Saju, Tuổi & Nine Star Ki

One calendar, three cultures

Korean Saju, the Vietnamese zodiac of Tuổi and Japanese Nine Star Ki all run on the same Chinese machinery: ten Heavenly Stems, twelve Earthly Branches, the sixty-year cycle their pairings make, yin and yang, and the Five Phases of Wood, Fire, Earth, Metal and Water. The arithmetic is identical in all three countries, and each put it to a different use. Korea mapped the chart onto a Confucian household. Vietnam changed two of the animals and put the system to work deciding when a house could be built. Japan cut the eight characters down to two numbers and pointed them at the compass. This page follows each variant, after a short look at the Chinese groundwork all three inherited.

The Chinese groundwork

The stems and branches are older than astrology. Shang dynasty diviners were already labelling days with them on oracle bones some 3,300 years ago. The Zhou dynasty's Yijing added the idea that everything is in constant change, and in the Warring States period the philosopher Zou Yan is credited with setting out the Five Phases and the two cycles that link them: generation, in which Wood feeds Fire and Fire makes Earth, and control, in which Water puts out Fire and Metal cuts Wood.

Reading a person's fate from the calendar came later. The Tang official Li Xuzhong (c. 761–813) used three pillars, the year, month and day of birth, and read them mostly through the year and a set of spirit-stars. The decisive change is credited to Xu Ziping in the Song period. His method added the hour as a fourth pillar, giving four pillars of two characters each, and made the stem of the birth day, the Day Master, the centre of the whole reading. Xu Dasheng set the method down in the Yuanhai Ziping in the thirteenth century, and Wan Minying's Sanming Tonghui of 1578 gathered it into an encyclopedia.

Saju: Korea's four pillars

Saju (사주, 四柱) means four pillars. The Ziping method gained official standing in Korea under the Joseon dynasty, when fate calculation became one of the specialist fields examined for posts at the royal Bureau of Astronomy, with the Ziping texts among the set books. By the second half of the fifteenth century, reading a birth chart was a state qualification.

A Saju chart is drawn from the year, month, day and hour of birth. The month is counted by the 24 solar terms (jeolgi), so a chart changes at a solar boundary and not at a new moon. Each pillar holds a Heavenly Stem above, the active and visible side, and an Earthly Branch below, the hidden side and the circumstances. The eight characters together are the Saju Palja (사주팔자), and in everyday Korean palja has come to mean one's lot in life.

The ten stems carry the character sketches a beginner meets first. Gap (甲) is Yang Wood, a tall tree: straight, growing and inclined to lead. Eul (乙) is Yin Wood, a vine or grass that bends and survives. Byeong (丙), Yang Fire, is the sun and wants to be seen; Jeong (丁), Yin Fire, is a candle or a forge, warm and focused. Mu (戊) is a mountain, reliable and sometimes immovable, and Gi (己) is garden soil, practical and accommodating. Gyeong (庚) is raw ore or an axe, decisive and hard; Sin (辛) is a polished jewel or a blade, precise and exacting. Im (壬) is the ocean, broad and hard to contain, and Gye (癸) is rain or mist, quiet, sensitive and everywhere.

Reading strength and structure

The first question in any reading is whether the Day Master is strong (singang) or weak (sinyak): whether the other seven characters support it or drain it. Two schools answer the next question differently. The Eokbu school balances strength, prescribing the elements that would bring an overloaded or starved Day Master back to the middle. The Gyeokguk school looks for the chart's structure, the pattern set mainly by the month pillar, and reads the life through that pattern.

Both describe the other characters through the Ten Gods (Sipseong), named for their relation to the Day Master. Bigeop are the same element: Bigyeon is a peer of the same polarity, Geopjae a rival of the opposite polarity who pushes you to grow. Siksang is the element the Day Master produces, meaning expression, talent and, for women in the classical texts, children. Jaeseong is the element it controls, meaning money: Jeongjae is steady salaried income, Pyeonjae speculative or entrepreneurial capital. Gwanseong is the element that controls the Day Master, meaning bosses, institutions and discipline. Inseong is the element that feeds it, meaning mothers, teachers, study and protection.

The palace system

What sets Korean practice apart is how firmly it reads the four pillars as a family. The chart runs from the inherited and public to the private and self-made.

• Year pillar, the Ancestors' Palace. Grandparents, family inheritance and the circumstances a person is born into. In the common scheme it covers roughly ages 0 to 15.
• Month pillar, the Parents' Palace. Upbringing and, for most readers, the career: the working environment and the attitude to authority. Ages 16 to 30. Trouble here tends to show up as professional instability.
• Day pillar, the Spouse Palace. The stem is the Day Master (ilgan), the self. The branch beneath it is the spouse, so the partner sits in the most intimate position of the chart. Ages 31 to 45.
• Hour pillar, the Children's Palace. Children, subordinates, legacy, and the ambitions a person does not say out loud. Age 46 onward.

When the birth hour is unknown, a three-pillar reading still covers character and career, but it goes blind to later life and to the hidden drives the hour pillar holds.

Clashes, compatibility and the luck cycles

Branches that stand opposite each other on the circle of twelve clash (chung, 충). Ja-O, Rat against Horse, sets pure Water against pure Fire and is read as a sign of sudden reversals. Its meaning depends on the palace it strikes: in the day pillar a volatile marriage, in the month pillar an upheaval at work.

Historically Saju was consulted at turning points. Gunghap, marital compatibility, compared the charts of a prospective couple, looking for elements that generate each other and avoiding pairs in which one destroys the other. Each New Year brought a sinnyeon unse reading, set against the person's ten-year luck cycle (daeun), and people used both to time a new job or a property purchase.

Saju in Korea today

Since the 2010s Saju has had a large revival among Korean millennials and Generation Z. Readings are sold in fortune cafés, from street kiosks and through AI apps that draw a chart in seconds. Commentators link the boom to a hard job market and the pressure to lead a god-saeng, a perfectly productive life. Where seeing a therapist still carries stigma, a chart reading offers a private, low-stakes explanation. A bad stretch becomes a temporary imbalance of elements inside a ten-year cycle, which gives people a sense that the difficulty has a shape and an end. That comfort is real, and it works best alongside professional help for anyone who needs it, never in place of it.

Tuổi: the Vietnamese zodiac

In Vietnamese, tuổi means both a person's age and their birth year animal, and the Vietnamese zodiac keeps the full Chinese scaffolding of stems and branches. It changes the symbols. The twelve animals run Rat (Tý), Water Buffalo (Sửu), Tiger (Dần), Cat (Mão), Dragon (Thìn), Snake (Tỵ), Horse (Ngọ), Goat (Mùi), Monkey (Thân), Rooster (Dậu), Dog (Tuất) and Pig (Hợi).

The Cat is the famous difference. The fourth branch, 卯, is mǎo in Mandarin and Mão, or Mẹo in older usage, in Sino-Vietnamese, which sounds almost the same as mèo, cat. The strongest explanation is that the oral tradition followed the sound. Ecology helped the change stick: in wet-rice country rats threaten the grain store, and a cat is worth far more than a rabbit. Folklore adjusted the story of the Jade Emperor's Great Race to match. In the Chinese version the Rat pushes the Cat into the river and the Cat never finishes. In the Vietnamese one the Cat swims to the far bank in time to take fourth place.

The second change is quieter. The animal of the second branch, 丑, is 牛 in Chinese, a broad word for cattle. Vietnam fixes it as the water buffalo, trâu, the draught animal of the paddies. It should not be confused with a Chinese Water Ox year, which is one combination of stem and branch in the sixty-year cycle; the buffalo stands in every Sửu year.

For compatibility, Vietnamese practice relies on groups of animals. The tam hợp are four triangles of animals four years apart that support each other, such as Monkey, Rat and Dragon. The tứ hành xung are three squares of animals that clash, such as Rat, Horse, Cat and Rooster. Couples and business partners check both, and at Tết many families choose the first person to cross their threshold in the new year by the same rules.

Building a house by the calendar

The most exacting use of Tuổi today is in building. Breaking ground is thought to disturb the earth, so before construction the owner's lunar age is checked against three cycles.

Tam Tai, the three calamities, is a run of three consecutive years that returns every twelve years for each tam hợp group. Monkey, Rat and Dragon people, for example, meet it in the Tiger, Cat and Dragon years. Building then is said to invite obstacles and money trouble.

Kim Lâu, the golden tower, is found by dividing the lunar age by nine. A remainder of 1, 3, 6 or 8 is Kim Lâu, each tied to harm falling on a different part of the family: the owner, the spouse, the children or the livestock and property.

Hoang Ốc, the desolate house, counts the age through six stages: Nhất Cát (luck), Nhì Nghi (prosperity), Tam Địa Sát (earth killing), Tứ Tấn Tài (gain), Ngũ Thọ Tử (death) and Lục Hoang Ốc (desolation). The first, second and fourth are good; the other three are said to leave a house cold, abandoned or unlucky.

When an owner falls into these years and cannot wait, tradition allows mượn tuổi, borrowing an age. A man whose age is favourable, usually a relative, stands in as owner for the ground-breaking rites and the first days of work while the real owner stays away. When the house is finished it returns to the family who will live in it.

Nine Star Ki: Japan's compass

Nine Star Ki (九星気学, Kyusei Kigaku) is one of the most popular astrological systems in Japan, and in its present form it is young. Shinjiro Sonoda (1876–1961) formalised it in 1924, combining Flying Star feng shui, the Eight Mansions compass school and the Lo Shu magic square laid on the Later Heaven bagua. Where Saju works with eight characters, Kigaku works with two numbers.

The Honmei star (本命星) comes from the year of birth and is said to govern most of the adult personality and the course of life; practitioners often say 60 to 70 percent. For a birth year in the 1900s, add the last two digits, reduce the sum to one digit and subtract it from ten: for 1985, 8 + 5 = 13 and 1 + 3 = 4, and four from ten leaves 6. For the 2000s subtract from nine instead. A result of 0 counts as 9, and a result of 10 counts as 1. The year changes at Risshun, around 4 February, so anyone born in January or early February belongs to the previous year. The Getsumei star (月命星), from the birth month, accounts for the rest: childhood behaviour, appearance and the first impression a person makes.

The nine stars and the directions they own in the fixed chart:

• 1 White Water, north. Deep, private, independent, adaptable; keeps feelings inside.
• 2 Black Earth, southwest. Nurturing, loyal, conservative; builds a life slowly.
• 3 Jade Wood, east. Energetic, youthful, blunt; starts trends and tires of them.
• 4 Green Wood, southeast. Practical, flexible, sensitive; a natural counsellor who dislikes sudden change.
• 5 Yellow Earth, the centre. Forceful, practical, a born leader; the core of any group.
• 6 White Metal, northwest. Efficient, strong-willed, punctual, authoritative; sharp-tongued.
• 7 Red Metal, west. Charming, sociable, persuasive; enjoys comfort and luxury.
• 8 White Earth, northeast. Intelligent, well-groomed, demanding; luck that swings sharply.
• 9 Purple Fire, south. Charismatic, proud, impulsive; wants the spotlight.

Moving in the right direction

Most of the practice concerns geography. Each year, month and day has its own chart, a three-by-three grid based on the Lo Shu square, showing which star occupies which direction. The stars fly through the grid in a fixed order, so the whole map shifts every year. People consult it before moving house, travelling far or relocating a business, looking for their kippō, the lucky direction, and steering clear of the dangerous ones.

• Go-o-satsu, the Five Yellow killing: the direction the 5 Yellow Earth star occupies. Moving towards it is thought to bring ruin from within, such as self-sabotage and a failing household.
• Anken-satsu, the Dark Sword killing: directly opposite the 5. It is associated with accidents, betrayal and other harm from outside.
• Honmei-satsu: the direction your own Honmei star occupies. Moving towards yourself is said to exhaust your energy.
• Saiha and Getsuha: the direction opposite the animal of the year or of the month, associated with broken contracts and promises.

In 2026, a 1 White Water year, the 5 sits in the south, so south is Go-o-satsu and north is Anken-satsu. In 2027, a 9 Purple Fire year, the 5 moves to the north and the two directions swap. Practitioners take the measurement seriously: directions are read from the exact centre of the home, and they warn that steel reinforcement and iron balconies can throw off a compass reading.