Chinese astrology: zodiac animals, Gan-Zhi & Four Pillars

The short answer

Chinese astrology is a broad label for diverse interpretive traditions using calendrical and cosmological frameworks. The familiar twelve year animals are one entry point; they are not a complete account of these traditions.

A historical object, not an origin myth

The Metropolitan Museum of Art holds an eighth-century Tang-dynasty set of twelve zodiac animals, accession 2000.662.7a–l. These earthenware figures belonged to a funerary setting. They are a tangible witness to calendrical imagery in material culture.

The object’s date tells us when this particular set was made. It does not supply a single invention date for Chinese astrology or prove that every later interpretive practice was already present. A catalog record can support an account of an object without answering every question about the tradition around it.

Why ten and twelve produce sixty

The Hong Kong Observatory describes Gan-Zhi as paired sequences of ten heavenly stems and twelve earthly branches. Both sequences advance one step at a time. Their starting pair returns after sixty steps.

The original figure uses numbered positions to make the counting visible. It is a cycle demonstration, not a conversion of a Gregorian date.

Try the count yourself

At position 1, pair stem 1 with branch 1. At position 11, the stem has returned to 1 while the branch has reached 11. At position 13, the branch returns to 1 while the stem is 3. Position 61 repeats the starting pair.

The two counts realign after the least common multiple of 10 and 12: 60. They do not generate every possible pairing in a 10 × 12 table. Advancing together preserves matching odd or even positions, so the cycle visits 60 of the 120 possible combinations. You can test the pattern with two numbered paper strips and a pointer.

Four Pillars: more than a year animal

In the Four Pillars or BaZi framework, the year, month, day and hour each contribute a stem–branch pair: eight characters in total. The Observatory documents this calendar structure. A birth-year animal provides only part of the information used in this approach.

Which year boundary is being used?

The Hong Kong Observatory marks the Gan-Zhi calendar year change at Lunar New Year. Its explanation also notes that some divinatory practice uses Li Chun, the solar term called Spring Commences. The choice matters near the boundary.

The Observatory gives a concrete example for 2018: Spring Commences fell on 4 February, while Lunar New Year fell on 16 February. A date between those days therefore belongs to the interval where these two year-change conventions differ. This illustrates why asking only for a Gregorian birth year can be insufficient. It does not calculate the other three pillars.

When reading a report, ask which year boundary, month convention, time handling and source it uses. Avoid assuming that the rules of a public calendar automatically supply every rule of a divinatory method.

Compare the questions, not just the animals

A Western Sun sign locates the Sun within a chosen zodiac; a Chinese year-animal label belongs to a calendrical sequence. Neither label is a translation of the other. Two people sharing a year animal need not share a Sun sign, and a year animal alone does not supply a Four Pillars reading.

Our comparison guide keeps those frameworks separate. For a useful note-taking exercise, write “what is being counted?” above one column and “what interpretation is being offered?” above another. The first column can contain the cycle demonstration; claims about personal character belong in the second and need to be considered as interpretations.

A question to take with you

What information does a year-animal label leave out, and which convention would you need before reading further?