After exams
The crunch time at the end of an academic year, when all fun or otherwise entertaining activities have to be postponed until all exams have been taken.
A: "Dude, you want to go hang out later this week?"

B: "Sorry, can't. Let's do that after exams."

C: "You totally have to check this out, it's like the coolest thing ever!"

D: "I don't have time. Ask me again after exams."