What Are Solar Terms (Jie Qi)?
Solar Terms (Jie Qi) are the temporal delimitation standard used in Bazi to divide months and determine fortune cycles. The Bazi system uses the "Jie" nodes among the 24 Solar Terms -- rather than the first day of the lunar month -- as month boundaries. A person's birth month is determined by which Solar Term node follows their birth date, and this is the foundation for calculating the Luck Cycle and assessing the Month Command.
The "Jie" and "Qi" Within the 24 Solar Terms
The 24 Solar Terms are divided into two categories -- "Jie" (, nodes) and "Qi" (, midpoints):
- Jie (Nodes): Beginning of Spring (Li Chun), Awakening of Insects (Jing Zhe), Pure Brightness (Qing Ming), Beginning of Summer (Li Xia), Grain in Ear (Mang Zhong), Minor Heat (Xiao Shu), Beginning of Autumn (Li Qiu), White Dew (Bai Lu), Cold Dew (Han Lu), Beginning of Winter (Li Dong), Major Snow (Da Xue), Minor Cold (Xiao Han)
- Qi (Midpoints): Rain Water (Yu Shui), Spring Equinox (Chun Fen), Grain Rain (Gu Yu), Lesser Fullness (Xiao Man), Summer Solstice (Xia Zhi), Major Heat (Da Shu), End of Heat (Chu Shu), Autumn Equinox (Qiu Fen), Frost Descent (Shuang Jiang), Minor Snow (Xiao Xue), Winter Solstice (Dong Zhi), Major Cold (Da Han)
In Bazi, months are delimited by the Jie nodes (not Qi midpoints):
- After Beginning of Spring (Li Chun) is the Yin month (first lunar month), after Awakening of Insects (Jing Zhe) is the Mao month (second lunar month), and so forth.
Solar Terms and the Month Command
The Earthly Branch of the Month Pillar in a natal chart is determined by the birth Solar Term:
| Solar Term | Month Branch | Lunar Month |
|---|---|---|
| Li Chun – Jing Zhe | Yin | First |
| Jing Zhe – Qing Ming | Mao | Second |
| Qing Ming – Li Xia | Chen | Third |
| Li Xia – Mang Zhong | Si | Fourth |
| Mang Zhong – Xiao Shu | Wu | Fifth |
| Xiao Shu – Li Qiu | Wei | Sixth |
| Li Qiu – Bai Lu | Shen | Seventh |
| Bai Lu – Han Lu | You | Eighth |
| Han Lu – Li Dong | Xu | Ninth |
| Li Dong – Da Xue | Hai | Tenth |
| Da Xue – Xiao Han | Zi | Eleventh |
| Xiao Han – Li Chun | Chou | Twelfth |
Solar Terms and Luck Cycle Commencement
The commencement age is calculated based on the number of days from the birth date to the nearest Solar Term (3 days ≈ 1 year). The precise timing of a Solar Term directly affects the commencement age calculation; a difference of a few days can shift the result by roughly 1–2 years.
The direction of the Luck Cycle progression is either forward or reverse, determined jointly by the birth sex and the Yin-Yang polarity of the year stem:
| Year Stem Polarity | Sex | Direction | Solar Term Counting Method |
|---|---|---|---|
| Yang stems (Jia, Bing, Wu, Geng, Ren) | Male | Forward | Count forward from birth to the next Jie |
| Yang stems (Jia, Bing, Wu, Geng, Ren) | Female | Reverse | Count backward from birth to the previous Jie |
| Yin stems (Yi, Ding, Ji, Xin, Gui) | Male | Reverse | Count backward from birth to the previous Jie |
| Yin stems (Yi, Ding, Ji, Xin, Gui) | Female | Forward | Count forward from birth to the next Jie |
- Forward progression: The Luck Cycle starts from the Month Pillar's Stem-Branch and advances sequentially through the sexagenary order (e.g., Bing Yin → Ding Mao → Wu Chen...).
- Reverse progression: The Luck Cycle starts from the Month Pillar's Stem-Branch and retreats in reverse order (e.g., Bing Yin → Yi Chou → Jia Zi...).
Mnemonic: Yang male and Yin female go forward; Yin male and Yang female go backward.
The Importance of Solar Terms
In Bazi analysis, Solar Terms are an indispensable foundation -- an erroneous Month Pillar Earthly Branch leads to an incorrect Month Command assessment, which in turn affects every subsequent conclusion regarding chart structure, Useful God, and all other analytical dimensions.