When was Qingming measured?

The traditional Tomb-Sweeping Day in China began in the Zhou Dynasty and has a history of more than 2,500 years. Tomb-Sweeping Day is first of all a very important solar term. As soon as Tomb-Sweeping Day arrives, the temperature rises, which is a good season for spring ploughing and planting. Therefore, there is a saying that "melons and beans are planted before and after Qingming". Agricultural proverb "Planting trees is not as clear as Qingming". Later, as the days of Qingming and cold food approached, cold food was the day when people banned fire to sweep graves. Gradually, cold food and Qingming became one, and cold food became another name of Qingming and became a custom of Qingming. On Qingming Day, there are no fireworks, only cold food.