Is there anything special about the first, eighth and ninth day of the seventh lunar month?

Because July 30th (February 29th of the lunar calendar) is the birthday of Bodhisattva, the King of Earth Treasure.

July 30th is the Christmas day and the birthday of the Earth Treasure King Bodhisattva.

In the old custom, July 30th is the "Birthday of the Earth Treasure King". On this night, incense is lit, ceramic tiles are placed on the ground in the shape of lights, and ointment, incense crumbs and so on are put inside. Streets and alleys are everywhere, and it looks like daytime when lit.

When people say "the earth hides incense", they worship the king of the earth. Another said that "burning incense in 1994" was to burn incense for Zhang Shicheng at the end of Yuan Dynasty.

Zhang was originally the leader of the peasant uprising, known as the King of Wu in Suzhou, and was later destroyed by Zhu Yuanzhang. His nickname is Jiu Si, and his birthday is July 20th. He burned incense that day and called it "Jiu Si incense". Later, he was mistaken for "salvation incense" and even called "shit incense".

In the past, on this day, people took their babies to the temple to send their names and asked for the blessing of the Buddha to make them "sons of the Buddha". Children wear new shoes every day. This custom has been abandoned for a long time.

Extended data:

The story of the Tibetan King and Bodhisattva:

Before the infinite robbery, the Tibetan King Bodhisattva was once a filial daughter named Guangyi. The naked woman's mother liked to eat fish eggs before her death and did a lot of killing business. Knowing that her mother would degenerate into an evil person after her death, the woman with light eyes invited arhat to sit down and watch and saw that her mother really suffered in hell. The light-eyed woman devotes herself to the Buddha and sincerely supports the Buddha statue.

Later, his mother was born to a woman with bright eyes. She was the son of a handmaiden. Less than three days after she was born, she was told that she was saved by a bright eye and reborn as an inferior creature. /kloc-at the age of 0/3, she will die young and suffer again because of killing and destroying her two jobs.

So Guangmu vowed to save all suffering beings in the future, and Guangmu's mother finally had to give up her bitter reward.

Baidu Encyclopedia-Birthday of Earth Hidden King