What a Stem-Branch pair is and why the cycle closes at 60, and where the almanac called the Manse calendar came from.
A Manse calendar is an almanac that sets out, day by day, each year's Stem-Branch pairs (干支) and Solar Terms (節氣). "Manse (萬歲)" means ten thousand years — that is, usable far into the future.
In 1442, under King Sejong of Joseon, the calendrical treatise Chiljeongsan (七政算)was compiled, computing the movements of the sun and moon on the meridian of Hanyang; and in 1782, under King Jeongjo, the royal astronomical bureau published the Cheonseryeok (千歲曆), which calculated a hundred years of calendar days in advance. Revising and continuing that book is the root of what is called the "Manse calendar" today.
Gan (干)means trunk (幹), and ji (支)means branch (枝). Like the trunk and branches of a tree, the 10 Heavenly Stems (天干)and the 12 Earthly Branches (地支)pair up to form a single unit. One such pair is a two-character Stem-Branch pair, and once the pairing has gone round once you have the 60 Gapja.
| Heavenly Stems 天干 | Earthly Branches 地支 | |
|---|---|---|
| Count | 10 | 12 |
| Characters | 甲乙丙丁戊己庚辛壬癸 | 子丑寅卯辰巳午未申酉戌亥 |
| Meaning | The energy of heaven · what is manifest | The places of earth · time and season |
| Structure | 5 elements × 2 (yin and yang) | 4 seasons × 3 stages, 12 months · 12 double-hours |
| What comes with it | Nothing | The 12 zodiac animals, directions, hours |
The element and yin/yang of each character are set out in a table in Yin-Yang & Five Elements · Stems · Branches.
One full round of the 10 stems is ten days (旬, sun). In the old days dates were counted in bundles of ten, which is where the words for the first, middle and last thirds of a month come from. Three sun make one month.
The 12 branches correspond to the twelve months of a yearand the twelve double-hours of a day. The number comes from the observation that the moon waxes and wanes about twelve times in a year.
Stem-Branch pairs are not a notation for Four Pillars charts alone; they were originally a system for numbering time and space.
| Use | Detail |
|---|---|
| Dates | A Stem-Branch pair attached to the year, month, day and hour → the Eight Characters |
| Names of years | The Imjin War (1592, the year Imjin), the Second Manchu Invasion (1636, the year Byeongja), the Gabo Reform (1894, the year Gabo), the Eulsa Treaty (1905, the year Eulsa), the March First Independence Movement (1919, the year Gimi) |
| Age | Hwangap (the 60th birthday) = the year the Stem-Branch pair of one's birth year comes round again after 60 years |
| Directions | 子=north, 卯=east, 午=south, 酉=west (the 12 branches assigned to directions) |
| Order | 甲·乙·丙·丁 = first, second, third, fourth. The "party A and party B" of a contract comes from this |
① The order is always stem first, branch second. There is no way of writing it reversed, as in 午甲.
② Yang pairs only with yang, yin only with yin. That is why there are 60 pairs and not 120. 甲子 (yang+yang) and 乙丑 (yin+yin) exist, but 甲丑 (yang+yin) does not.
③ The pair moves on together, one place at a time. After 甲子 comes 乙丑, not 甲丑.
Turn the 10 stems and the 12 branches together one place at a time, like gears, and at the 60thyou come back to the first pair (甲子). This is because the least common multiple of 10 and 12 is 60. A yang stem meets only yang branches and a yin stem only yin branches, so there are 60 pairs, not 120.
This cycle of 60 is used for the year, month, day and houralike. The 60 Gapja of dates is held to have run without missing a single day for thousands of years; oracle bone inscriptions of the Chinese Shang (商) dynasty already record dates by Stem-Branch pair.
With just the year number, two divisions will give it. The reference point is 1984, which was a 甲子 year.
Trying it with 2026 2026 − 3 = 2023.
The remainder of 2023 ÷ 10 is 3 → the third stem = 丙
The remainder of 2023 ÷ 12 is 7 → the seventh branch = 午
So 2026 is the year 丙午(Byeong-O), the year of the horse.
The Stem-Branch pairs of months, days and hours are not this simple. They need Solar Term entry times and the number of days elapsed since a reference date, so it is quicker to look at the values Manse Calendar Clockcomputes for you.