1915 to 1965 vs 1965 to 2015

[TheDeadFlagBlues]

The answer is almost certainly 1915 to 1965.

The widespread diffusion of radios, television sets and household appliances would have marveled any time-traveler. Along with this, and I think we take this for granted, the mass culture of the 1960s would have been pretty shocking to someone from 1915, who lived in a world where inward-looking cultural communities defined along class and/or ethnic boundaries were still dominant. Standards of living would have appeared near-utopian to any time-traveler, along with the provision of social goods. Then, there would have been the shock that comes with the realization that the Old World had been completely shattered by World War I and World War II. The end of empires, the total collapse of cultural paradigms and more would have really shocked a time-traveler. Not to mention the knowledge of genocide or atomic weapons or jets.

In social terms, not all that much has changed since 1965. The patterns that organize our day-to-day lives have remained the same, for the most part. Frankly, I think that any time-traveler from the 60s would be disappointed by 2015. In 1965, there was a pervasive sense of "progress" and our era could not, even if history went exceptionally well, live up to those expectations.

Computers are cool but they pale in comparison to washing machines or refrigerators or vacuums. I think we really take for granted how important these items are/were and the progress they stood for.

[TheDeadFlagBlues]

An important change which took place between 1965 and 2015 was the decline of the mass audience, which happened because of the Video Cassette Recorder, the cable TV, the Internet, the DVD set, Youtube, Netflix. There was  segmentation of the audience.
However, this is not more important than the rise of the mass audience which took place between 1915 and 1965.

One of my friends posted a snippy critique of this idea by saying: "the internet was supposed to kill mass culture yet I still google 'Star Wars' three times a week".

Memes are a great example of "mass culture" emanating from novel technologies; the same goes for "viral videos" or aggregator sites that promote mass culture. All in all, there has certainly been a decline in mass culture but it's still present. The converse is also true of the 50s or 60s: people are prone to over-stating the cultural homogeneity of both periods. There were expansive subcultures and distinct cultural differences between regions based on traditions of one kind or another.