The third g-day after the summer solstice.
Three ambush days, one ambush is ten days, this is according to the number of tens of the heavenly stem to calculate. Therefore, the division of the three ambush days is: the third g day of the heavenly stem after the summer solstice is the beginning day of the first ambush. For example, the summer solstice in 2006, is the western calendar year of June 21, the day of the day of the heavenly stem day is Xin day, 28 days later, is the third day of the Geng day, so, July 20, 2006, is the beginning of the first voltaic; ten days later, another Geng day, that is, July 30, into the second voltaic; ten days later, another Geng day, and is the first Geng day after the beginning of the autumn, that is, August 9, into the third voltaic Day, it entered the third volt; if it is 2007, July 15 is the third geng day, is the beginning of the first volt (the first volt); ten days later, another geng day, that is, July 25, it entered the second volt (in the volt); ten days later, another geng day, but not yet over the Autumn, and then after ten days (this year's middle volt will have 20 days), another geng day, and is the first after the Autumn Geng day, that is, August 14, then entered the third volt. That is to say, every year into the three ambrosia days, are very hot, especially in the middle of the ambrosia of ten days (sometimes twenty days), is the hottest. There is a saying that "cold in the third nine, hot in the middle of the ambush".
New algorithm for the 21st century - Geng Day formula: GR = (D - [Y/4]) MOD10 (GR Geng Day, D even year 1 odd year 6, Y year, [] rounding, MOD take the remainder)
The first volts of GR plus 10 (2084 exceptions do not add), in the volts of GR +20, the end of the volts GR Greater than 7 times minus 1 less than 8 times plus 9 (2096 exceptions minus 1), for example, 2006 GR = (1-[6/4])MOD10 = 0 (10), the first ambush July 20, the middle ambush 30, the last ambush August 9.
How many days are there generally in the three ambushes?
The word "g" in geng day is the 7th of the 10 heavenly stems "A, B, C, D, E, F, G, C, N, D", and g is repeated every 10 days. Starting from the summer solstice, according to the arrangement of the dry calendar, the third geng day for the first ambush, the fourth geng day for the middle ambush, the first geng day after the fall for the last ambush. When the summer solstice and the fall between the appearance of 4 geng day in the ambush for 10 days, the appearance of 5 geng day for 20 days. It seems that the early or late appearance of the geng day will affect the length of the middle ambush, so there are some years 30 days of ambush and some years 40 days of ambush.
Three ambrosia days appear in the summer and summer, is the highest temperature in the year and humid, hot days. The so-called "Fu Tian'er" refers to the lunar calendar "three days", that is, the hottest period of the year. Can be understood in this way: "Fu" is the weather is too hot, appropriate ambush should not move. But the reason why the three ambrosia days are called "ambrosia" is because there are also many cold factors. Three volts is the hottest in the Central Plains in the year, 30, 40 days, three volts is calculated according to the lunar calendar, about in the solar calendar in late July to mid-late August.
Why is it so hot?
After entering the ambush, the humidity of the ground becomes greater, more heat is absorbed every day, less heat is emitted, and the heat of the surface layer accumulates, so it is hotter every day, and when it enters into the three ambushes, the accumulated heat on the ground reaches its peak, and the weather is the hottest. In addition, summer rain, air humidity, water heat capacity than dry air is much larger, which is also an important reason for the hot and stuffy weather. July and August subtropical high pressure to strengthen, under the control of the sub-high, high pressure within the sinking airflow, so that the weather is clear and less cloudy, conducive to sunlight, ground radiation warming, the weather is hotter.