Lunar-phase terms in Western Zhou bronze inscriptions

西周金文月相 Western Zhou · c. 11th century–771 BCE

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Overview

The lunar-phase terms in Western Zhou bronze inscriptions are the core material for the calendar and day-reckoning of the period, and a key to Western Zhou chronology.

Key data

ItemDetail
CarrierWestern Zhou bronze inscriptions
Core termsChuji, jishengba, jiwang, jisiba
UseCombined with month and sexagenary day to form a complete date formula
StatusOne of the four main supports of Western Zhou chronology

The date formula

The usual Western Zhou formula is “year + month + lunar phase + sexagenary day,” as in “in the first year of the king, first month, jishengba, dinghai.” The phase term divides one lunation into segments.

The formula is peculiar to the Western Zhou and fell out of use after the Eastern Zhou.

The four-phase theory

The meaning of the four terms has long been disputed. One widely held view quarters the lunation: chuji covers the first to seventh or eighth day, jishengba the eighth or ninth to the fifteenth, jiwang the fifteenth or sixteenth to the twenty-second or twenty-third, and jisiba the twenty-third to the month’s end.

Another view holds that each term marks a single fixed day rather than a span. The two have not been reconciled.

Why it matters

Bronze vessels are usually dated by this formula together with their form and ornament. If the phase terms could be fixed exactly, Western Zhou chronology could be precise to the year; otherwise only a range can be given.

This is one reason Western Zhou chronology has long resisted settlement — the disagreement lies not in the material but in the reading of these few words.

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Compiled and arranged by Chujia Kuang.