1, “volt” means that the yin is forced by the yang to hide underground, there are three volts per year, and the three volt days are the hottest time of the year. 2, from the summer solstice, according to the arrangement of the stem and branch chronological days the third G day for the first volt. The fourth G day is the mid-volts. The first G day after the autumn is the last ambush. 3, the word “G” is “A, B, C, D, E, H, G, Xin, Non, Dec” the seventh word in the ten days of the stem, G day every ten days repeated. 4, the start and end of the voltaic days vary from year to year, roughly in the middle of July to mid-August. How is it calculated? China’s popular “stem and branch chronology” with the heavenly stems and earthly branches to match the 60 groups of different names to remember the day, every day with the word G is called G day. 5, the Qin and Han dynasties prevailed in the “five elements of mutual reinforcement”, that the hottest days of summer is fire, and G is gold, gold is afraid of fire melt (fire grams gold), so to G day, gold will hide. So from the summer solstice after the third G day for the first volt (10 days), from the summer solstice after the fourth G day for the volt (some years is 10 days, some years is 20 days), the first G day after the autumn for the last volt, also known as the final volt (there are 10 days), known as the three volts. 6, when the summer solstice and autumn between the appearance of four G day mid-volts for 10 days, there are five G day is 20 days, so the mid-volts to the final volt sometimes 10 days, sometimes 20 days, while the “first volt” and “last volt” are 10 days. 7, China’s lunar calendar “nine” is the customary use of miscellaneous sections, there are “winter 99” and “summer 99”. Among them, “winter nine nine” is widely spread, it is the winter solstice as the starting point, every nine days for a nine, nine nine each year a total of eighty-one days. The third and fourth nine days are the coldest time of the year. The “Summer Nine-Nine” starts with the summer solstice, and every nine days is a nine-nine, with nine nines for a total of eighty-one days each year. Similarly, the third and fourth nine days are the hottest seasons of the year. It contrasts sharply with the “Winter Nine-Nine”, which unfortunately is not widely circulated, but in fact the “Summer Nine-Nine” does vividly reflect the relationship between dates and weather.