(from The Migrant Times; the original story is here https://themigranttimes.org.nz/stories/2016/9/22/celebrations-mid-autumn-and-the-67th-anniversary-of-the-founding-of-china-celebrated?rq=mid-autumn)

History and traditions of the mid-autumn (moon-cake) festival

(source: ebeijing.gov.cn - the official website of the Beijing Government)

"One of the most important traditional Chinese festivals, the Mid-Autumn Festival falls on the 15th day of the eighth lunar month, around the time of the autumn equinox (usually September 22). As the full bright moon on that night tends to inspire people's anticipation for a family reunion, it is also called "Festival of Reunion."Moon cakes and watermelons (cut into the shape of a lotus) are indispensable for the Mid-Autumn Festival.

The festival is a traditional festivity for both the Han and minority nationalities, with a history of more than 2,000 years. The custom of worshipping the moon (called xi yue in Chinese) can be traced back to as far as the ancient Xia and Shang Dynasties (21-11th century BC).

In the Zhou Dynasty(11th century-256BC), people held ceremonies to greet winter and worship the moon whenever the mid-Autumn set in.

It became prevalent in the Tang Dynasty(618-907) for the people to enjoy and worship the full moon.

During the Southern Song Dynasty(1127-1279), however, people sent round cakes to their relatives as gifts to express their best wishes for a family reunion.

Nowadays, while many customs of playing under the moon are no longer observed, the custom of enjoying the bright silver moon and eating moon cakes remains an important part of the Mid-Autumn Festival."