The 24 Solar Terms in Bazi
Understand the astronomical structure of the twenty-four solar terms, their 15-degree solar-longitude spacing, and which terms change Bazi months.
Overview
The 24 Solar Terms (二十四節氣) divide the Sun’s apparent annual path into twenty-four 15-degree segments. Twelve Jie and twelve Zhongqi alternate through the sequence. In OpenFate Bazi calculation, Li Chun is the Year-Pillar boundary and the twelve Jie start the twelve Month-Pillar segments. Exact term times vary by year and time zone, so a memorized calendar date is only an approximation.
At a glance
- Full cycle
- Twenty-four terms
- Astronomical spacing
- 15 degrees of apparent solar longitude
- Alternating groups
- Twelve Jie and twelve Zhongqi
- Bazi year use
- Li Chun starts the new Year Pillar
- Bazi month use
- Each Jie starts a Month-Pillar segment
- Precision rule
- Use the exact instant for the relevant year
The terms mark equal angular stages of the solar year
The system divides the ecliptic into twenty-four sections of fifteen degrees. Each named term occurs when the Sun reaches the corresponding apparent longitude.
Because the civil calendar and time zones are separate, the local date and clock time of a term can vary from one year or place to another.
- Treat the term as an instant, not only a date.
- Use a documented astronomical source.
Twelve Jie alternate with twelve Zhongqi
The two groups interlace across the year. This distinction matters because a Bazi Month Pillar advances at the Jie boundaries in OpenFate’s contract.
Zhongqi retain calendrical and seasonal significance, but they do not start another Month Pillar in the same calculation.
- Identify the group for each term.
- Do not use every term as a month rollover.
Only specific pillar calculations use the terms as boundaries
Li Chun provides the declared Year-Pillar boundary, while the full set of twelve Jie provides Month-Branch boundaries. The Month Stem is then derived from the Year Stem by the Five Tigers rule.
Day and Hour Pillars use their own continuous-cycle and two-hour rules. The solar terms do not replace those calculations.
- Keep year, month, day and hour algorithms separate.
- Link each symbol to its own rule.
Seasonal names are not direct predictions
Names such as Great Heat, White Dew or Great Snow describe seasonal markers within a historical calendar. They do not diagnose local weather or a person’s chart outcome.
The terms support reproducible calendrical calculation. Any symbolic interpretation remains a separate, contextual traditional layer.
- No weather or fate guarantee from a term name.
- Separate astronomical calculation from interpretation.
Sources and editorial basis
- Hong Kong Observatory: The 24 Solar Terms香港天文台二十四節氣：以太陽視黃經每隔十五度劃分，提供名稱、含義與精確日期時間An official astronomical explanation of the 24 solar terms, their 15-degree divisions along the ecliptic, and the alternating major and minor terms.
- Hong Kong Observatory: The Chinese Agricultural Calendar香港天文台曆表把二十四節氣和公曆、農曆並列，便於區分天文節點與日期標記An official overview of how the Chinese agricultural calendar combines solar and lunar cycles, including months, leap months, and solar terms.
- OpenFate Editorial Methodology產品只把節氣作排盤時間邊界與季節背景；節氣名稱本身不自動生成健康、事件、宜忌或命運結論OpenFate separates deterministic chart calculation, traditional interpretation, and modern editorial explanation.