Initial lodging: July 1 1 day-July 20th (10 day); Midnight: July 2 1 day-August 9 (20 days); Terminal: August 10-August 19 (10)

2, three volts, is the collective name of the first volt, the middle volt and the last volt, and it is the hottest season of the year. The dog days appear in the Gregorian calendar from mid-July to mid-August every year, and its climatic characteristics are high temperature, low air pressure, high humidity and low wind speed. "Fu" means that Yin qi is forced to hide underground by Yang qi. Three volts can be divided into initial, intermediate and final volts, and its date is determined by the coordination of the solar terms date of the dry branch calendar and the date of the dry branch calendar.

According to the traditional calculation method in China, the third and fourth Geng days after the summer solstice are the starting dates of the first (head) and the middle, respectively, and the first Geng day after beginning of autumn is the first day of the last. Because the interval between each Geng day is 10 days, the stipulated time for initial and final lodging is 10 days. And because the third Geng day (first fall) after the summer solstice solar terms appears sooner or later, the number of days in the fall is long or short, which may be 10 or 20 days.