Jieqi

Chinese months follow the phases of the moon. The solar-based agricultural calendar is made up of twenty-four points called jieqi. They are essentially seasonal markers to help farmers decide when to plant or harvest crops, as the lunisolar calendar is for obvious reasons unreliable in this respect.

The term Jiéqì is usually translated as "Solar Terms" (lit. Nodes of Weather). Each is the instant when the sun reaches one of twenty-four equally spaced points along the ecliptic, including the solstices and equinoxes, positioned at fifteen degree intervals. In the table below, these measures are given in the standard astronomical convention of ecliptic longitude, zero degrees being positioned at the vernal equinox point. Because the calculation is solar-based, these jiéqì fall around the same date every year in solar calendars such as the Gregorian Calendar, but do not form any obvious pattern in the Chinese calendar. The dates below are approximate and may vary slightly from year to year due to the intercalary rules of the Gregorian calendar. Jiéqì are published each year in farmers' almanacs. Chinese New Year is usually the new moon day closest to lìchūn. Each calendar month under the heading "M" contains the designated jiéqì called a principle term, which is an entry into a sign of the zodiac, also known as a cusp. Here term has the archaic meaning of a limit, not a duration. In Chinese astronomy, seasons are centered on the solstices and equinoxes, whereas in the standard Western definition, they begin at the solstices and equinoxes. Thus the term Beginning of Spring and the related Spring Festival fall in February, when it is still very chilly in temperate latitudes in the Northern Hemisphere.

Note: The third jieqi was originally called (qizhe) but renamed to (jingzhe) in the era of the Emperor Jing of Han (hanjingdi) to avoid writing his given name qi.