PHENOLOGY LOGIC

Phenology Logic

Five days per pentad, three pentads per term; 72 pentads weave the year's seasonal narrative

Core Concepts · Pentad-Term-Seasonal Term Hierarchy

Five Days per Pentad

Observe nature in five-day units; "pentad" means "awaiting," precisely timing earth's changes. The 365.25-day year divides into 72-73 pentads, forming the most delicate seasonal scale.

Three Pentads per Term

Three pentads (15 days) form one term. Each term divides into first, second, and third pentads, revealing climate's progressive stages. 24 terms × 3 pentads = 72 pentads, completing the annual narrative.

Phenological Observation

Observe sky (wind, frost, rain, snow), animals (birds, insects, fish), and plants (blooms, falling leaves). Concrete, tangible "phenology" anchors abstract time. Ancients wove daily rhythms; moderns can translate this into observational calendars.

Evolution of Phenology System

Germination Period (Pre-Qin)

Scattered phenological records, not yet systematized

The Book of Songs and Xia Xiaozheng contain scattered phenological descriptions like "Fire Star sets in the seventh month" and "Yáo blooms in the fourth month," reflecting early agricultural awareness of natural rhythms, but not yet a standardized "five days per pentad" system.

Method: Oral tradition and poetic documentation

Systematization Period (Qin-Han)

Yizhoushu established the 72-pentad framework

First articulation of "five days per pentad, three pentads per term" structure. Each term assigned three pentad phenomena, such as "Spring Begins: 1st pentad east wind thaws, 2nd pentad hibernating insects stir, 3rd pentad fish surface under ice," forming a standardized 24 terms × 3 pentads narrative template.

Technical support: Gnomon shadow measurement + phenological observation logs

Maturity Period (Han to Yuan)

Huainanzi and Liji refined pentad descriptions

Building on Yizhoushu, further refined pentad phenomena with detailed flora, fauna, and meteorological features, enhancing regional adaptability. Huainanzi integrated phenology with yin-yang and Five Phases theory, deepening philosophical dimensions. Liji linked pentads to ritual and governance, becoming a state administration tool.

Supporting tools: Monthly ordinance charts and phenology handbooks circulated among populace

Culmination Period (Yuan to Qing)

Yueling Qishier Hou Jijie solidified as canonical text

Wu Cheng's Yuan-era Yueling Qishier Hou Jijie synthesized centuries of phenological knowledge, providing precise pentad explanations and life guidance for each pentad, becoming the authoritative reference. During Ming and Qing dynasties, phenological knowledge spread widely via agricultural and almanac texts, embedding "farm by pentads" and "nourish life by pentads" traditions into daily practice.

Dissemination: Woodblock printing popularized phenological knowledge

Authoritative Literary Sources

Yizhoushu · Shixun Jie

Warring States to W. Han

First systematic documentation of the 72-pentad system, establishing "five days per pentad, three pentads per term" structure.

Origin text of systematized phenology

Yueling Qishier Hou Jijie

Yuan Dynasty (Wu Cheng)

Comprehensive synthesis of historical phenology with detailed annotations for each pentad, such as "Spring Begins, 1st pentad: East wind thaws ice frozen in winter, dispersing with spring breeze," becoming the standard reference.

Most authoritative 72-pentad annotated edition

Huainanzi · Tianwen Xun

Western Han

Integrates phenology with yin-yang, Five Phases, and astronomy-calendrics, elucidating the cosmological and philosophical logic behind pentads, e.g., "When spring qi arrives, plants grow."

Exemplar of philosophical phenology

Liji · Yueling

Warring States to Han

Links pentads to ritual and governance, stipulating "In the first month of spring, east wind thaws, hibernating insects stir... the emperor resides in Qingyang's left chamber," forming a state administration timetable.

Model of phenology in state governance

Xia Xiaozheng

Attributed to Xia Dynasty

China's earliest extant phenological text, recording monthly flora, fauna, and celestial changes like "In the first month hibernation ends, fish surface under ice," providing a prototype for later phenology systems.

Source text of phenological observation

Relevant Shijing passages

W. Zhou to Spring-Autumn

Numerous poems referencing phenology, such as "Fire Star sets in the seventh month, in the ninth month distribute clothes" (Binfeng · July) and "Reeds luxuriant, white dew turns to frost" (Qinfeng · Reeds), showcasing poetic folk phenological observation.

Poetic phenological records

Phenology Manifesto

Between thawing ice and birdsong, we record the season's breath; between frost's fall and spring's stir, we hear time's footsteps. The 72 pentads aren't cold numbers but rhythms resonating life with heaven and earth. Let us reclaim the ancients' observant gaze and, in the delicacy of five-day intervals, rediscover life's cadence synchronized with nature.