Forgive the more general nature of this post, but we have a wide demographic here and I thought I'd post something for fun. A friend and I have a theory that decades are not always 10 years long, and don't always happen from say 1960 to 1970. Various decades can different starting and ending points for things like music, politics, fashion, movies and cars. I have a few examples of what I think are starting and ending points, or icons of a decade in various fields. Feel free to correct me or add your own.
Politics
The 50's began with the election of Eisenhower in 1952 and ended with Kennedy's election in 1960.
The 60's ended with Nixon's resignation in 1974.
The 70's ended with Reagan's election in 1980.
The 80's ended with the Republican takeover of congress in 1994.
The 90's ended September 11, 2001.
Music
The 50's began with Bill Haley's "Rock Around The Clock" in 1954 and ended when the Beatles appeared on Ed Sullivan February 9, 1964.
The 60's ended the summer of 1969 with the dual events of Woodstock and the recording of Abbey Road.
The 70's began January 12, 1969 with the release of "Led Zeppelin".
Fashion
The 50's it's the poodle skirt for women and the leather jacket and jeans (ala Brando) for men.
Characterized in the 70's by the leisure suit.
The 80's by punk and Michael Jackson's zipper covered jacket.

