Why is life on Mars set in 1973?

Answer 1

Although no specific reason is known for 1973, the general time period of the early 70s was chosen for a number of reasons. The creators of the show, according to interviews on the DVD extra features, wanted to do a cop show since those were so popular. They realized that all the cop shows that they really liked were from when they were kids, such as The Sweeney, which first aired in 1975. Another influence on Life on Mars was the movie Get Carter, which came out in 1971.

These gave the approximate setting for the show. It is also possible that 1973 specifically was chosen because it was the year that David Bowie's song "Life on Mars?" was released as a single and made it quite high on the sales charts.