24 Solar Terms Explained: The Chinese Calendar Behind the Zodiac & BaZi

If you were born in January or early February, there's a good chance your Chinese zodiac sign may be different under the traditional solar system used in BaZi.

Not because the system is flawed — but because most Western sources use Chinese New Year to calculate the zodiac year, while traditional Chinese Astrology uses a different boundary entirely: a precise solar moment called Li Chun, the Start of Spring.

The difference between these two dates can be up to four weeks. And it comes down to an ancient solar framework known as the 24 Solar Terms — the system that actually governs how Chinese Astrology marks time.

30-Second Summary
The 24 Solar Terms (二十四节气) are an ancient Chinese system that divides the Sun's annual path into 24 seasonal markers. They provide the solar framework behind traditional Chinese calendars and play an important role in BaZi (Four Pillars), especially in determining astrological month boundaries.

They also explain why your Chinese zodiac or BaZi calculation may differ from what you see on a Western website — particularly if you were born in January or early February.

What this guide covers:

• Why Li Chun (立春) matters when calculating a BaZi Year Pillar — and how it differs from Chinese New Year
• How the 24 Solar Terms divide the year into 12 Earthly Branch months
• How seasonal Five Element energy relates to the zodiac
• The difference between Jie (节) and Zhongqi (中气)
• Why the Solar Terms remain important in Chinese culture today

Two Conventions: When Does the Zodiac Year Change?

In BaZi and Four Pillars astrology, however, many traditional practitioners use Li Chun (立春, Start of Spring) — the first of the 24 Solar Terms, when the sun reaches 315° of ecliptic longitude — as the boundary for the Year Pillar. The two dates can differ by up to four weeks.

This distinction matters if you were born in January or early February. For example, in 2026, Li Chun occurred on February 4 at approximately 4:02 AM Beijing Time. Because Solar Terms occur at a specific astronomical moment, births close to the boundary should be checked using the local time and location of birth. Under the Li Chun-based BaZi convention, a birth before that moment belongs to the previous Year Pillar (Yi Si, 乙巳 — Year of the Snake); a birth after it belongs to the new one (Bing Wu, 丙午 — Year of the Fire Horse).

⚠️ Born in January or February? Check your accurate sign under both systems →

This article focuses on the classical solar framework — because understanding it is the key to understanding how zodiac timing works at its root in BaZi and traditional calendrical systems.

How Solar Terms Shape the Zodiac Calendar Every Month

In the classical system, each astrological month begins on a Jie (节) Solar Term — a precise astronomical moment when the sun crosses a new 30° segment of its path. Each Jie marks the beginning of a new Earthly Branch month in BaZi — traditionally associated with one of the twelve zodiac animals. These twelve Branches correspond symbolically to the twelve zodiac animals, but an astrological month does not determine your birth-year zodiac sign. The astrological month does not change on the first day of the lunar month; it changes at the Solar Term node.

This is the foundation of traditional monthly zodiac cycles — the actual Solar Term boundaries, not arbitrary calendar dates, determine when one month's energy gives way to the next.

Which Season Is Your Zodiac Energy Strongest?

Each season governed by the Solar Terms corresponds to a dominant Five Element energy. In traditional Chinese astrology, a zodiac sign's seasonal association is one layer of interpretation — but it should not be used on its own to determine whether a person's chart is “strong” or “weak.” In BaZi, seasonal strength is assessed as part of the complete chart, especially in relation to the Day Master.

Earth signs don't belong to a single season — they appear at the end of each season as a transitional phase, when one element's energy is winding down and another is not yet dominant. Think of it as the pause between chapters.

This is a simplified cultural map, not a complete BaZi rule for determining elemental strength. Different traditional schools describe seasonal Earth associations in slightly different ways.

Your birth season places you within one of these elemental rhythms — not as a fixed prediction, but as a mirror reflecting the natural energy you were born into. Find your sign and season →

What Are the 24 Solar Terms?

The 24 Solar Terms (二十四节气, Èrshísì Jiéqì) divide the sun's ecliptic path — its apparent annual journey around the earth — into 24 equal segments of 15 degrees each. The sun takes approximately 15 days to travel each segment, so the Solar Terms fall roughly every two weeks throughout the year.

Unlike the lunar months, which vary in length and drift slightly against the Gregorian calendar, the Solar Terms are anchored to the solar year. Their Gregorian dates are highly consistent — varying by only one or two days from year to year.

The classical mnemonic verse, still memorized by Chinese schoolchildren today:

Spring: 立春雨水惊蛰春分清明谷雨
Start of Spring · Rain Water · Awakening of Insects · Spring Equinox · Clear and Bright · Grain Rain

Summer: 立夏小满芒种夏至小暑大暑
Start of Summer · Grain Buds · Grain in Ear · Summer Solstice · Minor Heat · Major Heat

Autumn: 立秋处暑白露秋分寒露霜降
Start of Autumn · End of Heat · White Dew · Autumnal Equinox · Cold Dew · Frost's Descent

Winter: 立冬小雪大雪冬至小寒大寒
Start of Winter · Minor Snow · Major Snow · Winter Solstice · Minor Cold · Major Cold

All 24 Solar Terms

The 24 Solar Terms are divided into two alternating types: the 12 Jie (节, Nodes) — which mark the start of each astrological month — and the 12 Zhongqi (中气, Central Qi) — which form the twelve “central qi” points alternating with the twelve Jie in the annual solar-term sequence. They are also crucial to the lunisolar calendar's leap-month rule: any lunar month that does not contain a Zhongqi becomes a leap month.

The Most Important Solar Term: Li Chun (立春)

Li Chun — the Start of Spring — is the first Solar Term of the year, occurring when the sun reaches 315 degrees of ecliptic longitude. In 2026, Li Chun fell on February 4 at approximately 4:02 AM Beijing Time.

In BaZi and classical calendrical systems, Li Chun marks the boundary of the Year Pillar. In popular Chinese zodiac culture, the zodiac year is commonly associated with Chinese New Year (Spring Festival). Both conventions are legitimate within their respective contexts — the distinction matters most for people born in January or early February.

The Two Categories: Jie and Zhongqi

The 12 Jie (节, Nodes) — Month Boundaries

The odd-numbered Solar Terms are called Jie — nodes or joints. Each Jie marks the beginning of a new Earthly Branch month in BaZi. This is the boundary used to determine the Month Pillar of a birth chart.

The astrological month does not change on the 1st of the lunar month. It changes at the Jie. A person born on the 28th day of the 7th lunar month, after the Jie of Bai Lu, has their Month Pillar calculated from Bai Lu — not from the 1st of the 8th month.

The 12 Zhongqi (中气, Central Qi) — Leap Month Determinants

The even-numbered Solar Terms are called Zhongqi — central qi. They mark the midpoint of each solar month.

The Zhongqi are the basis of the leap month rule: any lunar month that does not contain a Zhongqi becomes a leap month. This is the mechanism that keeps the Chinese lunisolar calendar synchronized with the solar year.

The Two Solstices: Yin and Yang Turning Points

Two Solar Terms carry special significance in Chinese Astrology because they mark the turning points of Yin and Yang energy:

Dong Zhi (冬至, Winter Solstice) — approximately December 21–23
The longest night of the year. Yin energy reaches its maximum — and at this exact moment, Yang begins to grow. The classical phrase is 冬至一阳生 — “at the Winter Solstice, one Yang is born.” In traditional Chinese cosmology, Dong Zhi marks one of the most important turning points in the seasonal balance of Yin and Yang.

Xia Zhi (夏至, Summer Solstice) — approximately June 21–22
The longest day of the year. Yang energy reaches its maximum — and Yin begins to grow. The classical phrase is 夏至一阴生 — “at the Summer Solstice, one Yin is born.”

These two moments are the anchors of the annual Yin-Yang cycle — the points at which the dominant energy of the year reverses direction.

The Four Li Days and the Four Fen/Zhi Days

The Four Li (四立) — Season Beginnings: Li Chun, Li Xia, Li Qiu, Li Dong
These mark the official start of each season. The day before each Li is called a Si Jue (四绝) day — a “season-ending” day when the old season's energy is exhausted.

The Four Fen/Zhi (四分至) — Equinoxes and Solstices: Chun Fen, Xia Zhi, Qiu Fen, Dong Zhi
These mark the midpoints of each season. The day before each Fen/Zhi is called a Si Li (四离) day — a “season-separating” day when Yin and Yang are in transition.

In traditional almanac and calendrical divination practices, these eight days were sometimes treated as transitional or inauspicious periods for certain activities. This is a traditional belief, not an astronomical or scientific rule. Traditional almanacs sometimes note these days as less favorable for major undertakings. In our monthly forecasts, we present these traditions as cultural and astrological interpretations rather than objective predictions.

Origin and Recognition

The 24 Solar Terms were systematically documented in the Han dynasty, with the Huainanzi (淮南子, compiled around 139 BCE) providing the earliest known complete written record of the system. Earlier texts from the Spring and Autumn and Warring States periods contain references to key seasonal nodes, but the full set of 24 terms was gradually established through the Qin and Han dynasties.

The 104 BCE Tai Chu Li (太初历) calendar reform under Emperor Wu of Han formally incorporated the 24 Solar Terms into the official state calendar and established their astronomical positions — a structure that has remained unchanged for over two thousand years.

In November 2016, UNESCO inscribed the Twenty-Four Solar Terms on the Representative List of the Intangible Cultural Heritage of Humanity. UNESCO describes them as knowledge and practices developed through observation of the Sun's annual motion.