From the date of the summer solstice to the third "Geng Day", you will enter the initial lodging, that is, the first day of lodging. In 222, the third "Geng Day" counted from the summer solstice is July 16th, which means that this day is the time of falling.

As the saying goes, "Three Geng's head falls in the summer solstice", which means that after the summer solstice, the third Geng Day is the day to start counting volts, and Geng Day is the ancestor. In ancient times, the heavenly stems and earthly branches Chronology Law was formulated, which made the ten-day trunk and the twelve places branch two two combination and sixty Jiazi in a cycle, that is to say, there is a Geng Day every 1 days, namely, Geng Wu, Geng Yin, Geng Chen, Geng Zi and Geng Zi.

Calculation method

Take 222 as an example. From the summer solstice, the first "Gengxu Day" is June 26th. The second "Geng Day (Geng Shen Day)" is July 6; The third "Geng Day (Geng Wu Day)" is July 16, so July 16 became the beginning day of this year's first fall (also called Toufu). The duration of the initial lodging is fixed at 1 days, so this year's initial lodging is from July 16th to July 25th. Fufu (also called Sanfu) is the first "Geng Day" after beginning of autumn.