Posting this because I was binging through the seasons, as we all do, and this really popped out for me and I haven't seen anyone talk about it (maybe coz its a small detail) but

In S4E11 Basic Human Anatomy, when the Dean pull's Leonard's file to see his grades, he says "Back in 1968 Leonard got an A in Rotory Phone Maintenence, since then he has been taking every other class pass-fail"

In S4E13 Advanced Introduction to Finality, we see that Greendale was actually established in 1974.

Just thought y'all would want to know.