When and how did the count of 93 volts start to be calculated?

The "number nine" is counted from the date of the "winter solstice" (February 2 1 or 22, Gregorian calendar 65438) every nine days. The dog days are the hottest time of the year, starting from summer to the fourth Geng Day in the future and the last Geng Day after beginning of autumn.

The number "Nine" in the lunar calendar is a miscellaneous festival used in China. When you enter the winter solstice, count to nine, which is what people call "Winter Count Nine". It starts from the winter solstice. Count nine days is 19, count nine days is 29 ... counting "99" is the end of "99". March 9 and April 9 are the coldest seasons of the year.

There are many customs of counting nine, and the custom of "drawing nine" has appeared since the Ming Dynasty. The so-called painting is actually a picture that calculates the warm date of spring after the winter solstice. In the Ming Dynasty, "A Brief Introduction to the Scenery of the Imperial Capital" contained: "From winter to the sun, draw a plum flower, one in eighty petals. Dye one petal a day, and 99 petals will come out, then the spring will be deep, saying that 99 will eliminate the cold. "

The word "Geng" on Geng Day is the seventh word in ten days of "A, B, C, D, E, Ji, Geng, Xin, Ren and Gui", and Geng Day is repeated every ten days. Dog days mean dog days, which are 30 to 40 days after the third Geng day from summer to the future. This is the hottest time of the year.