Issues involving time and the calendar also were important. Oracle bones suggest that even as far back as the Shang Dynasty the Chinese had been using a luni-solar calendar, whereby both the lunar and solar cycles were important. The lunar months alternated between 29 and 30 days, and an extra intercalary lunar month was introduced every three or four years to match up with the solar year, which the Chinese knew was 365^ days. Through their careful record keeping, they also discovered what was later called the Metonic Cycle, whereby the number of days in 235 lunations were equivalent to 19 solar years that included 7 intercalary months, as well as other cyclical patterns that were even longer. They also had 24 fortnightly periods based on the solar cycle, so that each corresponded to the movement of the Sun by about 15 degrees in longitude on the ecliptic. Note that, like the Babylonians, the Chinese were interested in patterns of events that could be predicted algebraically through the keeping of records, rather than making predictions based on geometric models of nature, which was the strategy used by the ancient Greeks. New calendars have been published regularly in China since 104 bc. The year usually began with the winter solstice. There were minor modifications made to the calendrical system over the centuries until the adoption of the Western-style calendar in 1644.
Was this article helpful?