In other words, this concerns shows that doesn't use the present day for a setting while opting for a more retro or nostalgic kind of approach:
*Happy Days (1950s-1960s)

*Laverne & Shirley-The same time period as Happy Days since it was a spin off.

*The Wonder Years (late 1960s-1970s)-Even though I never thought of it as an actual sitcom.

*That 70s Show (you figure it out)

*That 80s Show (figure it out by yourself again)

*The Secret Diary of Desmond Pfiffer (Civil War era)

*The Flintstones (the Stone Age)

*Dinosaurs (same as the Flintstones)

*The Jetsons (a galaxy far, far away)

*Homeboys In Outerspace (same as the Jetsons)

*Hi Honey, I'm Home (1950s...sort of since it also took place in the present half of the time)

*Hogan's Heroes (World War II era)

Don't forget MASH, which took place during the Korean War. F-Troop which took place right after the Civil War. I'm not sure but I believe that McHale's Navy was also during either WWII or the Korean war.

Freaks and Geeks. It was set in the 70's.