24 Solar Terms in Saju: Why Your Month Starts on a Jeol

The 24 solar terms (이십사절기 isipsa jeolgi 二十四節氣) are the backbone of saju timing. They divide the sun’s yearly path into 24 equal steps, 15 degrees apart. Twelve of them, called jeol (절 節), open each saju month. That is why your month pillar follows the sun, not the moon, and not the Gregorian calendar.

If you have ever wondered why someone born on February 3 and someone born on February 5 can have different saju years, the answer is here. The line between them is Ipchun, the “start of spring” term.

Let’s walk through what the solar terms are, how saju uses them, and what to check if you were born near one.

What the solar terms are

The solar terms began in China as a way to follow the seasons for farming. Each term marks a point along the ecliptic, the sun’s apparent path through the sky, spaced 15 degrees apart. Twenty-four steps make a full circle.

The system spread across East Asia, including Korea. Korean almanacs still list every term, and many of the names are part of everyday Korean: people talk about 입춘 ipchun at the start of spring and 동지 dongji at the winter solstice.

In 2016, UNESCO inscribed “The Twenty-Four Solar Terms, knowledge in China of time and practices developed through observation of the sun’s annual motion” on its Representative List of the Intangible Cultural Heritage of Humanity. The listing is China’s, and it describes the terms as a cycle that begins with the Beginning of Spring and ends with the Greater Cold. That same starting point, Beginning of Spring, is where the saju year begins.

Jeol and jung: two kinds of terms

The 24 terms alternate between two roles:

Jeol (절 節): twelve “node” terms that start a month.
Junggi (중기 中氣): twelve “middle” terms that sit at the midpoint of a month. The winter solstice is one of these.

Saju uses the twelve jeol as month boundaries. When the sun reaches a jeol, the month branch changes, and with it the month pillar.

The 12 jeol and the saju months

Here are the twelve jeol, the Korean readings and the month branch each one opens. Dates are approximate and can shift by a day from year to year.

Jeol	Korean	Meaning	Around	Opens month of
立春	입춘 ipchun	Start of spring	Feb 4	寅 in, Tiger
驚蟄	경칩 gyeongchip	Insects awaken	Mar 6	卯 myo, Rabbit
清明	청명 cheongmyeong	Clear and bright	Apr 5	辰 jin, Dragon
立夏	입하 ipha	Start of summer	May 6	巳 sa, Snake
芒種	망종 mangjong	Grain in ear	Jun 6	午 o, Horse
小暑	소서 soseo	Minor heat	Jul 7	未 mi, Goat
立秋	입추 ipchu	Start of autumn	Aug 8	申 sin, Monkey
白露	백로 baengno	White dew	Sep 8	酉 yu, Rooster
寒露	한로 hallo	Cold dew	Oct 8	戌 sul, Dog
立冬	입동 ipdong	Start of winter	Nov 7	亥 hae, Pig
大雪	대설 daeseol	Major snow	Dec 7	子 ja, Rat
小寒	소한 sohan	Minor cold	Jan 6	丑 chuk, Ox

Notice that the Tiger month, not the Rat month, comes first. The saju year opens with spring, so 寅 in (Tiger, wood) leads, and the Ox month in January closes the old year.

Why saju follows the sun instead of the moon

People often call saju “lunar,” but the pillars mostly run on the solar terms. The lunar calendar still matters in Korean life. Seollal (설날, Lunar New Year) and Chuseok are lunar holidays, and many families record birthdays in lunar dates. But lunar months drift against the seasons, and the calendar needs leap months to stay in step.

The solar terms don’t drift. Each jeol sits at the same point of the sun’s path every year. For a system that reads seasons as elements (wood for spring, fire for summer, metal for autumn, water for winter, with earth in the transitions), a sun-based month makes sense. A Tiger month always feels like early spring.

So:

Year pillar changes at Ipchun, around February 4.
Month pillar changes at each of the twelve jeol.
Day pillar follows the continuous 60-day cycle.
Hour pillar follows the twelve double-hours of the day.

If you were born near a solar term

The exact moment of a jeol can fall at any hour. A birth a few hours before the term belongs to the old month; a birth a few hours after belongs to the new one. Around Ipchun, the year changes too.

What to do:

Check your birth date and time. Early February, and the first week of any month, deserve a second look.
Use a proper manseryeok (만세력 萬歲曆, a saju almanac). It stores the exact time of each term instead of assuming a fixed date.
Confirm the time zone. Korean clock time has changed several times in history, which can move a birth across a term boundary.
Don’t panic about “the wrong year.” Many people learn their ddi (띠, zodiac animal) from Lunar New Year or January 1. That’s fine for casual talk. Your saju chart simply uses a different line.

A Korean custom at Ipchun

Ipchun is also a small household celebration in Korea. Traditionally, families write short blessings for the new spring and post them on walls or door frames. These are called ipchunchuk (입춘축) and go by several other names. It’s a nice reminder that in Korea, the solar terms aren’t just astronomy. They are part of how the year feels.

FAQ

How many solar terms does saju use?

All 24 exist in the calendar, but saju month pillars use the twelve jeol (節), the terms that open each month. The other twelve, the junggi, mark month midpoints. Ipchun, around February 4, is the most important jeol because it starts both the Tiger month and the saju year.

Why is my saju year different from my zodiac year?

Your zodiac year in casual conversation often follows Lunar New Year or even January 1. The saju year changes at Ipchun, around February 4. If you were born between January 1 and Ipchun, your saju year pillar belongs to the previous year. Neither view is wrong; saju just uses the solar term as its boundary.

Did UNESCO recognize the 24 solar terms?

Yes. In 2016 UNESCO inscribed “The Twenty-Four Solar Terms” on the Representative List of the Intangible Cultural Heritage of Humanity, as an element nominated by China. The listing honors the terms as living knowledge about time and seasons. It is a cultural recognition, not an endorsement of saju or any fortune-telling practice.

Do solar term dates change every year?

Slightly. Each term is defined by the sun’s position, so its calendar date can move by about a day, and its exact time changes every year. That’s why saju tools use almanac tables rather than fixed dates. If your birthday is within a day of a jeol, check the exact time.

Try it with the Moon Rabbit

Born close to a solar term? The free pro chart uses exact term times, so you can see which month and year pillar you really have. For a quick, friendly overview of your chart, grab a free saju card from the Moon Rabbit.

Saju is a cultural tradition, not a science. SajuBunny readings are for fun and self-reflection, not professional advice.

Sources

For fun and self-reflection. Saju is a traditional way of looking at yourself, not a prediction or professional advice.