Negative Curfew
A set time at which an individual must not leave a social event before.

Used when someone is known to often go home very early at organised social events.

Usually secured by some kind of agreement involving a penalty if broken.
“Why’s Gareth still at this party, he’s usually got a lift home from Liam by 8pm hasn’t he?”

“Nah bro, he’s got a negative curfew with the group chat. Otherwise he’ll be in bed by 8:30 and he’ll regret it in the morning.”