How the Sixty-Year Cycle Is Formed
In this post, I will explain how the Ten Heavenly Stems and Twelve Earthly Branches combine to create the sixty Stem-Branch pairs.
You may have heard that 2026 is the Year of the Red Horse. But where does that name actually come from?
The answer goes back to a pairing system that has been used for thousands of years. Byeong (병, 丙) is a Fire Stem — and Fire is traditionally associated with the color red. O (오, 午) is the Branch that corresponds to the Horse. Put them together: Red Horse.
This kind of name — one Heavenly Stem paired with one Earthly Branch — is called a Stem-Branch pair. The complete set of sixty such pairs is known as the Sixty-Year Cycle, or Yuksip Gapja (육십갑자, 六十甲子).
2024 was Gapjin (갑진, 甲辰). 2025 was Eulsa (을사, 乙巳). 2026 is Byeongo (병오, 丙午). Each year has its own name, and those names cycle through sixty positions before starting over.
Why Sixty?
The Ten Heavenly Stems run in order and repeat:
Gap (갑, 甲) → Eul (을, 乙) → Byeong (병, 丙) → Jeong (정, 丁) → Mu (무, 戊) → Gi (기, 己) → Gyeong (경, 庚) → Sin (신, 辛) → Im (임, 壬) → Gye (계, 癸) → Gap again
The Twelve Earthly Branches also run in order and repeat:
Ja (자, 子) → Chuk (축, 丑) → In (인, 寅) → Myo (묘, 卯) → Jin (진, 辰) → Sa (사, 巳) → O (오, 午) → Mi (미, 未) → Sin (신, 申) → Yu (유, 酉) → Sul (술, 戌) → Hae (해, 亥) → Ja again
Think of two gears turning together — one with ten teeth, one with twelve. For both to return to their starting position at the same time, they need to turn through the smallest number divisible by both 10 and 12. That number is 60.
So the first pair is Gapja (갑자, 甲子) and the sixtieth is Gyehae (계해, 癸亥). After that, the whole sequence starts again from Gapja.
The Complete Sixty-Year Cycle
| No. | Stem-Branch Pair | No. | Stem-Branch Pair | No. | Stem-Branch Pair |
|---|---|---|---|---|---|
| 1 | Gapja (갑자, 甲子) | 21 | Gapsin (갑신, 甲申) | 41 | Gapjin (갑진, 甲辰) |
| 2 | Eulchuk (을축, 乙丑) | 22 | Eulyu (을유, 乙酉) | 42 | Eulsa (을사, 乙巳) |
| 3 | Byeongin (병인, 丙寅) | 23 | Byeongsul (병술, 丙戌) | 43 | Byeongo (병오, 丙午) |
| 4 | Jeongmyo (정묘, 丁卯) | 24 | Jeonghae (정해, 丁亥) | 44 | Jeongmi (정미, 丁未) |
| 5 | Mujin (무진, 戊辰) | 25 | Muja (무자, 戊子) | 45 | Musin (무신, 戊申) |
| 6 | Gisa (기사, 己巳) | 26 | Gichuk (기축, 己丑) | 46 | Giyu (기유, 己酉) |
| 7 | Gyeongo (경오, 庚午) | 27 | Gyeongin (경인, 庚寅) | 47 | Gyeongsul (경술, 庚戌) |
| 8 | Sinmi (신미, 辛未) | 28 | Sinmyo (신묘, 辛卯) | 48 | Sinhae (신해, 辛亥) |
| 9 | Imsin (임신, 壬申) | 29 | Imjin (임진, 壬辰) | 49 | Imja (임자, 壬子) |
| 10 | Gyeyu (계유, 癸酉) | 30 | Gyesa (계사, 癸巳) | 50 | Gyechuk (계축, 癸丑) |
| 11 | Gapsul (갑술, 甲戌) | 31 | Gabo (갑오, 甲午) | 51 | Gabin (갑인, 甲寅) |
| 12 | Eulhae (을해, 乙亥) | 32 | Eulmi (을미, 乙未) | 52 | Eulmyo (을묘, 乙卯) |
| 13 | Byeongja (병자, 丙子) | 33 | Byeongsin (병신, 丙申) | 53 | Byeongjin (병진, 丙辰) |
| 14 | Jeongchuk (정축, 丁丑) | 34 | Jeongyu (정유, 丁酉) | 54 | Jeongsa (정사, 丁巳) |
| 15 | Muin (무인, 戊寅) | 35 | Musul (무술, 戊戌) | 55 | Muo (무오, 戊午) |
| 16 | Gimyo (기묘, 己卯) | 36 | Gihae (기해, 己亥) | 56 | Gimi (기미, 己未) |
| 17 | Gyeongjin (경진, 庚辰) | 37 | Gyeongja (경자, 庚子) | 57 | Gyeongsin (경신, 庚申) |
| 18 | Sinsa (신사, 辛巳) | 38 | Sinchuk (신축, 辛丑) | 58 | Sinyu (신유, 辛酉) |
| 19 | Imo (임오, 壬午) | 39 | Imin (임인, 壬寅) | 59 | Imsul (임술, 壬戌) |
| 20 | Gyemi (계미, 癸未) | 40 | Gyemyo (계묘, 癸卯) | 60 | Gyehae (계해, 癸亥) |
After Gyehae (계해, 癸亥), the sequence returns to Gapja (갑자, 甲子) and begins again.
Not Just Years — Days and Hours Too
Most people today encounter the Sixty-Year Cycle through birth years and zodiac animals. But in traditional calendars, the same system was applied to months, days, and hours as well.
A person's birth moment was recorded as four separate Stem-Branch pairs — one for the year, one for the month, one for the day, and one for the hour. These four pairs are called the Year Pillar, Month Pillar, Day Pillar, and Hour Pillar. Together, they form the Four Pillars — the foundation of Saju.
Individual days also carried Stem-Branch names. If today was a Gapja day, tomorrow would be Eulchuk, the day after Byeongin — cycling through all sixty before returning to Gapja. The name assigned to each day was called the Iljin (일진, 日辰), and people consulted it when planning farming, ceremonies, and important events.
The Stem-Branch pairs weren't invented as fortune-telling symbols. They started as a practical calendar — a coordinate system for locating moments in time.
Why the Sixtieth Birthday Matters: Hwangap
Here's something that gives me pause every time I think about it.
The Stem-Branch pair of your birth year only comes back around once — sixty years later. Someone born in a Gapja year won't see another Gapja year until they turn sixty. That return is called Hwangap (환갑, 還甲) — literally, "the return of Gap." It's also known as Hoegap (회갑) or Jugap (주갑), all carrying the same meaning: a full cycle completed.
Today, sixty feels like the beginning of a new chapter. People are still working, traveling, raising grandchildren. But in earlier times, reaching sixty was genuinely rare. Life was shorter, medicine was limited, and simply surviving the risks of illness, childbirth, poverty, and war was not something anyone could take for granted.
So when someone reached Hwangap, the whole family gathered. Children prepared a feast. Relatives and neighbors came together to celebrate. It wasn't just a birthday — it was the recognition that this person had lived through an entire turning of the calendar. That deserved to be honored.
The number hasn't changed. But the weight of it was very different then.
Time as a Cycle, Not a Line
We're used to thinking of time as a straight line — 2024, 2025, 2026, always moving forward, never looping back. The numbers just keep going.
The Sixty-Year Cycle holds a different view. Time moves in cycles. The sequence begins, runs through sixty positions, and returns to its starting point. Then it begins again.
But this doesn't mean the same thing simply repeats. A new Gapja year belongs to different people, a different world, a different age. Spring comes back every year, but no two springs are the same. The names return — the moments don't.
What the cycle suggests is that within the constant forward movement of time, there are rhythms. Patterns that recur. A structure underneath the surface of passing days.
And knowing that structure — knowing where you stand within it — is part of what Saju is trying to offer.
