When did the Mid-Autumn Festival first appear?

What originally did not exist but now exists—a dharma that appears later—is dependent origination (paratantra), a dharma born of causes and conditions. When the causes and conditions cease, when that upon which it depends changes or disappears, the dharma likewise changes and disappears.

When worldly people give rise to greed and grasping toward dharmas that arise in dependence on others, this is the imputed nature (parikalpita-svabhāva). That which can accord with causes and conditions to perfectly bring about dharmas that arise in dependence, as well as that which forms and manifests both the dependent nature and the imputed nature—this is the consummate nature (pariniṣpanna). Observe your own imputed nature: how foolish and deluded it is! All worldly habits are formed in this way. Dharmas that arise in dependence are so illusory and unreal, yet one insists on grasping at them, then forms habits, and finally they become deeply rooted in the mind, unbreakable. From this arise the delusion, karma, and suffering of birth and death.

Here is a contemplative practice (vipaśyanā-caryā) assignment for everyone: observe your own and others' grasping at the Mid-Autumn Festival, and contemplate the illusory and deluded nature produced by the imputed nature, as well as the illusory unreality of dharmas that arise in dependence. If you often contemplate in this way, you will be able to see through many meaningless worldly matters, and also see through the illusory unreality of the habits formed by sentient beings, and see through the arising, ceasing, and mutability of all dharmas, thereby reducing greed and grasping.

The Mid-Autumn Festival, a human convention that went from nonexistence to existence, is also grasped at as something inherent and made into a custom through attachment—all of this is nothing but putting shackles on oneself.