Bud Brewster wrote:
In the year 2177 AD...
The Overlook Film Encyclopedia asserts that the action takes place in 2117, while the American Film Institute Catalog claims 2177. Anyone who watches the movie will encounter neither of those dates, but rather 2427 A.D. (as per the narration at 2:06).

One thing that Overlook and AFI do both get right, though, is the year of release for this movie, which is 1969. It premiered in Detroit, Michigan, on October 1st, 1969, and played across great swathes of the nation during November and December of that year. The 1970 date at IMDb is based purely on its belated opening in New York City. Furthermore, the National Screen Service code in the lower-right-hand corner of posters, lobby cards and 8x10s is '69/338', with the first two digits always referring to the year.

All of which may initially seem like nitpicking... but really, the entire mindset behind this film is very much end-of-decade, a kind of wondering-what-will-remain-of-the-Swinging-Sixties as a new future/decade looms. Whereas much of the softcore sexploitation produced in 1970  is marked by a more celebratory stance and concerned with 'seizing new opportunities' rather than expressing angst related to the end of an era.