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Hi,

In the following blank, we should fill in At or On, and what is the difference?

Chinese people celebrate the Moon Festival. ______ ( At or On) that night, families will get together, eat moon cakes, tell stories,.........

Thank you for the help.
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ON that night. 'At night' is idiomatic; if there is a modifier, 'at' no longer appertains.
Comments  

if there is a modifier
A premodifier or postmodifier? Now can we say something like this?:

-At the night (not THAT in this case) named he anchored his boat at the wharf.