Why is the thirteenth day of the first lunar month not good?

People think that the thirteenth day of the first month is an unlucky day, and there are even rumors that the thirteenth day of the first month is taboo even for dead faces.

According to folklore, Wang Yan has thirteen sons. By virtue of his status as a strict monarch of the underworld, he is in charge of birth, illness and death. He often said that even if a son dies a month, he will not die a year. When the Jade Emperor heard about it, he decided to punish the Yanjun. So since February, a son of Yan State has died every 28 days. On the 13th day of the first month of the following year, thirteen sons of Yan happened to die.

In fact, there are many kinds of sayings. The 13th day of the first month is the most taboo day for Yan. But I can't escape the framework of the above story after all, except that the protagonist in the story has changed from Yan to other characters. This legend actually comes from "Thirteen Taboos in Yang Gong", also known as "Taboos in Yang Gong". In the eyes of our ancestors, there are thirteen days of Pepsi every year. The thirteenth day of the first month is also among them.