Why Ipchun Marks the New Year in Saju: A Complete Guide to the Solar Term Calendar

Three Calendars? The Language of Time That Saju Uses

In daily life, most of us are comfortable moving between the solar calendar and the lunar calendar. Birthdays follow the solar calendar; traditional holidays follow the lunar one. But Saju (Korean Four Pillars astrology) operates on yet another system entirely.

That system is the jeolgi (solar terms), a set of time markers built around the sun's actual position in the sky, specifically where the Earth sits along its orbit around the sun. Unlike the lunar calendar, the solar terms have nothing to do with the phases of the moon.

This is precisely why Saju relies on the solar terms. The sun's position is the most accurate reflection of the seasons and climate, which is to say the flow of natural energy (giun). Because Saju is a tradition that reads a person's temperament and potential within the rhythms of nature, grounding it in the solar terms was the most fitting choice.

What Are the Twenty-Four Solar Terms: The Sun's Map of the Year

The twenty-four solar terms mark the points at which the sun, traveling along the ecliptic (its apparent path across the sky), reaches each successive 15-degree interval. Divide a full 360-degree orbit into 15-degree segments and you get exactly twenty-four.

Six solar terms are assigned to each of the four seasons. Many of their names will be familiar.

• Spring: Ipchun, Usu, Gyeongchip, Chunbun, Cheongmyeong, Gogu
• Summer: Ipha, Soman, Mangjong, Haji, Soseo, Daeseo
• Autumn: Ipchu, Cheoseo, Baengno, Chubun, Hallo, Sanggang
• Winter: Ipdong, Soseol, Daeseol, Dongji, Sohan, Daehan

Among these, the first solar term of each season, namely Ipchun, Ipha, Ipchu, and Ipdong, are collectively called the Sarip (the Four Establishments), meaning the four pillars that open each season. In Saju, the Sarip serve as the core reference points for calculating the month pillar (wolju).

Why Ipchun Is the Saju New Year: The Moment Natural Energy Shifts

Ipchun (Beginning of Spring) is the solar term marking the start of spring. It typically falls around February 4th or 5th each year, and in Saju it is treated as the moment the year pillar (yeonju) turns over.

For example, in 2025 Ipchun arrives in the morning of February 4th. A child born before that moment carries the Saju of 2024, the Year of the Wood Dragon (gabjin). A child born after it belongs to 2025, the Year of the Wood Snake (eulsa). A difference of just a few hours can shift an entire year's designation.

When Saju asks what year you were born, it is not simply asking for a number. It is asking which year's energy you stepped into.

So how is this different from January 1st? January 1st is a boundary drawn by human convenience. Ipchun, on the other hand, is a natural turning point where the sun's position genuinely changes. Because Saju is a tradition built on reading nature's rhythms, it follows nature's own markers.

Ipchun and the Lunar New Year: How They Differ

Many people assume that the Lunar New Year, the first day of the first lunar month, marks the start of the Saju year. It is a very natural assumption. In practice, though, the Lunar New Year and Ipchun fall on different dates almost every year.

Because the lunar calendar is based on the phases of the moon, it does not align neatly with the sun's position. In some years Ipchun arrives before the Lunar New Year; in others it comes after. That gap can make a meaningful difference when reading a Saju chart.

For instance, a child born in the twelfth lunar month may already have crossed into the new year's energy if Ipchun has already passed. Conversely, a child born in early February on the solar calendar is still under the previous year's influence if Ipchun has not yet arrived. Keeping this distinction in mind can also help you read your daily fortune with much greater accuracy.

The Jasi Boundary and Solar Term Timing: Why Precise Time Matters in Saju

Ipchun does not simply begin on "February 4th." It begins at a specific moment on that day. Korea's Korea Astronomy and Space Science Institute publishes the exact entry time for each solar term each year, and that precise moment is what Saju practitioners work with.

Similarly, the day pillar (ilju) does not necessarily change at midnight. In classical Four Pillars tradition, some practitioners place the day boundary at Jasi (the Hour of the Rat), which begins at 11:30 p.m. This question is sometimes called the Jasi boundary issue.

Summary of solar term reference points

• Year pillar reference: the exact moment Ipchun enters (varies each year, usually February 4th or 5th)
• Month pillar reference: the entry moment of each relevant solar term (Ipchun, Gyeongchip, Cheongmyeong, and so on for all twelve month-opening terms)
• Day pillar reference: midnight (00:00) or the traditional Jasi boundary (23:30), depending on the practitioner
• Hour pillar reference: the twelve earthly branches assigned in two-hour blocks

All four reference points need to align before you can establish an accurate set of Four Pillars. Shift just one and the hour pillar changes, which can alter the entire ten-god (sipsin) structure. That is why a practitioner will always ask for your exact time of birth.

In Summary: Understanding Ipchun Changes How You Read Saju

Does the idea of Ipchun as the Saju new year feel a little clearer now? From the perspective of a tradition that grounds itself in natural rhythms, Ipchun is far more than the first day of spring. It is the genuine turning point where one year's energy gives way to the next.

Once you understand that the solar calendar, the lunar calendar, and the solar term calendar all flow on different tracks, it becomes much clearer where your own Saju chart actually begins.

A good Saju reading starts from accurate timing. Knowing the solar terms is the very first step.

If you are curious about the energy at play today, check out today's fortune, organized around the solar term calendar. Simply taking a moment to see which current flows you are moving through can give the day a different feel.