When are the first day, the middle day and the last day?

"Three volts" is a general term for the first, middle and last three volts. The dog days are the highest, wettest and sultry time of the year. Liu Xi, a scholar in the Han Dynasty, recorded in Interpretation of Names: "In troubled times, Geng Jin lies in summer fire. I was afraid of fire, so I fell. " Ban Gu, a historian of the Eastern Han Dynasty, also said in Hanshu: "If you fell, Yin Qi would get up, but you were forced to get up by the sun. Therefore, it is hidden, because of its name. " 12 Fu can be called "Long Summer". Fu is the alternate arrangement of the five elements to the seasons, in which Fu is "earth". Spring, summer, autumn and winter are named by five elements, namely, wood, fire, earth, gold and water. Spring, summer, long summer, autumn and winter are the five seasons in a year. From autumn to winter, aquatic gold, fire gives birth to aquatic wood, and natural circulation. But from summer to autumn, this is not the case. Fire breaks gold, but gold dare not come out. You have to hide for a while. "Latent" is the original meaning of "lying down". [6] [9] [ 14]

Every year, the dog days occur between hot summer and hot summer (from mid-July to mid-August in Gregorian calendar). The so-called "three volts fever" can be divided into the first three volts and the last three volts. According to the traditional calculation method, the time of "Fu" is calculated according to the date of solar terms and calendar, starting from "Geng Day". Among the 24 solar terms, the third day from summer to the future is the first day, the fourth day from summer to the future is the middle day, and the first day after beginning of autumn is the last day, which is always called the third day. The climate in dog days is characterized by "high temperature, high humidity and high fever". The reason for the high humidity in dog days is that the southeast wind blows in dog days, and the Pacific Ocean and Indian Ocean are in the southeast direction. The air is humid, and the humidity of the wind causes the high humidity in the dog days.