2015 is the year that Marty McFly arrives in a future of hoverboards, self-drying jackets and pizzas that come as tiny dried tablets.
Robert Zemeckis is a clever chap. When writing the Back to the Future movies, he chose the years 1955, 1985 and 2015. This is not just on the off chance.
A thirty year gap does of course play right for the intergenerational conundrums which befall the hapless McFly family, but thirty years is important for a more important reason. To sell movies (and boy, did that franchise sell), the writer needs to tap into something in an audience – a familiarity, a connection, an emotion. Setting the first movie in 1985 and 1955 is so easy because, effectively, they are the same year.