How did you know that day was the first boxer day?

You can look it up in the calendar. The day with the word "Geng" is called "Geng Day". The word "Geng" in Geng Day is the seventh word in "A, B, C, D, E, G, Xin, Ren, Gui" 10 day, and it is repeated every 10 day. Starting from the summer solstice, the third Geng day is the first Geng day, the fourth Geng day is in the middle, and the 1 th Geng day after beginning of autumn is the last Geng day.

origin

"The third watch" means that the three characters "Geng" appear in the summer solstice, and the third watch is the first time. "Youth Pai Qiong Lin" said: "The first dog days are the third night of the summer solstice. "Because the number of heavenly stems is 10, there is a Geng Day every 10 day, such as Geng Zi Day, Geng Yin Day and Chen Geng Day. 365 days a year (366 days in leap year) is not an integer multiple of 10. One day this year is Geng Day, and next year is not necessarily Geng Day. Due to the uncertainty of Geng day, the date of entering the cave is different every year.