The "Mid-Autumn Festival" in the north is on July 15th, and in South China it is on July 14th.
It is generally believed that the Mid-Autumn Festival is also called the "Orchid Festival"; In fact, there is a great misunderstanding in this understanding. Correctly speaking, the ancestor worship festival on July 14th, the Mid-Autumn Festival and the Yulanben Festival belong to folk customs, Taoism and Buddhism, and they are in a side-by-side relationship, not three different names of a festival. Since the rise of Taoism, the word "Zhongyuan" in the "Sanyuanshuo" was officially fixed as the festival name in the middle and late Tang Dynasty, and the festival date was set on July 15th. This festival is a festival in which the three customs are integrated.
Before the formation of "Mid-Autumn Festival", July 15th had already been requisitioned by Buddhism. July in Buddhism was originally a happy month for a Buddha, not a "Ghost Festival". But why did the Bonin Festival in July become a "Ghost Festival"? Euglena basin, a transliteration of Sanskrit Ulambana, originally meant to "save the hanging upside down", that is, to save the ghosts suffering in hell.
The Buddhist scripture "The Orchid Sutra" was translated and introduced to China in the Western Jin Dynasty. The story of "saving the mother through a blind eye" in the sutra coincided with the concept of filial piety that still existed at that time. Later, it was advocated by Xiao Yan, Liang Wudi of the Southern Dynasty, who praised the theory of "three religions coming from the same source" and made it a folk festival. At that time, its main function was to worship the Buddha.
It was only in the Song Dynasty that it changed and developed into a ghost that recommended death. I don't know if it's a coincidence, or whether it's the Bonin Festival, the Mid-Yuan Festival and the Bonin Festival of Taoism attached to Buddhism, which are all set on July 15th. So that later generations thought that these two were two names of a festival. At the same time, because its meaning and customs have long been difficult to distinguish, the customs of the two festivals began to be mixed.