At the beginning of the movie, when the computer reawakens upper functions, the screen shows the location of the Nostromo. On the left side of the screen, this information is given-
Actual Time 3 Jun
Flight Time 5 Nov
(I believe in reality the years would be given. However, the creators of Alien may have wanted this information left out to give the film a flexible time period, sometime in the future.)
Amazingly, this is pretty accurate. As you go faster in velocity, the further you go into the future.
One other little note: the Nostromo has inertial dampners. This may be the first instance in a movie or episode where this concept is employed.
Oh, and Planet of the Apes did the ship time vs. objective time thing, too.
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"I ran into Charlie Fogg.
He blacked my eye, and he kicked my dog.
My dog turned to me, and he said,
'Let's head back to Tennessee, Jed.'"
-The Grateful Dead, "Tennessee Jed"
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"Gone savage for teenagers with automatic weapons and boundless love."
--
Soul Coughing
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"I ran into Charlie Fogg.
He blacked my eye, and he kicked my dog.
My dog turned to me, and he said,
'Let's head back to Tennessee, Jed.'"
-The Grateful Dead, "Tennessee Jed"
------------------
"Gone savage for teenagers with automatic weapons and boundless love."
--
Soul Coughing