The twenty-to-thirty-year lag between reality and TV-land. Shows that first ran in The Nineties often reminisced The Seventies, shows in The Eighties carry a lot of cultural baggage from The Sixties, shows that first ran in The Seventies hearken back to The Fifties, and shows in The Fifties and The Sixties had its nostalgic setups between The Gay Nineties and The Roaring Twenties. At the start of the 21st century, this can be seen in how some works seem to suggest that they took place in The Eighties when they are supposed to be set in the present-day or a little earlier. In such settings, the "cool kids" still rap and skateboard and the lingo is still Totally Radical (even in cases where it was not relevant to begin with). In many cases, it's clear that someone Did Not Do the Research.