What is Saju (Korean Four Pillars)?
Saju turns the year, month, day and hour you were born into eight characters, and reads the energies you were born with from them.
Four pillars, eight characters
Saju (四柱) means four pillars: the year, month, day and hour of your birth. Each pillar has a heavenly stem on top and an earthly branch below, so you end up with eight characters in all. A day pillar of gap-ja, for example, has gap (甲) on top and ja (子) below.
The top of the day pillar is you
Of the eight, the top character of the day pillar is called your day master. Saju treats it as you, then reads the other seven by what they are to you: something that supports you, something you pour energy into, or something that presses on you. These relationships are called the ten gods.
Five energies
Every character carries one of five energies: wood, fire, earth, metal or water. Wood feeds fire and water puts it out, so the energies can strengthen or hold each other back. Which ones your eight characters have plenty of, and which are missing, is what the reading builds on.
The year turns at Ipchun, not January 1
The saju calendar splits years and months by the solar terms, not by calendar dates. The year starts at Ipchun, around February 4, and each month turns when a solar term arrives. That is why someone born in January can belong to the previous year's zodiac animal. UPIN finds these boundaries with a solar-term table that matches the Korea Astronomy and Space Science Institute's to the minute.
You can read it without your birth hour
If you don't know the hour, the hour pillar stays empty and the reading uses the other six characters. We never fill in a made-up hour. Knowing it just makes the reading a little finer.
Timing: ten-year and yearly cycles
On top of the eight characters you were born with, saju looks at a big cycle that changes every ten years (daeun) and one that changes every year (seun). UPIN's daily fortune works the same way: it comes from how today's day pillar relates to your day master, so it isn't random.
Saju on UPIN
Saju is a reading, so it doesn't add to the trait cards on your My traits page. Once you save your chart, though, compatibility and the daily fortune are worked out from it.