When did the Cold Food Festival merge with Qingming Festival?

Cold food and Qingming merged in Tang Dynasty. Historically, cold food and Qingming are similar. According to "Tang Yao Hui Volume 82 Vacation", it is recorded: "(Kaiyuan) February 11th: The cold food has been cleared, and the fourth day is off. February 15th, 13th year of Dali: From now on, there will be a five-day holiday. To March 9, the sixth year of Zhenyuan: the cold food is clear, and it is appropriate to celebrate the Yuan Day, giving three days before and after. "

Therefore, "The Grand View of China Traditional Culture" contains: "Roughly in the Tang Dynasty, the Cold Food Festival and Tomb-Sweeping Day became one."

The Cold Food Festival was originally held from summer to 005 days in the future and one or two days before Tomb-Sweeping Day. When the first day of the day is a holiday, smoking is forbidden and only cold food is eaten. In the development of later generations, customs such as sweeping sacrifices, hiking, swinging, cuju, hooking hands and cockfighting were gradually increased. The Cold Food Festival lasted for more than two thousand years, and it was once called the largest folk festival in China. The Cold Food Festival is the only traditional festival named after the dietary customs of the Han nationality.