When the group of men ascend the hill to get to the commune, it is daylight. When they reach the top of the hill, it is still broad daylight. Later, when Marge descends the hill, it is still daylight, but ends up being pitch black when she reaches the bottom.
In 1971, the U.S. military would have not paid to return old, obsolete helicopters and other junk seen on the deck of Ray's ship back to the U.S. It would have been given to South Vietnam or abandoned or scrapped in that country.
As Ray starts driving from Oakland to Los Angeles, he turns on the radio and a song starts to play. There is a fade edit to denote the passage of time, yet the song continues playing uninterrupted even though after the fade the car is passing Santa Clarita (about a five hour drive from Oakland).
The story takes place in 1971, but the whole-year calendar poster in Ray's cabin on the ship is for 1976 (same as 1971 after February 29th).
Although set in 1971, the ship Ray is working on, the S.S. Austral Glen, was not named that until 1975.
The story takes place in 1971 but the pinball machine in the bar Ray visits upon arriving in the Bay Area was created in 1974.