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Gapsin Day Pillar (甲申)
— Spring Water, clear water welling up from a spring

Day pillars · 2026.08.25 · 5 min read

The day pillar (ilju 日柱) is the stem-branch pair of the day you were born — the pillar that represents you yourself in Saju (四柱, the Four Pillars). The Gapsin day pillar is the 21st of the sixty Gapja (六十甲子, 60 stem-branch pairs). In this note, we'll lay out its structure — Day Master and day branch, Nayin element (napeum ohaeng 納音五行), Gongmang (空亡, the Void) and Twelve Sinsal (十二神殺, twelve symbolic stars) — using calculations from the Mutal Unnie Saju engine.

What kind of pairing is the Gapsin day pillar?

Picture a tall, straight-growing tree sitting on the early autumn of harvest. Gap Wood (甲木) is the energy of the tree that reaches for the sun first in the forest. It tends to move straight ahead rather than bend, so it's said to suit roles that start and lead things.

Sin Metal (申金) is early autumn, the point where the harvest begins. It's seen as a seat of quick judgment and sharp, capable execution. In Five Elements terms, the Day Master Gap is Wood and the day branch Sin is Metal — a shape in which your seat keeps you on your toes. If the idea of a day pillar is new to you, it's worth reading that first.

What does the Nayin element Spring Water mean?

It means clear water welling up from a spring — spring water rising in the middle of a well. Because it never runs dry and keeps filling back up, it's read as an image of staying power: draw from it and it refills. Well water is also shared by many people, so it's said to be an energy that benefits those around it.

The partner that shares Spring Water is the Eul-yu day pillar. Of the two, Gapsin has a yang stem, so even with the same image it's read as the one that moves first and shows it outwardly.

How do the Day Master Gap and the day branch Sin relate?

The hidden stems of the day branch Sin are Mu, Im and Gyeong, and the main hidden stem is Gyeong (庚). Seen from the Day Master Gap, the main stem Gyeong is the Ten God Indirect Officer.

It's the shape of sitting on an energy that tempers you. There's always a little tension, but in exchange it's seen as a seat that brings out unusual strength in crises and decisive moments. Roles that carry responsibility are said to suit it. If the idea of the Ten Gods is unfamiliar, we recommend starting with the Ten Gods complete guide.

When is the next Gapsin day?

A Gapsin day comes around once every 60 days. Here are the nearest Gapsin days, calculated with the Mutal Unnie Saju engine.

A day carrying the same stem-branch pair as your day pillar is seen as a day when your own energy doubles up. If you jot down how you felt on days like these, your rhythm starts to show. How the daily stem-branch pairs rotate is explained in the story of iljin.

What do the Void branches O·Mi mean?

The sixty Gapja are grouped into six decades (sun 旬) of ten, and the Gapsin day pillar belongs to the Gapsin decade, whose Void branches are O·Mi. The 'empty' characters are O (午) and Mi (未). In terms of a single day, they're the characters of midday and early afternoon, so on days that carry them it's said to be easier to slow your pace by one notch.

Gongmang isn't something to fear; it's closer to a marker telling you where to ease off. How Gongmang works across the whole birth chart is described in detail in Gongmang explained.

What does the Jisal position mean?

Sin is the birth position (saengji 生地) in the Three Harmony Water frame (水局) of Sin·Ja·Jin. That's why the day-branch seat of the Gapsin day pillar is read as Jisal in the Twelve Sinsal.

When a birth-position character falls on the day branch, it's called Jisal. It's a position carrying the power to open a new chapter, so it's read as an energy that comes alive the more you're thrown into unfamiliar settings. The full picture of the twelve sinsal is in The Twelve Sinsal: the complete guide.

Is the day pillar all I need to look at?

The day pillar is two of the Eight Characters. Even with the same Gapsin day pillar, a different birth season (month branch) and birth hour make a completely different chart. A Gap (甲) born in the depths of winter and a Gap (甲) born at the height of summer need different things from the start. So this note introduces the nature of the Gapsin pairing — it isn't a personal Saju reading. If you're curious about your whole birth chart, start with the complete guide to reading Saju.