approved the festival in the region around Taiyuan. The Northern Wei similarly banned the festival in 478 and 496, but were also compelled to approve its observance around . These prohibitions failed to such an extent that, by the time of Jia Sixie's Qimin Yaoshu, a day-long Cold Food Festival had spread across most of China, moved to the day before the Qingming solar term. The Cold Food Festival grew to a three-day period and began to incorporate ancestral veneration under the Tang and remained more important than celebrations of the Qingming solar term as late as the Song. The present Tomb-Sweeping Festival on Qingming grew by incorporating the Cold Food observances along with the separate holiday of Shangsi. The Cold Food Festival had almost completely disappeared by the end of the Qing. Controversy Since the early 7th century, Chinese and Western scholars have argued for alternative origins for the festival. Du Gongzhan, the editor of the late-Sui Record of the Seasons of Jingchu, connected it with a ritual avoidance of fire mentioned in the Rites of Zhou: "In mid-spring, they announce the prohibition of fire in the capital using a bell with a wooden clapper". This prohibition was related to the ancient Chinese use of different kinds of firewood according to the seasons, particularly after the development of Chinese astrology that considered the heliacal rising of Antares to be an occasion for great risk of conflagration and wildfire. Du was followed in his conjecture by others, including Li Fu. The Sinologist J.J.M. de Groot argued for its origin as a celebration of the sun's "victory" at the vernal equinox, based on a comparative anthropological analysis drawing on Ovid, Macrobius, Lucian, and Epiphanius of Salamis. James Frazer and his followers similarly considered it either a "sun-charm" or "purification" from its similarities to other "fire-festivals". Claude Lévi-Strauss based his analysis of the festival as a kind of Chinese Lent upon a mistranslation of the relevant passage in the Rites of Zhou by Frazer. Eberhard connected it with his idea of a prehistoric spring-based calendar and made the Cold Food Festival a remnant of its original New Year. The unanimous connection of the festival to Jie Zhitui in the early sources and the dependence of these later theories on the Cold Food Festival's occurrence in late spring—when it in fact began as a mid-winter observance—suggests that none of them are likely accurate.