Question 1 out of a series of 5 similar questions that are found under the other boards.

Most people say 1964 because that's when the Vietnam War escalated, The civil rights movement, and the beatles!

1960 and 1969 are so different in so many ways.
At start the start of the 60's, there was always tension between Russisa and USA. Kennedy was President.
He was killed in 1963, his brother and Martin Luther King were killed in 1968.
The Music in 1960 differs greatly from 1969.

The answer depends of what you think defined the 60's. I think it's too hard to answer such a question.
Havins said that , there wasn't much of a change until Nov 63, when Kennedy died and 2 months later the Beatles were on Ed Sullivan. So there were 2 "60's". The one before and the one after the Beatles

1963 looks to be a good starting point overall, particularly the second half of the year. In addition to JFK getting shot, Black Rights was in full swing with the March on Washington and I Have A Dream Speech. The Beatles were also breaking through in Europe, and Motown was starting to get its own sound.  The Beach Boys also were becoming popular with songs like Surfer Girl and Surfin' USA. Even Elvis, huge c. 1960, was starting to fade with B-movies. But 1964 was the first 100% '60s year. I see two main '60s overall: the British Invasion/Motown (1963-66) era and the Psychedelic (1967-70) era. 1960- early 1963 was sort of the "Diet '50s", where stuff was still in the '50s world, but more modern overall and '50s slang/fashions, big from 1955-1958, were somewhat different. I'd say sometime during August 1963 was when the '60s culture finally eclipsed all '50s things; JFK had a newborn who died after just two days that month; a prelude to the big tragedy.