To say that something happens at night is to say that it happens during the nighttime. This usually means that it happens when it's dark outside.
The event happened at night, which is why it was so dark.
It's nighttime in America, which means that it's time for bed.
noun
the time after sunset and before sunrise while it is dark outside
Synonyms:
1
After the rankings or the nighttime chores, the Family goes to bed.
2
As well as for nighttime stands.
3
Causes of nighttime incontinence.
4
Daytime and nighttime benzos are not the same.
5
It was nighttime and very, very hot.
6
C. as a nighttime minimum temperature.
7
A big nighttime tiger, that's me.
8
The nighttime show was the syndicated Delilah.
9
This is the last day of nighttime celebration.
10
She then moved on to nighttime roles in the 1960s.