The sweet green rice ball is a Qingming Festival (Tomb Sweeping Day) food popular in Jiangsu and Zhejiang Provinces. It is also a must-have offering at ancestral rituals in the south of the Yangtze River. The custom of making sweet green rice balls dates back to the Zhou Dynasty over 2,000 years ago. One or two days before the Qingming Festival were designated as "cold food days", during which hot cooking is banned.