On the Four Seasons and Solar Terms
Original Text
卦气正月为泰，天气下降，当为雨水；二月大壮，雷在天上，当为惊蛰，先雨水而后惊蛰，亦宜也，惊蛰者，万物出乎震，震为雷也；清明者，万物齐乎巽，巽为风也，巽洁齐而曰清明，清明乃洁齐之义；谷雨三月中，自雨水后土膏脉动，至此又雨，则土脉生物，所以滋五谷之种也；小满四月中，先儒云：小雪后阳一日生一分，积三十日，生三十分而成一昼，为冬至，小满后阴生亦然。至若三月中谷雨，五月中芒种，此二气独指谷麦言，谷必原其生之始，谷种于春，得木之气，残于秋，金克木也；麦必要其成之终，麦种于秋，得金之气，成于夏，火克金也；六月节小暑，六月中大暑，六月中暑之极，故谓大，然未至于大则犹为小也；七月中处暑，七月暑之终，寒之始，大火西流，暑气于是乎处矣，处者，隐也，藏伏之义也；白露八月节，寒露九月节，秋木属金，金色白，金气寒白者，露色，寒者，露之气，先白而气始寒，固有渐也，九月中霜降露寒，始结为霜也；立冬后曰小雪、大雪，寒气始于露，中于霜，终于雪，霜之前为露，霜由白而始寒，霜之后为雪，雪由小而至大，皆有渐也；至小寒大寒，《幽风》云：「一之日徉发，二之日栗烈」，徉发风寒，故十一月之馀为小寒，栗烈气寒，故十二月之终为大寒也。
大抵合而言之，上半年主长生，曰雨曰雷曰风，皆生之气，下半年主生成，曰露曰霜曰雪，皆成之气。下半年言天时，不言农时，农时莫急于春夏也。
Interpretation
In the first month of the lunar calendar according to the theory of hexagram - qi, it corresponds to the hexagram Tai. At this time, the celestial qi descends, and it should be the Rain Water (one of the 24 solar terms). In the second month, it corresponds to the hexagram Da Zhuang. With thunder above the sky, it should be the Awakening of Insects. Having Rain Water before the Awakening of Insects is also appropriate. The Awakening of Insects means that all things emerge from the influence of Zhen. Zhen represents thunder. For the Pure Brightness, all things are in an orderly state under the influence of Xun. Xun represents wind. Xun implies cleanliness and orderliness, so it is called Pure Brightness, which means cleanliness and order. Grain Rain falls in the middle of the third month. Since the Rain Water, the fertile soil has shown signs of activity. When it rains at this time, the soil can nurture living things and moisten the seeds of the five grains. Lesser Full falls in the middle of the fourth month. The previous scholars said that after Lesser Snow, the yang qi grows by one - unit each day. After thirty days, it accumulates to thirty units and forms a full - day cycle, which is the Winter Solstice. Similarly, after Lesser Full, the yin qi begins to grow. As for Grain Rain in the middle of the third month and Grain in Ear in the middle of the fifth month, these two solar terms specifically refer to grains and wheat. Grains must be traced back to their origin. Grains are sown in spring and receive the qi of wood. They wither in autumn because metal overcomes wood. Wheat must be considered in terms of its completion. Wheat is sown in autumn and receives the qi of metal. It matures in summer because fire overcomes metal. Lesser Heat is the solar term at the beginning of the sixth month, and Greater Heat is in the middle of the sixth month. The heat reaches its peak in the sixth month, so it is called Greater Heat. Before reaching the peak, it is still Lesser Heat. End of Heat falls in the middle of the seventh month. It marks the end of the hot season and the beginning of the cold season. As the Big Dipper's handle points westward, the heat gradually subsides. "Chu" (处) means hiding and the meaning of concealing and lying dormant. White Dew is the solar term at the beginning of the eighth month, and Cold Dew is at the beginning of the ninth month. In autumn, wood is associated with metal. The color of metal is white, and the qi of metal is cold. White is the color of the dew, and cold is the nature of the dew. First, the dew is white, and then its qi starts to turn cold, which is a gradual process. Frost's Descent is in the middle of the ninth month. When the dew is cold, it begins to form frost. After the Beginning of Winter, there are Lesser Snow and Greater Snow. The cold qi starts with the dew, reaches a medium level with the frost, and reaches its peak with the snow. Before the frost, there is dew. The frost starts from being white and then turns cold. After the frost, there is snow. The snow gradually increases from small to large, all showing a gradual process. As for Lesser Cold and Greater Cold, as the poem in "The Odes of Bin" says: "In the first month, the wind blows sharply; in the second month, the cold is severe." The sharp wind in the eleventh month is the so - called Lesser Cold, and the severe cold in the twelfth month is the so - called Greater Cold.
Generally speaking, in the first half of the year, the main theme is growth. Rain, thunder, and wind all represent the energy of growth. In the second half of the year, the main theme is maturation. Dew, frost, and snow all represent the energy of maturation. When talking about the second half of the year, we refer to the natural timing rather than the agricultural timing, because there is nothing more urgent than spring and summer in agricultural activities.