Ding

Ding is the fourth of the ten Heavenly Stems (tiangan). Its element is Fire and its polarity is yin, so Ding is glossed as yin Fire, likened in tradition to a candle flame or lamplight, smaller and more contained than the blazing yang Fire of Bing but steady and illuminating. As one of the ten stems it pairs with the twelve Earthly Branches to build the sexagenary cycle of sixty used to number years, months, days, and double-hours. Each of the five phases appears among the stems once as yang and once as yin, and Ding carries the yin aspect of Fire. These are the conventions of the Chinese calendrical and cosmological tradition, drawn on in the almanac and in the four-pillars art of fate calculation.

Ding is the fourth Heavenly Stem, paired with Bing under the Fire phase but carrying the Yin polarity, likened traditionally to a candle, lamp or hearth fire rather than Bing's sun, a contained and tended flame instead of a blazing one. As an even-numbered stem it combines only with the six Yin Earthly Branches, Ox, Rabbit, Snake, Goat, Rooster and Pig, within the sixty-term sexagenary cycle used to name years, months, days and hours. In four pillars (BaZi) astrology a Ding day master is read as warm but more focused and inward than a Bing day master, giving steady illumination rather than heat that spreads unchecked, and the tradition associates the stem with refinement, culture and careful attention. Ding also has a long administrative use as an ordinal marker, the fourth item in a list, paralleling the way Jia through Gui once numbered examination results and official rankings before Arabic numerals became standard.

Every stem has a partner among the other nine, and the five pairings, called the combinations of the heavenly stems, are fixed: each stem combines with the one five places away from it. Ding pairs with Ren, and the tradition holds that a combined pair takes on a phase of its own distinct from either stem's native phase. The pairing is used in almanac work and in fate calculation, where a combination in a chart is read as a binding between the two positions that carry it.

The ten stems are older than the sexagenary cycle they now form half of. On the Shang oracle bones of the second millennium BCE they name the ten days of the xun, the Shang week, and Shang kings are known to history by posthumous names built on them, so a stem was a unit of the working calendar before it was a term of cosmological art. The five-phase and yin-yang readings attached to the stems are later, systematised under the Han, and the atlas records the two layers as two layers.

Ding is yin Fire, the lamp against the sun of Bing, and the contrast is the standard illustration of what yin and yang mean within a single phase: not weaker and stronger but inward and outward, contained and radiating. Ding also names one of the best known Shang kings, Wu Ding, whose reign produced a large part of the surviving oracle bone corpus.

The stem's own attributes here are Fire and yin polarity. Those two facts fix its place in the run of ten, since the stems proceed through the five phases in generation order taking the yang member first and the yin member second, and they fix how it is read wherever it appears, in the year, the month, the day or the double hour of a Four Pillars chart.

Sources Chinese Mathematical Astrology: Reaching Out to the StarsHo Peng Yoke with The Chinese Sexagenary Cycle and the Ritual Origins of the CalendarAdam Smith