To lie in ambush means to enter the dog days. "Summer solstice, three Geng's head falls", which is the basis for establishing the first fall. The almanac stipulates that "the number of volts will be counted on the third day of the summer solstice", which means that "counting backwards from the summer solstice" and counting to the third "Geng day" will begin to fall. The "Geng Day" here refers to the day with the prefix "Geng" in the ancient "Ganzhi Jiri Law".

20 19 Summer Solstice Time: 20 19 June 2 1 day.

The first Geng Day after the summer solstice in 20 19: June 22nd, 20 19 (Geng Yin Day).

The second Geng Day after the summer solstice in 20 19: July 2, 20 19 (Geng Zi Day)

The third Geng day after the summer solstice in 20 19: July 20 19 12 (Geng Xu day)

Therefore, the first day of 20 19 was July 20 19 12 (Geng Xu Day). Because the initial lodging is 10 days, the initial lodging in 20 19 years is July 12-July 2 1 day.