This festival originated in a fairy tale. A hero names Hou Yi saved his people by shooting down the other nine suns that burned his people to death. He was then bestowed with the elixir of immortality by the Queen Mother of the West.
He did not want to consume the elixir and leave his beautiful but very mortal wife, Chang Er, so he gave the elixir to his wife for safekeeping. Unfortunately, Hou Yi’s disloyal apprentice forced Chang Er to swallow the elixir. She then became a supernatural being. She flew to the moon, and from there watched her husband.
Knowing that his wife had now been separated from him, Hou Yi was crazed with grief. Looking up at the moon one night, he saw a figure like his wife. He hurriedly took cakes and succade (preserves in sugar, whether fruits, vegetables, or confections) as offerings to his wife.
Upon hearing this, people developed the custom of watching the moon and eating moon cakes annually on this day.