Jie and Zhongqi in the Chinese Calendar
Distinguish the twelve Jie from the twelve Zhongqi and learn which exact solar-term instants set Bazi month boundaries.
Overview
The twenty-four solar terms divide the Sun’s apparent annual path into twenty-four equal 15-degree longitude steps. They alternate between twelve Jie and twelve Zhongqi. In Bazi, the twelve Jie—beginning with Li Chun for the Yin month—set the Month-Pillar boundaries; the following Zhongqi describes the middle of that solar month and is important in the Chinese lunisolar calendar, including leap-month rules, but it does not create another Bazi month change. A birth on a term date must be compared with the exact transition instant, not assigned by the civil date alone.
At a glance
- Complete cycle
- 24 terms at 15° solar-longitude intervals
- Alternating sets
- 12 Jie and 12 Zhongqi
- Bazi month change
- Occurs at each exact Jie instant
- Month sequence start
- Li Chun opens the Yin month
- Zhongqi role
- Mid-month marker and lunisolar-calendar input
- Unsafe shortcut
- Using the whole civil term date as a boundary
Jie and Zhongqi alternate along one astronomical cycle
The Sun’s apparent ecliptic longitude advances through twenty-four target positions separated by fifteen degrees. The resulting terms alternate as Jie and Zhongqi through the tropical year.
They are solar markers even though they appear in the Chinese agricultural calendar. A lunar month name or Moon phase does not calculate their transition instant.
- Use solar longitude and an explicit ephemeris.
- Do not derive the terms from lunar dates.
The twelve Jie open the twelve Bazi solar months
Li Chun opens the Yin month, Jing Zhe the Mao month, Qing Ming the Chen month, and the sequence continues through Xiao Han opening the Chou month.
The Month Branch changes at the exact Jie instant. The Month Stem is then derived from the effective Year Stem through the Five Tigers Method, so a boundary calculation must update both parts together.
- Use exact Jie times for Month Pillars.
- Recompute the Month Stem with the new branch.
Zhongqi has a major calendar role without adding a second Bazi month boundary
A Zhongqi follows each Jie near the middle of the solar month. In lunisolar calendar construction, the presence or absence of a principal term helps determine month numbering and leap months.
That function should not be imported as another Month-Pillar switch. Bazi month changes follow the Jie sequence unless a different method is explicitly documented.
- Separate lunisolar month rules from Bazi month pillars.
- Do not change the Month Pillar at every term.
Compare a birth instant with the transition, not the date label
Published calendars often list one civil date for a solar term, but the astronomical crossing occurs at a particular instant. Births before and after that instant on the same date can have different Month Pillars.
Resolve the birthplace time zone and selected time policy, use one ephemeris and state its precision. The canonical sequence is not reversed for Southern Hemisphere births; local seasonal interpretation can be discussed separately.
- Store the term instant and time basis.
- Do not flip the canonical term sequence by hemisphere.
Sources and editorial basis
- Hong Kong Observatory: The 24 Solar Terms香港天文台以黃道每十五度分段說明二十四節氣，並列十二中氣與十二節氣交替排列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香港天文台說明中氣在中國陰陽曆月份與閏月安排中的作用，與太陽節氣日期換算An official overview of how the Chinese agricultural calendar combines solar and lunar cycles, including months, leap months, and solar terms.
- OpenFate Editorial Methodology產品以十二個節的精確交接作八字月柱邊界，中氣保留曆法角色但不新增月柱切換，並揭露星曆與時間基準OpenFate separates deterministic chart calculation, traditional interpretation, and modern editorial explanation.