What are the five seasons (五季 Wǔ jì)?

The four seasons of the Northern Hemisphere are winter, spring, summer, and autumn. They are commonly referred to as the cold, dry, hot, and wet seasons. They are based on the four divisions (the two equinoxes and two solstices), where each season covers a phase of three months, a quadrant with each of 90 degrees, and covers one out of four constellations (四象 Si Xiang) the four images.


Although the meteorological conditions of the four seasons may correlate with the four divisions of the sky, there are also seasons based on regions, such as the two (dry and wet seasons), the three (flood, growth, and harvest seasons), and the fifth season.

Seasons are less related to climate than to the grouping of time phases (days/months) in a year. In China, different types of calendars with different divisions were in use, but regardless of their variations, they all used similar concepts.

The division of the ten-month year into 360 days or the twelve-month year into 365 days into five equal parts results in 72/73 days for each phase. For each of the (72/73 days) phases, an element is assigned.

The orders of the (72/73 days) phases after the winter solstice are:
甲子 Jiǎ Zi,  (mu 木), wood,
丙子 Bing Zi, (huo 火), fire
戊子 Wu Zi, (tu 土) earth,
庚子 Geng Zi, (jin 金) metal
壬子 Ren Zi, (shui 水), water.

Aside from many political changes, some significant astronomical and climate changes lead to the adjustment of the seasons and calendars.

In the latest alignment, each of the three months/ a season in a year belongs to one element (wood, fire, metal, or water), and the last 18 days, which is the transition period from one season to another, belong to Earth. In other words, the last four months of the four seasons that belong to Earth are the fifth season.

It is worth mentioning that in the previous (older) alignment, the sixth month (summer) was the fifth season.

Lifecycle of the 5 Elements

Each season/phase belongs to one of the five elements, and in each season, one element is prosperous. The element
wood is strongest in spring,
fire is strongest in summer,
metal is strongest in autumn,
water is strongest in winter, and earth is strongest in the fifth season.

The Ten Heavenly Stems as well as the Twelve Earthly Branches have their own five phases/elements. The element is strongest, 旺 Prosper when the Heavenly Stems or Earthly Branches element matches with the season’s element.

Each element in the Heavenly Stems and the Earthly branches represents a specific phase in a season. The first 12 days of each month are the stronger part, and the last 18 days are the weaker part of the elements.

In the case of the Day Master centric fate calculation method, the Day Master (Heavenly stems element) is strongest when its element is the same as the element in the season (Earthly branches element of the month).

There are five elements and, therefore, five strength indicators. The indicators, from strongest to weakest, are:

旺 Prosper,  相 Strong,  休 Dormant,  囚 In Prison,  死 Death

The ten heavenly stems elements and their representing celestial seasons.

The twelve months/earthly branches representing elements and their solar season.

 

What are the 10 Heavenly Stems (TianGan 天干)?

十天干 Shi Tian Gan - The celestial stems refer in the older system to the uneven division of the five phases (24 hour/5 phases of a day), where each division covers a set of asterisms depicted with the Yang characters and the sub-division; half of each division refers to the opposite side of each phase, depicted with Yin characters, while two of the stems point to the ancient central star. 

The later version refers to the ten phases of the celestial body’s sun, moon, and five planets, each transitioning a specific asterism along the elliptic. These asterisms as markers are known in Chinese as 天干 TianGan, commonly known as the Ten Celestial or Heavenly Stems.

Why is it called the ten stems (天干 TianGan)?

The system of the ten heavenly stems and the twelve earthly branches combined to (干支 GanZi) the sixty-unit cycle predates any verifiable Chinese history; therefore, looking at the system from China's neighbors’ perspective may shed some light to grasp the original meaning of the (八字 BāZì) eight-character system.

Before the sun (was) born, the star* (was) born, meaning that the star was visible before the sun rose. *Star = god, king, ruler, something, or someone with impact or authority.

"On Ok (ock)" means ten arrows, ten directions, ten stems as tribes, ten suns, ten days, or ten gods. Unlike in English, in Chinese, one sun means one day; hence, ten suns are ten days. In short, the ten arrows (pointers) interchangeably called stems (tribes) are used to indicate ten suns or stars.

The ten stem characters 甲 乙 丙 丁 戊 己 庚 辛 壬 癸 are used to count units in the same way as with characters 1 2 3 or A B C. Although the day and year stems are different types of units and have their own astronomical names, the ten stem characters are reused for the hour, day, month, and year, as well as other cycles.

What are these 10 characters of the heavenly stems?

Whatever led to the development of the initial characters, the ten ancient characters are nothing more than visual resemblances of ancient asterisms inside an astronomical constellation. These ten asterisms or characters are part of the four constellations (四象 Sì Xiàng), Turtle, Bird, Tiger, and Dragon, which are used to determine the season’s phases.

What are the 12 earthly branches (Dì Zhī 地支)?

“內經: 天分五氣, 五氣分流，散支于十干” "Nei Jing: The sky is divided by the five Qi (phases), and the branches are scattered in the Ten Stems". Further, “The sky is divided by six poles, and each has its own division (Yang and Ying). A day is divided into six Yang and six Yin therefore, there are 12 branches in a day".

Depending on the perspective, the Earth rotates around its own axis 360 degrees within 24 hours, which is a day, or from the geocentric perspective, the sun takes around 24 hours to revolve around the earth. Either way, the sky (the dome where the stars as ornaments are placed) is divided into six sectors; each of the six divisions has its own Yang/Yin phase. With this, we get 12 sectors in 360 degrees, which are equal to 12 double hours within 24 hours.

Each of the six/twelve divisions/sectors covers a specific asterism along the ecliptic.
While the divisions of the heavenly stems are dynamic, the earthly branches are constant.


What are these 12 characters of the Earthly Branches?

Unlike the heavenly stem characters, which represent asterism around the ecliptic right from the beginning, the twelve characters (the ancient version of the character) of the earthly branches were initially neither asterism nor farming symbols but referred to 12 out of 28 moon phases that morphed as markers into the ecliptic coordinates.

These 12 characters are reused to indicate the 12 Jupiter nodes (year branch, Chinese zodiacs), the 12 months, the 12 moon phases within a month (day branch), and the 12 double hours.

Different regions in China at different times used variations of the 12 characters; therefore, 12 different types of animal symbols were attached to the 12 characters (sectors or phases) to improve their recognisability.



年 Nián: Year

木星 MùXīng: The planet Jupiter is the biggest planet in our solar system; it has a twenty times stronger magnetic field than Earth's. It completes its cycle around the sun every twelve years, which roughly correlates with the 12 lunar cycles on the elliptic path. Each of these 12 cycles has its own astronomical name and is known as (十二次 Shí'èr cì) or (十二分野 Shí'èr fēn yě) Jupiter terms, or nodes.

From the geocentric orbital viewpoint, the direction to which the handle of the natural compass, the Big-Dipper, points when the new moon appears in the same sector (Zodiac) as the planet Jupiter is known as 太歲 Tai Sui, the "Grand Duke of Jupiter” or in short (歲星 Suì xīng), the year star.

Although each 太歲 Tai Sui node/ station has its own astronomical name, which is distinct from the Jupiter nodes, each year-branch is depicted with animal symbols and is recognized easily as the Chinese zodiacs.

When the Earth takes 12 years (twelve times) to revolve the sun, the planet Jupiter revolves the sun once every 11.86 years. This discrepancy causes a shift of the zodiac every 86 years; therefore, the (歲星紀年 Suìxīng jì nián) Jupiter year recording system has been abolished since the later Han dynasty.


月 Yuè: Month

The Month-Branch indicates the earth's position around the sun and the transition of seasons. The Lunisolar calendar year starts in February and is depicted with a tiger. The beginning days of the months are not equal to the first day of the western calendar. Each of the twelve months is also depicted with the same animal symbols used for the years. The month passes one to four of the 28 constellations along the ecliptic every month, which the planet Jupiter culminates in during the year.


月令 Yuè ling: The Month Commander or Month Order.

For event prediction, the month is the starting point to analyze BaZi, the eight-character fate calculation system. In the practical application, the moon phases, the Big Dipper tail, the appearance of the stars, and the climate must be observed.

天 Tiān: Day

The Day Branch indicates the moon's position/ phases around the Earth. The day branches are also depicted with the twelve animal symbols. The day in the month concerns us most in our daily activities; thus, the heavenly stem in the day is taken as the master regarding other elements in the chart; therefore, it is called the 日元 Day Master.

時 Shí: Hour

(十二時辰 Shí'èr shíchén) The Twelve Double-Hours. The Hour-Branch indicates the earth's phase rotation on its own axis. Each Chinese hour consists of two hours; the day is divided into 12 instead of 24 hours. The twelve animal symbols are also used to depict the twelve two-hour blocks.

What is XiaLì (夏曆)?

夏曆 XiàLì The solar, farmers, Chinese, or better known as 萬年曆 WànNiánLì The “Ten Thousand Year Calendar" is a sophisticated astronomical Lunisolar calendar system. Although the evidence indicates that this system predates any remotely assumed Chinese history epoch, it is believed to have been developed during the 夏 Xia Dynasty (2070–1600 BCE); therefore, it is called the (夏曆/夏历 XiaLi) Xia calendar.

The year in this calendar has a division of 24 sectors known as (二十四節氣 ErshiSi JieQi) 24 solar terms; each of the 24 divisions indicates agricultural activities; therefore, (夏历 XiaLi) is also commonly called as (農曆 NóngLì) “Farming calendar”.

The astronomical year of this calendar system begins at midnight on the winter solstice, when the earth is closest to the sun and when the day is shortest around December 21. The calendar year, (元旦 Yuán Dàn) the New Year, begins in the second new moon after the winter solstice.

The months begin at midnight when the new moon phases on the (白經 Bái Jīng) white path, the lunar path on the ecliptic, and (黃經 Huáng Jīng) yellow path, the sun paths on the ecliptic conjunct.

This calendar system in China was used until 1912 and still often mistaken for a pure (陰曆 Yinli) lunar calendar; however, it is a (陰陽曆 Yīn Yáng lì) Yin Yang (Moon/Sun) or, in short, a lunisolar calendar, meaning the months are not based on the lunar phases but the solar terms.


Why is it called the Ten Thousand Year Calendar?

Without getting too much into the details of calendar methods and their individual unit names, the “Ten thousand”, or in numbers, “10.000-year calendar”, is not called as such because the calendar lasts or consists of 10.000 years; rather, it is a reference to one of its units, which is equal to 10.000 years. The largest cycle is 3.600.000 years; this cycle has a division of 360 units, each of which equals 10.000 years.

The smallest unit is known as the (六十花甲 liushi huajia) Sexagenary Cycle or as the (干支 GānZhī) stems-and-branches combination. The alignment of the (十天干 Shi Tian Gan) celestial stems and (十二地支 Shí'èr dìzhī) terrestrial branches in a specific order in six sectors (each of the six sectors consists of 10 stems, or star pointer) will result in 60 combinations; hence, these combinations indicate 60 suns (days) or years.

The sexagenary cycle system initially was used only for days; around the Han dynasty, the year was added, and much later, the month and hours were incorporated.

One sexagenary cycle for years is 60 years,
one cycle for months is 5 years,
one cycle for days is 60 days and
one cycle for the hours is 5 days.

What are the 24 Solar Terms?

二十四節氣 Èr shí sì JiéQì the Twenty-four Solar Terms are 24 seasonal sections of the solar year, or, in other words, the 24 divisions of the sun’s path along the ecliptic. JiéQì is the beginning marker for each of the twelve solar months, and 中氣 ZhongQi marks the middle of the months, which correlates with the twelve Jupiter modes/ terms.

Initially, temporal time was used to determine the phases of the JieQi just by using the shadow length at a specific time. When the sun's shadow was the shortest, this indicated (夏至 xiazhi "summer has arrived"), and when the shadow was the longest, this indicated (冬至 dongzhi "winter has arrived"). 

In later development, the temporal time utilization was changed to fix segments by the division of the ecliptic of the sun into 24 equal sectors. With this newer method, the year begins with the Yin month, and the JieQi marks are the beginning of the sector in which the sun passes.

What are the 12 Life Phases (長生 Cháng Shēng)?

The 12 Life Phases (十二長生, Shí’èr Chángshēng) describe the cyclical rise and decline of elemental energy in the BaZi system. They are primarily used to evaluate the strength of the Day Master within a given seasonal and temporal context.

While the Five Seasons model explains general seasonal strength, the 12 Life Phases provide a more detailed breakdown by dividing seasonal energy into finer stages across all twelve Earthly Branches.

This system uses an analogy of the human life cycle to describe how Qi (energy) is born, grows, peaks, declines, and returns to origin..

Together, the 12 Life Phases describe a complete energetic cycle from emergence to dissolution and renewal. In practical application, they are used to evaluate timing, strength, and interaction of elemental forces within BaZi charts.