memorizing year of case is absolutely not needed! even preciese names of cases are not a must to know to gain your marks.
What you need to know is “ratio decidendi” of each case. And that is which situation, issue in law this case illustrates and what was the solution of it. You will need to those when you deal with scenerio based questions. Cases will serve to strenghten your arguments towards the decision that you take.
When you don’t remember part of case name u can say : case about … xx when you don’t remember case name at all you can say : “in a decided case”.