(How do we know it's 1980? Well, for one thing Peppermint Patty gets herself those Bo-Derek-in-10 cornrows -- Peanuts' timelessness occasionally shows a crack )
That said, The Complete Peanuts 1979-1980 includes a number of classic storylines, including the month-long sequence in which an ill Charlie Brown is hospitalized (including a particularly spooky moment when he wonders if he's died and nobody's told him yet),...