The Sixty Jiazi and Nayin

Pair the ten Heavenly Stems with the twelve Earthly Branches in order and the combinations repeat every sixty steps. This sixty-step cycle, named after its first pair Jia Zi (甲子), is the backbone of the Chinese calendar and of every BaZi chart.

Why sixty?

Stems advance one step at a time through a cycle of ten, and branches through a cycle of twelve. Starting both at the beginning — Jia with Zi — they return to Jia Zi together only after sixty steps, the smallest number that both ten and twelve divide into. Because both cycles move together, a yang stem always meets a yang branch and a yin stem a yin branch. That is why there are sixty pairs, not 120.

The same cycle is used on four time scales, and each gives one pillar of your chart:

• Years: one pair per year. 1984 and 2044 are both Jia Zi years.
• Months: one pair per solar month, so the cycle repeats every five years.
• Days: one pair per day, unbroken for more than two thousand years. Your day pillar comes from this count.
• Hours: one pair per two-hour period, so the cycle repeats every five days.

Nayin: the "sound" element of each pair

Classical astrology also gives each two neighbouring pairs a shared element called Nayin (納音, "received sound"), with a poetic name such as "Gold in the Sea" or "Fire in the Furnace". The Nayin element often differs from the elements of the stem and branch themselves: Jia Zi has a Wood stem and a Water branch, but its Nayin is Metal. Older fortune-telling used the Nayin of the birth year as a kind of "life element". Modern BaZi practice relies on the stems and branches directly, and Fate Hall's scores do not use Nayin; it is listed here for reference and for readers who meet it in other books.

The full cycle

The table lists every pair with two of its years between 1924 and 2043. Remember that a BaZi year starts at the Beginning of Spring (around 4 February): someone born on 20 January 1984 belongs to the previous pair, Gui Hai, not Jia Zi.

Reading a pillar

Each pillar in your chart is one of these sixty pairs. The stem shows the element that is visible on the surface, and the branch shows the season, the time of day and the hidden elements underneath. When a later year brings the same pair as one of your pillars, traditional texts say that pillar is "activated", and its themes come up again.

Common questions

How does Fate Hall know my day pillar? It counts days from a fixed reference date with the same continuous sixty-day cycle used in East Asian almanacs, after adjusting your birth time to local solar time. The full method and its checks are on the Sources & methods page.

Why is it called "Jiazi"? Jia is the first stem and Zi the first branch. The word also means "a sixty-year cycle", and turning sixty — completing one full cycle — is traditionally celebrated in Korea, China and Japan.

Related guides

• The Ten Heavenly StemsJia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren and Gui: the element, yin or yang and traditional image of each Heavenly Stem, and what it says as your Day Master.
• The Twelve Earthly BranchesThe twelve branches from Zi (Rat) to Hai (Pig): their element, solar month, double hour and hidden stems, and the harmonies and clashes between them.
• The Five ElementsHow Wood, Fire, Earth, Metal and Water feed and control one another, which stems and branches carry each element, and how to read the balance in your chart.