The sexagenary cycle
— which ganzhi is your year, and why 60 rather than 120

What the sexagenary cycle is — two wheels turning together

The sexagenary cycle pairs ten heavenly stems with twelve earthly branches to make sixty names. In Chinese it is ganzhi (干支); in Korean, yuksipgapja.

The word that matters is together. The two wheels do not turn independently — they advance one notch each, at the same time.

Which is why it is 60, not 120

Ten stems times twelve branches is 120, and that is where most people stop. Only 60 pairs ever occur.

The reason is that the least common multiple of 10 and 12 is 60. A ten-notch wheel and a twelve-notch wheel turning in step return to their starting position after sixty steps. The other sixty combinations — pairs like jiachou — never appear at all.

The table shows it directly: an odd-numbered stem only ever meets an odd-numbered branch. Jia (1st) pairs only with zi, yin, chen, wu, shen and xu; yi (2nd) only with chou, mao, si, wei, you and hai.

The full table — jiazi to guihai

Years are listed only where that ganzhi actually fell between 1924 and 2043. The cycle repeats every sixty years, so add or subtract 60 to reach any other. Every element and polarity reading here is computed by our engine, not typed in by hand.

The ten heavenly stems

Is zi (子) yang or yin? There are two answers

Look up the polarity of the branches and books disagree. Neither is wrong — they are reading from two different places.

The two readings disagree on 4 branches — 子 (Ja) · 巳 (Sa) · 午 (O) · 亥 (Hae).

That is why 20 rows of the table above look like a yang stem sitting on a yin branch. Four branches come round five times each (4 × 5 = 20). Nothing is out of order — you are reading two scales at once.

Why the sixtieth birthday matters

Hwangap (還甲) means returning to jia. The ganzhi of your birth year comes back round after sixty years, and the birthday is named for that return.

Someone born in 1964, a jiachen year, reached their hwangap in 2024 — also jiachen. Hoegap (回甲) and hwagap (華甲) are other names for the same thing.

Hwangap falls at 60 by international reckoning, which is 61 in traditional Korean age. The old custom of holding the feast at 61 comes from counting the Korean way.

Not only years — months, days and hours too

The cycle is not reserved for years. Months, days and double-hours carry a ganzhi in exactly the same way. Write those four one under another and you have the eight characters of a birth chart.

• Year pillar — the ganzhi of the birth year. The zodiac animal comes from here
• Month pillar — the ganzhi of the birth month, divided by solar terms, not by the calendar month
• Day pillar — the ganzhi of the birth day. This is the pillar that stands for the person
• Hour pillar — the ganzhi of the birth hour. It changes every two hours

Each pillar carries one stem and one branch, so 4 × 2 = eight characters — which is what saju palja / bazi (四柱八字) means.

Common questions

Which years are jiazi years?

The recent ones are 1924 · 1984, and the next is 2044. They come round every sixty years.

Does the animal change at lunar new year or at lichun?

Both conventions are in use — one counts from lunar new year, the other from lichun (around 4 February). Chart reading uses lichun. If you were born between January and early February your year pillar depends on which convention is applied — you can check it on the traditional calendar.

If there are sixty ganzhi, are there only sixty possible charts?

No. Each of the four pillars has sixty possibilities, so 60⁴ = 12.96 million. Luck pillars and sex split it much further again.

Why is nayin (納音五行) not in the table?

Ganzhi are sometimes grouped in twos and given names like "gold in the sea" or "fire in the furnace". Our engine does not use that material when it reads a chart, so we have not printed it. Filling a column with something we do not use would make it look as though we do.