The Cool Food Festival is the oldest and most important commemorative festival in China, with a history of over 2,600 years. In the Western Han and Eastern Han dynasties, only the people in Taiyuan celebrated this festival. In the Jin (265-420) and Southern and Northern Dynasties, the people throughout the country celebrated this festival. In the Tang Dynasty, it became a legal festival. At the festival, people ate cool food, walked on green grasses, offered sacrifices to the ancestral tombs, planted willow twigs, played football, on a swing or push-and-pull, wrote poems, appreciated flowers and held other activities. All the people in the country participated in these activities, ranking from the imperial family members to the people from all walks of life.