Please tell me, what is the basis of dog days? Any allusions?

The dog days are the hottest days of the year. "V" means being forced to hide underground. "Three volts" is the general name of the initial, middle and final volts, which appears from mid-July to mid-August in the solar calendar every year. According to the climate law of the lunar calendar in China, predecessors have long stipulated: "The third Geng day after the summer solstice begins with the first day, the fourth Geng day is the first day (the second day), and the first Geng day after beginning of autumn is the last day (the third day), which lasts ten days." In some years, "crouching in the middle" is 20 days, while there are 40 days. According to the textual research of Shu Tong, the lunar calendar and the perpetual calendar, this year is the year of rooster in the solar calendar in 2005. "Three volts" is: July 15, and the tenth day of the Chinese lunar calendar is the first day (also called Fu Tou); July 25, the twentieth day of the lunar calendar, medium volt (two volts); /kloc-The last day of August (dog days) in 0/4 is the first day of July in the lunar calendar. Generally speaking, every volt lasts for ten days, and there are thirty days in three volts. But this year's "year" is "medium volt" (two volts) for 20 days. Therefore, the dog days last for forty days. That is, from the tenth day of the first lunar month to the last day (the twentieth day of the seventh lunar month), it is exactly forty days before and after. The "dog days" are determined according to the ancient "method of keeping records of the sun by the cadres and branches". Every year after the summer solstice, the third Geng Day (referring to the day with the word "Geng" on the trunk and branches) is the beginning period, the fourth Geng Day is the middle period, and the first Geng Day after beginning of autumn is the end period, collectively referred to as the dog days. As the saying goes, "it's hot in dog days." According to the traditional calendar of our country, it is the hottest dog days in summer all year round. Three volts refers to three consecutive periods of initial, intermediate and final voltage. After the summer solstice, the third Geng day is the first day of dive (today is the first day of dive this year), the fourth Geng day is the first day of dive, and the first Geng day after beginning of autumn is the last day of dive, each with 10 days, but in some years it is 20 days, such as this year. Generally speaking, in the "dog days", the average temperature is the highest in the "middle range". Of course, this calculation method of the ancients is not very scientific, and it is not necessarily closely combined with the meteorological reality of that year. The extreme maximum temperature in all parts of the year does not necessarily appear in the "middle volt" or even in the "three volts". But in any case, "dog days" is indeed a hot summer time, and everyone should pay attention to heatstroke prevention and cooling. From the third Geng Day 2 after the first summer solstice 1 to the day before the fourth Geng Day. The third Geng Day was the first day of the first ambush. From the fourth Geng Day after the summer solstice to the first Geng Day after beginning of autumn. The fourth Geng day is the first day of mid-fu, and for beginning of autumn before July of the lunar calendar, mid-fu is 10 day; For the beginning of autumn season after July of the lunar calendar, midsummer is 20 days. A period of time from the first Geng Day after the last autumn in beginning of autumn to the day before the second Geng Day. The second Geng day is designated as going out, that is, the end of the dog days.