What Is the Sixty Gapja? The 60 Stem-and-Branch Combinations That Cycle Through Your Saju

The Sixty Gapja (the sexagenary cycle) is the set of sixty stem-and-branch combinations formed by pairing the ten Heavenly Stems and the twelve Earthly Branches in order. It begins at Gapja (甲子), ends at Gyehae (癸亥), then loops back to Gapja again — one repeating cycle. Because of it, every one of the four pillars in your Saju (Four Pillars of Destiny) — Year, Month, Day, and Hour — is written as one of these sixty combinations. Gwiraedang converts the date and time of your birth into these combinations against a Ten-Thousand-Year (perpetual) calendar to build your chart. It isn't a score that sorts good from bad; it's a reference for self-reflection — a way of reading the grain of time in characters.

Why sixty, of all numbers?

There are ten Heavenly Stems and twelve Earthly Branches, and something interesting happens when you pair them off one by one in order. Gapja (甲子), Eulchuk (乙丑), Byeongin (丙寅)… as both wheels advance one notch at a time together, you land back on the very first Gapja combination after exactly sixty steps. That's because sixty is the least common multiple of ten and twelve.

There's one more rule at work. Both the stems and the branches carry Yang (陽) and Yin (陰) polarity, and when they pair, Yang stems meet only Yang branches, and Yin stems meet only Yin branches. So the Yang stem Gap joins the Yang branch Ja to make Gapja, while the Yin stem Eul meets the Yin branch Chuk to make Eulchuk — and so on. Because of this, only sixty combinations hold, rather than the 120 you might expect. If you're curious about the stems and branches on their own, reading them alongside the Heavenly Stems guide and the Earthly Branches guide makes the pairing logic even clearer.

How is the Sixty Gapja used in Saju?

Each of the four pillars in a Saju chart is written as one of the sixty stem-and-branch combinations. The combination for your birth year becomes the Year Pillar, the month becomes the Month Pillar, the day becomes the Day Pillar, and the hour becomes the Hour Pillar. What all of this conversion rests on is the Ten-Thousand-Year (perpetual) calendar — the manseryeok. It's a calendar that maps solar and lunar dates onto the sixty combinations, with the solar terms and the time boundaries built in precisely, so even on the same day the combination can shift depending on the solar term or the exact hour.

The combination for your birth day — the Day Pillar — is read as the seat that stands for "you" in the chart, so people often look separately at how each of the sixty possible Day Pillars reads as a temperament. Gwiraedang has rendered all sixty Day Pillars, from Gapja to Gyehae, into the language of modern temperament, strengths, and growth points, gathered in its Day Pillar collection. That said, no single Day Pillar reads a whole person — how it all weaves together is something we unpack in How to Read Your Saju.

And what is the nabeum Five Elements?

Laid over the Sixty Gapja is another Five Element classification called the nabeum Five Elements (納音五行). It's a traditional system in which each stem-and-branch combination is given its own distinctive name and element — like Metal-in-the-Sea (海中金), Fire-in-the-Furnace (爐中火), or Wood of the Great Forest (大林木). The curious part is that combinations pair up two at a time to share the same nabeum. For example, Gapja and Eulchuk both fall under Metal-in-the-Sea — gold beneath the ocean.

The nabeum Five Elements views a combination through a different grain than the elements of the stems and branches themselves, so it's a supporting clue you fold in for reference alongside the basic generating and controlling cycles of the Five Elements. Classifications like these are only material for seeing a chart in fuller dimension — none of them, on its own, settles a verdict of good or bad fortune.

FAQ

Does hwangap have anything to do with the Sixty Gapja? Yes — deeply. Hwangap (one's sixtieth year) marks the moment when the stem-and-branch of your birth year has traveled the full Sixty Gapja cycle and returned to where it started. That's why it's written with the characters for "return" (還) and "gap" of gapja (甲) — hwan-gap, the return of the Gapja. The idea that the same combination comes back around only after sixty years — the cyclical structure of the Sixty Gapja — runs all the way into how our culture marks a milestone age.

If I just know the Sixty Gapja, can I read a whole Saju? No. The Sixty Gapja is the basic system for writing down every pillar of a chart, but interpretation doesn't end there. The grain grows clearer when you read it together with other clues: the Ten Gods relationships that each pillar's stem and branch form with your Day Master, the hidden stems tucked inside the branches, and the distribution of the Five Elements. Any confusing terms can be looked up in a Saju glossary. And please hold onto this too — Saju itself isn't a tool that hands you a fixed fate; it's a reference for understanding the temperament you were born with.

The Sixty Gapja in Saju isn't a framework for pronouncing good or bad fortune — it's a reference for reading time in characters and coming to understand yourself. Read it as a mirror, for self-reflection, not fortune-telling.