As Guy is arriving in Jakarta Billy Kwan's VO tells us it is June 25th, 1965, but the copy of Time Magazine Guy is clutching as he passes through immigration is actually the July 30th, 1965 issue with the famous Marc Chagall self portrait cover.
Note the the black Chevrolet, with left hand drive. Indonesians have generally operated right hand drive, and American cars were widely available in many parts of the world with right hand drive, in that era. Some USA manufacturers e.g. Ford Motor Company, GM, Chrysler did manufacture right hand drive automobiles in Canada for export to left hand traffic nations usually those from the British Commonwealth - in some cases some nations. e.g. Australia, South Africa, Thailand did assemble North American-market automobiles in their respective markets (especially with local content manufacture) where import tariffs are imposed.
In the sudden storm scene, when Guy and Jillian get into his car to get out of the rain. In the close reverse shot of Guy, water is clearly leaking heavily into the car through a crack in the door or window. But in the shot from behind the front seat of both the characters, there is no leak.
When Guy runs toward Jill as she is leaving the party to keep her from going to Billy, his left hand is covered with blood. When he returns to Billy and puts his hand under Billy's head, there is no blood on his hand.
The song by Richard Strauss is incorrectly listed in the end credits. It's "Beim Schlafengehen" ("Going to Sleep"), not "September." "September" is another of the "Four Last Songs" from which this one is taken; lyrics to both are by Herman Hesse.