January 13, February 11, March 9, April 7, May 5, June 3, July 1, July 29, August 27, September 25, October 23, November 21, December 19. Yang Gongji's day is the death day of Yang Gongji. Because Yang and Yang are homonymous, Yang Gongji's day is mistakenly written as Yang Gongji's day of death, which is also called "Yang Gong13's day of death". It is said that Yang Junsong, the geomantic master of the Tang Dynasty, set it down.
origin:
Once upon a time, there was an old man named Yang. The neighbors called him Yang Gong. Yang Gong has 13 sons who are both civil and martial, and are famous far and near. The Jade Emperor was jealous because he didn't have a son. On the 13th day of the first lunar month, the King of Hell told the old man that according to the "Book of Life and Death", the old man died a son every month, which was just over in a year. Yang Gong said that he has 13 sons. He has died one son every month for 12 months of the year, and there is still one left. How could he die? As a result, from that day on, the King of Hell asked Yang Gong to die a son every 28 days, and died separately within a year. These 13 days are the 13th day of the first lunar month, the 11th day of February, the 9th day of March, the 7th day of April, the 5th day of May, the 3rd day of June, the 1st day of July, the 29th day of July, the 27th day of August, the 25th day of September, the 23rd day of October, the 21st day of November, and the 19th day of December. Every time these days, Yang Gong will sacrifice his son, so later generations will call the 13th day of the first lunar month and related days "Yang Gong Sacrifice".