Set in the 1950s.
2 works chose this decade. They did not choose it from the same distance, so applying each gap from 2026 scatters them across 4 years — 1992 to 1996.
Back to the Future
Robert Zemeckis's 1985 comedy sent its teenage hero 30 years into the past, to a 1955 his parents remembered as their own youth. The film's arithmetic was never about 1955 in particular. It was about the distance between a teenager and their parents' adolescence — a gap that keeps moving.
Back to the Future Part II
The return to 1955
The sequel's future was 26 years out: a 2015 of hoverboards, self-drying jackets and a Cubs pennant. That date has been and gone, and the film is now marked against a scoreboard it never asked for — which is what happens to any future set close enough to check.