Heavenly Stems and Earthly Branches — A Complete Guide

An in-depth look at the 10 Heavenly Stems (Cheongan) and 12 Earthly Branches (Jiji), the building blocks of East Asian metaphysics. Learn the principles behind the 60 Sexagenary Cycle (Yukship Gapja), the structure of the Four Pillars (Saju), and how they connect to time, direction, and the seasons.

Overview of Heavenly Stems and Earthly Branches

The Heavenly Stems (Cheongan, 天干) and Earthly Branches (Jiji, 地支) are the most fundamental components of East Asian metaphysics. The Heavenly Stems consist of 10 characters representing the energy of heaven, while the Earthly Branches consist of 12 characters representing the energy of earth. Together they are called "Ganji" (干支, Stems and Branches), and since ancient times they have been used to mark years, months, days, and hours.

The 60 Sexagenary Cycle (Yukship Gapja, 六十甲子), created by combining the Stems and Branches, was the standard system for measuring time in East Asia. In Saju Myeongrihak (Four Pillars of Destiny), it remains the key tool for interpreting a person's fate. It is still widely used today in the lunar calendar and in Saju readings.

The 10 Heavenly Stems in Detail

The 10 Heavenly Stems are Gap (甲), Eul (乙), Byeong (丙), Jeong (丁), Mu (戊), Gi (己), Gyeong (庚), Sin (辛), Im (壬), and Gye (癸). Each is associated with one of the Five Elements and classified as either Yang (positive) or Yin (negative).

Gap and Eul — The Wood Stems

Gap Wood (甲木) is like a towering tree. It grows straight upward, and people with Gap as their Day Stem tend to be proud, possess natural leadership, and carry a strong sense of responsibility. Just as a great tree does not bend easily in the wind, they show unwavering determination in difficult situations. However, they can sometimes be stubborn and lack flexibility.

Eul Wood (乙木) is like grass or flowering plants. Flexible and highly adaptable, it possesses the vitality to thrive even in the smallest crevices. People with Eul as their Day Stem are "gentle on the outside, strong on the inside." They appear soft and accommodating but harbor deep inner strength. They are sociable and cooperative, with a remarkable ability to adjust themselves to their surroundings.

Byeong and Jeong — The Fire Stems

Byeong Fire (丙火) is like the sun itself. It shines brightly and intensely upon the world, with a transparent personality that hides nothing. People with Byeong as their Day Stem are passionate, positive, and radiate energy that brightens those around them. However, they can become self-centered at times, and their emotional expression may occasionally be excessive.

Jeong Fire (丁火) is a gentle, warm flame — like a candle or starlight. People with Jeong as their Day Stem are meticulous and wise, possessing keen insight much like a light that illuminates a path through darkness. They tend to have a talent for academics or the arts, and they are the type to quietly but steadily fuel their inner passion.

Mu and Gi — The Earth Stems

Mu Earth (戊土) symbolizes a great mountain or vast land. People with Mu as their Day Stem are grounded and stable, with a broad capacity to embrace others — the kind of person many rely on. Their steady, unshakable character serves as an anchor for those around them. On the other hand, they may be slow to adapt to change and somewhat set in their ways, taking time to adjust to new environments.

Gi Earth (己土) is like the soil of a cultivated field or garden. With a nurturing, mother-like personality that fosters growth in all things, they are practical and deeply considerate. People with Gi as their Day Stem are humble and resourceful, always looking after those around them. They pursue tangible results and dislike waste.

Gyeong and Sin — The Metal Stems

Gyeong Metal (庚金) is like raw ore, iron, or a blade. People with Gyeong as their Day Stem are decisive and determined, with a righteous nature that cannot tolerate injustice. They are combative and fiercely competitive, with the drive to charge straight toward their goals. However, they can sometimes come across as rough or aggressive.

Sin Metal (辛金) symbolizes a polished gemstone or precious metals. People with Sin as their Day Stem are sharp and refined, with a strong appreciation for beauty. They pay attention to their appearance, have excellent taste, and tend toward perfectionism. With high self-esteem and a critical eye, they can quickly identify the shortcomings of others.

Im and Gye — The Water Stems

Im Water (壬水) is like the vast ocean or a great river. People with Im as their Day Stem are broad-minded, enterprising, and deeply wise. They overflow with ideas and creativity, and their bold nature gives them the ability to see the big picture. However, they may lack consistency and become scattered, sometimes neglecting finer details.

Gye Water (癸水) is like dew, rain, or a quiet spring — small and clear. People with Gye as their Day Stem possess strong intuition, rich emotions, and heightened spiritual sensitivity. Though quiet and introverted, they are remarkably observant and never miss the subtle changes happening around them. They often excel in academic, religious, or artistic fields.

The 12 Earthly Branches in Detail

The 12 Earthly Branches are Ja (子), Chuk (丑), In (寅), Myo (卯), Jin (辰), Sa (巳), O (午), Mi (未), Sin (申), Yu (酉), Sul (戌), and Hae (亥). Each Branch corresponds to an animal of the Chinese zodiac, as well as a compass direction and a time period.

The 60 Sexagenary Cycle (Yukship Gapja)

The 60 Sexagenary Cycle is formed by pairing the 10 Heavenly Stems with the 12 Earthly Branches in sequential order. It begins with Gapja (甲子) and ends with Gyehae (癸亥), producing a total of 60 unique combinations. Because the least common multiple (LCM) of 10 and 12 is 60, exactly 60 pairings complete one full cycle. This cycle is called "Hwangap" (還甲), and the Korean tradition of celebrating a person's 60th birthday originates from this concept — it marks the moment when the Sexagenary Cycle has turned full circle and returned to its starting point.

The pairing rule works as follows: Yang Stems combine only with Yang Branches, and Yin Stems combine only with Yin Branches. For example, Gap (Yang) pairs with Ja (Yang), In (Yang), Jin (Yang), and so on, while Eul (Yin) pairs with Chuk (Yin), Myo (Yin), Sa (Yin), and so forth. This is why there are 60 combinations rather than 120.

The Beginning of the Cycle: Starting from Gapja (甲子)

The cycle begins with the first combination, Gapja (甲子), and continues through Eulchuk (乙丑), Byeongin (丙寅), Jeongmyo (丁卯), and Mujin (戊辰). Each step advances both the Stem and the Branch by one position. After the 10th Stem (Gye), the sequence loops back to Gap; after the 12th Branch (Hae), it loops back to Ja. When the 60th combination, Gyehae (癸亥), is reached, one full cycle is complete.

The Four Pillars of Saju

Saju (四柱) literally means "Four Pillars." Each pillar represents a person's year, month, day, and hour of birth, expressed in Heavenly Stems and Earthly Branches.

• Year Pillar (Yeonju): Represents the year of birth. It symbolizes ancestral fortune, the social environment, and early childhood (ages 1–15).
• Month Pillar (Wolju): Represents the month of birth. It symbolizes parental fortune, the upbringing environment, and young adulthood (ages 16–30).
• Day Pillar (Ilju): Represents the day of birth. It symbolizes the self and one's spouse, as well as middle age (ages 31–45). The Day Stem (Ilgan) is especially important, as it represents "the self" — the single most significant character in a Saju chart.
• Hour Pillar (Siju): Represents the hour of birth. It symbolizes fortune related to children and the later years of life (age 46 and beyond).

Since each of the four pillars carries one Heavenly Stem and one Earthly Branch, a Saju chart consists of a total of 8 characters. This is why it is also called "Saju Palja" (四柱八字, Four Pillars, Eight Characters). Analyzing the Five Element distribution and interactions among these 8 characters to determine a person's innate personality, aptitudes, and the flow of their fortune is the essence of Saju Myeongrihak.

Time and the Stems & Branches

When the 24 hours of a day are divided among the 12 Earthly Branches, each time period spans 2 hours. The cycle begins with the Hour of Ja (子時, 23:00–01:00) and ends with the Hour of Hae (亥時, 21:00–23:00). In ancient times, these twelve double-hours were the standard way of telling time, and even today, Saju practitioners convert the birth time into its corresponding Earthly Branch for analysis.

Months are likewise assigned to the 12 Earthly Branches. The cycle starts with In month (寅月, the 1st lunar month) and ends with Chuk month (丑月, the 12th lunar month). An important note: because of the difference between the solar and lunar calendars, the precise Month Pillar must be determined according to the solar terms (Jeolgi, 節氣). For example, In month officially begins only after Ipchun (立春, the Start of Spring), which typically falls around February 4th on the solar calendar.

Direction and the Stems & Branches

The 12 Earthly Branches also correspond to the 12 compass directions. Ja (子) represents due north, Myo (卯) represents due east, O (午) represents due south, and Yu (酉) represents due west. This directional system is used in Pungsu Jiri (Feng Shui) to determine the orientation of home sites and burial grounds. It also serves as a basis for identifying auspicious and inauspicious directions based on an individual's Saju.

Connection to the Seasons

The Five Elements are closely linked to the seasons. Spring is the season of Wood energy, corresponding to the months of In (寅), Myo (卯), and Jin (辰). Summer is the season of Fire, corresponding to Sa (巳), O (午), and Mi (未). Autumn is the season of Metal, corresponding to Sin (申), Yu (酉), and Sul (戌). Winter is the season of Water, corresponding to Hae (亥), Ja (子), and Chuk (丑). Earth governs the last 18 days of each season (the transitional periods), and is associated with the Branches Jin (辰), Mi (未), Sul (戌), and Chuk (丑).

Examining how a person's dominant element harmonizes with the energy of the season in which they were born is an important part of Saju interpretation. For instance, a person with a Wood Day Stem born in spring was born when Wood energy is at its peak, so their elemental energy is strong. Conversely, if that same Wood person were born in autumn, the prevailing Metal energy would exert a controlling influence (Metal overcomes Wood), potentially resulting in a more constrained elemental constitution.