The first season of Happy Days takes place in 1955. The term "beatnik" did not exist until it was derisively coined by the newspaper reporter Herb Caen in 1958 riffing off the launch of Sputnik 1 the previous year.
The first season of Happy Days is supposed to take place in 1955-56, but, in the dialogue, Ralph says he has read Jack Kerouac's On the Road, a book yet unpublished by this circa (released in 57).