符天历
Tang · Cao Shiwei (non-official)
Overview
A non-official Tang calendar that dropped the grand epoch and took 660 CE as a near epoch — opening the way for later reform.
Key data
| Item | Detail |
|---|---|
| Period | Tang (non-official) |
| Compiler | Cao Shiwei |
| Innovation | No grand epoch; a near epoch used |
A calendar outside the bureau
The Futian calendar was made by Cao Shiwei and used among the people; the bureau judged it against the old methods and did not adopt it.
Its importance lies in dropping the grand epoch. Traditional calendars reckoned from an “grand epoch” so remote that its year-count ran to millions — cumbersome and error-prone. The Futian took 660 CE as a near epoch and reckoned directly from it, simple and workable.
Influence
The idea was valued by late Tang and Five Dynasties calendrists; Bian Gang’s Chongxuan and others were affected. After the Song the grand epoch was gradually abandoned, and the Futian began it.
That a popular calendar could move the official one shows the debate was not confined to the court.
Compiled and arranged by Chujia Kuang.