The Sixty-Year Cycle: Stems, Branches, and Korean Year Names
Maker's note: 기준일 2026-10-09. Written by the AZET team (AZET 운영팀), who operate the services mentioned at the end. Seowoon's Korean site, seowoongwan.com, is operated by 에이치컴퍼니(사업자등록번호 316-47-00948, 통신판매업 신고 2023-부산강서구-1073); the menu name below is as shown there on October 9, 2026. Anything touching on saju is for fun and reference only and is not a prediction.
Korean history books are full of events named with two syllables that look like code: the Imjin War, the Gapsin Coup, the Eulsa Treaty, the Gabo Reforms. They are dates. Each name is a year in a sixty-year counting cycle that East Asia used for well over two thousand years, and which still sets the labels on calendars, the timing of a famous birthday, and all eight characters of a saju chart. Once you know how the cycle is built, a lot of Korean culture comes into focus.
Two wheels
The cycle is made from two separate lists.
The ten heavenly stems (천간): 갑, 을, 병, 정, 무, 기, 경, 신, 임, 계. Read as gap, eul, byeong, jeong, mu, gi, gyeong, sin, im, gye.
The twelve earthly branches (지지): 자, 축, 인, 묘, 진, 사, 오, 미, 신, 유, 술, 해. Read as ja, chuk, in, myo, jin, sa, o, mi, sin, yu, sul, hae. These are the ones tied to the twelve zodiac animals, from rat through pig.
Picture two gears turning together, one with ten teeth and one with twelve. Start with the first stem paired with the first branch: 갑자. Advance both by one: 을축. Then 병인, and so on. After ten steps the stems start over while the branches still have two to go, so the pairings shift.
Why sixty and not 120
Ten times twelve is 120, yet the cycle has only sixty pairs. The reason is that both wheels advance together, so a stem in an odd position only ever meets branches in odd positions, and even meets even. Half of the conceivable pairings never occur. The wheels return to their starting alignment after sixty steps, the least common multiple of ten and twelve.
| Position | Pair | Reading | Recent year |
|---|---|---|---|
| 1 | 갑자 | gapja | 1984 |
| 41 | 갑진 | gapjin | 2024 |
| 42 | 을사 | eulsa | 2025 |
| 43 | 병오 | byeongo | 2026 |
| 60 | 계해 | gyehae | 2043 |
The whole set is called yuksip gapja (육십갑자), "the sixty gapja," after its first member.
Elements and colours
Each stem carries one of the five elements and a yin or yang polarity: the first two are wood, the next two fire, then earth, metal, and water. Tradition also assigns each element a colour: blue-green for wood, red for fire, yellow for earth, white for metal, black for water.
That is where popular labels such as "year of the blue dragon" come from. The stem gives the colour, the branch gives the animal. The year 2024 was 갑진, wood plus dragon, hence blue dragon. The year 2026 is 병오, fire plus horse, hence red horse. These labels are fun and widely used in the media each January, but they are simply a readable form of the year's two characters.
Where you meet the cycle in Korean life
History. The Imjin War is named for the imjin year, 1592, when it began. The Gapsin Coup took place in 1884, a gapsin year. Because the names repeat every sixty years, context tells you which occurrence is meant.
Hwangap. The sixtieth birthday, hwangap (환갑), literally means the return of the gap, the cycle coming back to the pairing of one's birth year. It was traditionally a major celebration, since reaching it was once a real feat of longevity. Families today often mark it more quietly and hold the larger party at seventy instead.
The zodiac question. Asking someone's animal sign, their tti (띠), is a soft way of working out their age. The animal is the branch half of the year pair.
Almanacs. Traditional calendars label not only years but months, days, and two-hour periods with pairs from the same sixty.
How it becomes a saju chart
That last point is the bridge to saju. A birth moment has four time units: year, month, day, hour. Each is expressed as one pair from the sixty. Four pairs make eight characters, which is the literal meaning of the phrase 사주팔자, four pillars and eight characters.
The day count is worth a moment's wonder. Days have been numbered through the sixty-pair cycle continuously, one after another, for a very long time, independent of months and years. Finding the day pillar for a birth date means locating that date in an unbroken sequence, which is why saju calculators rely on calendar tables instead of a simple formula.
The year pillar has a quirk of its own. In saju practice the year usually turns at ipchun, the "start of spring" solar term around February 4, not on January 1. Someone born in mid-January 2026 would generally be given the 을사 year pillar and not 병오.
What the cycle is, and is not
The sixty-pair system is a calendar, an elegant way of counting. The fact that a year is labelled fire-horse describes a position in a sequence. Any qualities attached to that label, for the year or for people born in it, are tradition and storytelling. Some of that storytelling has been unkind in the past, particularly toward women born in certain years, and it deserves to be left there.
Enjoy the cycle as a piece of intellectual heritage: a base-sixty clock for human lifetimes that people have been reading for millennia.
Seeing your own four pairs
Seowoon (서운관), the Korean saju service in the AZET family, displays the four pillars of a birth date as part of its readings at seowoongwan.com. The general reading 도사님 정통사주 is the place to see your year, month, day, and hour pairs laid out. The site is Korean-language, so use browser translation for the surrounding text.
FAQ
What is the sixty-year cycle? A sequence of sixty pairs formed by combining ten heavenly stems with twelve earthly branches, used across East Asia to name years, months, days, and hours.
Why are there only sixty combinations? The two lists advance together, so only same-parity positions meet. The pattern repeats after sixty steps.
What is hwangap? The sixtieth birthday in Korea, marking the return of the cycle to one's birth-year pair.
Why is 2026 called the year of the red horse? Its pair is 병오. The stem 병 is fire, associated with red, and the branch 오 is the horse.
How does this relate to saju? A saju chart writes the birth year, month, day, and hour as four pairs from the cycle. Readings of it are for fun and reference.
Learn more
Seowoon is listed among the AZET services at https://azet.io, next to the free early-access waitlist for azet, the AI assistant we are building. The next time a Korean drama mentions a year by a two-syllable name, you will know there are two small gears turning behind it.