What exactly does "midsummer on the solstice will be summer" mean?

Also known as the "third Geng from summer solstice", it actually means that the third Geng day after the "summer solstice" solar term begins to decline. In other words, the third Geng Day after long summer every year is the first day of the dog days of the solstice.

Xia Fu, that is, three volts, is a general term for initial, intermediate and final volts. Early autumn begins on the third Geng day in the future, Mid-Autumn begins on the fourth Geng day after Liqiu, and late autumn begins on the first Geng day after Liqiu. According to the trunk and branch calendar, every 10 day is a Geng day. The initial and final fixation is 10 days, and the intermediate fixation may be 10 days or 20 days.

Take 20 18 as an example. From summer to the future, the first Geng Day is June 27th (Chen Geng Day), the second Geng Day is July 7th (Geng Yin Day), and the third Geng Day is July17th (Geng Zi Day). So the first day of "ambush" is July 18 (Boxer Day). Because the initial stay is 10 days, the initial stay on 20 18 is 17 from July to July 26th.