Hanshi day, the 4th day of the 4th lunar month, is the very day just before Pure and Bright Day. According to a legend, the day is in memory of Jie Zhitui who lived in the Spring and Autumn period.
Jie was a good official in the Jin state, who worked for chong er (Wengong). When the Jin state was in turmoil, chong er was forced to leave for other states. Jie took great pains to follow chong er. He even cut his own flesh on his leg and boiled for hungry chong er. After chong er got the monarch, he began to ignore and forget Jie by and by. Jie was so sad that he went home and lived in seclusion with his mother in mountains.
One day Wengong found Jie, a good official who sacrificed his flesh, was not around him and felt so guilty that he in person went to the mountains to look for Jie. But in endless trees and hills he failed to find Jie. He thought, since Jie was very pious to his mother, once the mountains were set on fire, he would come out with his mother on his back. So he ordered to set the mountains on fire. At last, the fire lasted more than 3 days, but Jie didn't show up. He and his mother were found to be dead in arms after the fire was put out.
This event made people respect and commemorate Jie. After that, people like to worship him on his death day, which was just before Pure and Bright Day. Because Jie was burned to death and people were not willing to cook food on that day and would rather eat cold food, that day is called Hanshi Day.