1. The first lunar month of 2021 is from July 11th to 20th, which is 10 days.

2. The specific date of Sanfu is determined by the combination of the dates of the solar terms and the dates of the zodiac signs. The traditional calculation method in my country stipulates that the third Geng day after the summer solstice and the fourth Geng day are the starting dates of Chufu (Toufu) and Zhongfu (Two Fu) respectively, and the first Geng day after the beginning of autumn is the last day. The first day of summer.

3. The dog days of summer appear between the mild heat and the extreme heat. They are the hottest, humid and sultry days of the year. The reason for the high humidity in the Dog Days is that the southeast wind blows in the Dog Days, and the Pacific and Indian Oceans are in the southeast. The air is moist. The humidity of the wind causes the high humidity in the Dog Days. In late autumn or winter, on the contrary, the northwest wind blows, and the northwest is the dry inland, blowing the dry and cold wind to the mainland, so the humidity in winter is low.