What is medium? What is medium?

1, which starts from summer to the fourth Geng day in the future and ends on the day before the first Geng day after the beginning of autumn, is the second volt of the three volts, usually 10 day, and some years are 20 days. The so-called "three-volt fever" can be divided into initial, middle and final three volts, and its date is determined by the date of the solar term and the date of the branch year.

2. According to the traditional calculation method in China, the third and fourth Geng days from summer to the future are the first (head) and middle start dates respectively, and the first Geng day after beginning of autumn is the last first day. Because every Geng day is 10 days apart, the stipulated time of the first day and the last day is 10 days. Because the third Geng day (the first autumn) after the summer solstice solar term appears sooner or later, the number of days in autumn is long or short, which may be 10 or 20 days.