Curfew is at 11pm every night, but Jimmy will only stay up until 2am before passing out.
However this trophy is accumulative so if you stay out multiple nights after curfew then you will get this eventually, it will only take 2-3 nights at most.
You have to be outside your dorm for this to count as well, you cannot wait inside the boy's dorms.
You have to be seeing the message on your trouble meter "Violating Curfew" for this to be counting basically.