Cold Food Festival
The Cold Food Festival or Hanshi Festival is a traditional Chinese holiday celebrated for one day before Tomb-Sweeping Day. On that day, making fire is taboo and only cold food is available.
Legend has it that Prince Chong'er of the state of Jin during the Spring and Autumn period, endured many hardships while he was exiled from his home state. Once, in order to help the prince who was tormented by hunger, Jie Zhitui cut off the flesh from his thigh and offered it to the prince for sustenance.
When Chong'er became Duke Wen of Jin, however, he did not reward him, instead killing Jie and his mother in a fire. Later, Duke Wen, filled with remorse, ordered that using fire on the anniversary of Jie's death was forbidden and all food was to be consumed cold.
Source: China Daily