24 Solar Terms (Jeolgi) | Saju Glossary

The 24 Solar Terms (Jeolgi) divide the year into 24 segments based on the Sun's ecliptic longitude. In Saju, the Month Pillar (Wolju) is determined not by the Western calendar or the lunar calendar, but by these solar terms. This is one of the most commonly misunderstood aspects of Saju calculation. For example, Ipchun (Start of Spring) usually falls around February 4. In Saju, the distinction between a January birth and a February birth is based on this moment, not the calendar date. If born before Ipchun, the person belongs to the previous year's 12th month (Chuk month); if born after, they belong to the 1st month (In month). Key solar terms and their corresponding Saju months: ● Ipchun (around Feb 4) → In month (1st month) begins ● Gyeongchip (around Mar 6) → Myo month (2nd month) begins ● Cheongmyeong (around Apr 5) → Jin month (3rd month) begins ● Ipha (around May 6) → Sa month (4th month) begins ● Mangjong (around Jun 6) → O month (5th month) begins ● Soseo (around Jul 7) → Mi month (6th month) begins ● Ipchu (around Aug 8) → Sin month (7th month) begins ● Baengno (around Sep 8) → Yu month (8th month) begins ● Hallo (around Oct 8) → Sul month (9th month) begins ● Ipdong (around Nov 7) → Hae month (10th month) begins ● Daeseol (around Dec 7) → Ja month (11th month) begins ● Sohan (around Jan 6) → Chuk month (12th month) begins For accurate Saju calculation, it is important to verify the exact time (year, month, day, hour, minute) of each solar term transition. The reason solar terms are so important in Saju is that they reflect actual energy changes in nature. The Western calendar is an artificial system created for convenience, and the lunar calendar is based on the phases of the moon, but solar terms measure real climatic changes driven by the relationship between the sun and the earth. Since Saju is the "study of energy," it is logically natural to use solar terms — the most accurate reflection of energy shifts — as the standard. People born near a solar term boundary require special attention in practice. For example, someone born on February 3 may have an entirely different Year Pillar and Month Pillar depending on whether Ipchun falls on February 3 or 4 that year, and what the exact hour and minute of the transition is. If born before Ipchun, the previous year's Stem-Branch combination applies, which can even change the person's zodiac animal. This is why the common question arises: "I was born in late January — why does my zodiac show the previous year's animal?" Among the 24 solar terms, the 12 that serve as Month Pillar boundaries are called "Jeol" (nodes), while the remaining 12 are called "Gi" (breaths). A Jeol marks the start of a new month, and a Gi marks the midpoint when that month's energy reaches its peak. For instance, Ipchun (a Jeol) begins the In month, while Usu (a Gi) is the point when the In month's energy is at its zenith. DESTIGER applies astronomical precision to its solar term calculations, reflecting transition times down to the exact minute. When a user enters their birth date and time, DESTIGER automatically determines the solar term boundary at that moment and derives the correct Month Pillar. This ensures that even people born on a solar term boundary receive error-free Saju analysis, preventing the Month Pillar miscalculations that commonly occur in manual computation.