It doesn’t say when it is set. But, the story was published in 1961 and given the context and atmosphere of the story, and the A & P, it’s safe to say the story is set in the 1950s or early 1960s. The setting is a town north of Boston. But I can see how it could be generally interpreted as any suburban town in 1950s America.
You might say that conformity is as prominent today as it was then. You might be right. But these days, conformity is overtly challenged. In the 1950s, conformity and conservative social values were advocated more blatantly. This is in stark contrast to the revolutionary decade that would follow. This was the height of that idealized American Dream, complete with a nuclear family and a white picket fence around a suburban house. Speaking of conformity, suburban housing plans were designed with similar housing units. To some extent, this is still true today.
This was a place of architectural and social conformity. Certainly, the 1960s were the most revolutionary decade for America in the last 60 years. And in terms of industry and buying the latest material goods, it’s hard to say which decade showed the most conformity.
But in terms of social values, from 1950 to the present, the decade of the 1950s were the most socially conservative and conformist. This makes Sammy’s individual decision to leave his job more dramatic and significant. And he did so in camaraderie with the girls who were dressed very inappropriately by 1950 standards. If Sammy were to leave a job in 2011, it wouldn’t have the same existential or rebellious significance today than it would back then.