正月本来不是一月

Zhengyue (正月) is ordinarily taken to mean the first month of the year. The two were not always the same thing. This note sets out the san zheng (三正), the three reckonings of the year's beginning that the sources attribute to the Xia, Shang and Zhou, and lists the month each took as its head. The Qin is added to that list: its year opened in the tenth month, and the Qin did not call that month zhengyue — it renamed zhengyue as duanyue (端月) instead, while the four seasons continued to run by the Xia reckoning. The restoration is traced to the Taichu li of 104 BCE, which fixed the head of the year at the first month; that arrangement has held for two thousand years, with four interruptions after it (Wang Mang, the Wei emperor Ming, and twice under the Tang, including Wu Zetian's manufacture of an auspicious date in 698). The note then separates three things the sources keep distinct — the head of the year, the name zhengyue, and the pairing of seasons with months — citing Sima Zhen's commentary on the Shiji, and records Wang Li's doubt as to whether the san zheng can be credited at all. It closes with Shen Kuo's unadopted proposal for a purely solar calendar of months divided by solar terms. The note is descriptive; it contains no predictive claims.

(This preprint has not been peer reviewed.)