens in the light and grows strong, flourishes and takes its form, ripens and changes, is made new, is carried within as seed and waits, measured, for the next spring. That is how the Han historians explained the names, and BaZi still reads the stems as moments of one movement rather than ten things apart. None of the ten is better than another: each is a way of being one phase, with the gifts and the limits of its image.

In practice

• In BaZi, the stem of the day pillar is the Day Master, the self; every other stem, shown at the top of a pillar or hidden in a branch, is one of the Ten Gods by how its phase meets the Day Master’s and whether their polarities agree. Four pillars show four stems and hide up to eight more.
• Stems that meet: stems five apart combine, Jia with Ji, Yi with Geng, Bing with Xin, Ding with Ren, Wu with Gui, each pair leaning towards a phase of its own (stem combinations); stems six apart clash, Jia with Geng, Yi with Xin, Bing with Ren, Ding with Gui, while the two Earth stems, at the centre, clash with none (stem clashes).
• In time: counted from Lichun, the year’s stem follows the last digit of the year: 4 Jia, 5 Yi, 6 Bing, 7 Ding, 8 Wu, 9 Ji, 0 Geng, 1 Xin, 2 Ren, 3 Gui. The months take their stems from the year’s by the rule of the “five tigers”, the double hours theirs from the day’s by the rule of the “five rats”.
• In Chinese astrology, the stem gives each year’s animal its phase: 2026, a Bing year of the Horse, is the year of the Fire Horse, and Ulune’s portraits of the sixty animal-and-phase pairs read the stem that way.
• In Feng Shui, eight stems are eight of the 24 mountains of the luopan, two in each cardinal direction; Wu and Ji, the Earth stems, belong to the centre and have none.

Across traditions

• Everyday Chinese still uses the stems as the first letters of a list, as English uses A, B, C and D: 甲方 and 乙方 are Party A and Party B of a contract, and chemistry names the first ten alkanes after them, from 甲烷 jiǎwán, methane, to 癸烷 guǐwán, decane.
• Japan, Korea and Vietnam count with the same ten. Japanese reads them as the elder and the younger brother of each phase, kinoe, “elder brother of wood”, for Jia and kinoto for Yi, down to mizunoe and mizunoto; Korean says gap, eul, byeong; Vietnamese Giáp, Ất, Bính.
• The sixtieth birthday is the stems’ and branches’ return: after sixty years the pillar of one’s birth year comes round again, which Japan celebrates as kanreki and Korea as hwangap.
• Western astrology has no counter of the kind; the nearest is the seven-day week named after the seven classical planets, as the Shang week of ten days was named after the stems.

Origin and history

The stems are older than the phases they are read with. On the oracle bones of the late Shang dynasty, around 1250–1046 BC, they name the ten days of the xún 旬, the week of ten days, and the kings were honoured on the day of their name: Wu Ding, under whom most of the bones were written, and Di Xin, the last of the dynasty, carry stems in theirs. Joined in turn to the twelve Earthly Branches they made the sixty-day count, written out in full on one of the bones, and that count of days has run without a break since at least the 8th century BC.

The stems were joined to the phases, the seasons and the directions in the Warring States period: the monthly ordinances of the Lüshi Chunqiu (c. 239 BC) give spring the days Jia and Yi, summer Bing and Ding, the centre Wu and Ji, autumn Geng and Xin, winter Ren and Gui. The Han historians Sima Qian (c. 94 BC) and Ban Gu (1st century) explained each name by a word of like sound, a stage of growing things, and Xu Shen’s dictionary (c. 100) did the same from the shapes of the characters. Under the Song dynasty the Zi Ping school put the day’s stem at the centre of a birth, and the Di Tian Sui gave each of the ten the verse that BaZi still reads.

How Ulune calculates it

Ulune numbers the stems from Jia and reads each from its pillar’s place in the sixty-cycle, the place counted in tens. The year’s pillar turns at the exact moment of Lichun, the Sun at 315°, and the month’s at each solar term that opens a month; the month’s stem follows from the year’s by the five tigers (a Jia or Ji year opens with a Bing-Yin month), which Ulune counts as an unbroken run of months through the cycle, twelve a year, from Bing-Yin in the Tiger month of 1984. The day’s pillar comes from the count of days, the Julian day number plus 49, modulo 60, which makes 1 January 2000 a Wu-Wu day; the hour’s stem follows from the day’s by the five rats. Day and hour are read on true solar time at the birthplace by default, the day turning at 23:00; Settings offer local mean time or the clock on the wall, and midnight or the split Rat hour.

Each stem’s phase and polarity are fixed, Jia and every second stem after it yang. The Ten God of a stem comes from its phase’s step from the Day Master’s round the generating cycle and from whether their polarities agree; the stems each branch holds are the common table of hidden stems, with their weights.

Correspondences