Equinox trailer [YouTube]
On IMDb, the link to the trailer for this 1970 horror film takes you to a trailer for the 1992 Alan Rudolph film of the same name. Good as Rudolph is, his trailer is no match for this. Trivia: in the horror film the word "equinox" is spoken in the 1967 student-made original (it refers to a boundary between good and evil, living and dead) but is never uttered in the 1970 recut.
More on the 1970 Equinox here.