Variations on the year it's set.

leading from: Prometheus - The Return of the Space Jockey

1. Ridley did not want to put an exact year on when the original Alien movie was set when he made it back in the 1970s, but imagined it generally taking place a hundred years in the future. In October29, 2009, he talked to Empire magazine about the upcoming alien movie "The prequel will be a while ago. It's very difficult to put a year on 'Alien,' but [for example] if 'Alien' was towards the end of this century, then the prequel story will take place thirty years prior."

2. The Mike Goodridge article in Screendaily.com 26 April, 2010 without quoting, says that the movie will be set in 2085. He heard Ridley Scott say:“If the first Alien took place in 2090, it will take place in the years before that when they first come across this thing on a planet called Zeta Reticuli and it will ask who was that guy in the first film lying in a chair with his chest blown outwards when they first go into the giant spacecraft.”(Mike Goodridge of Screendaily.com) (Read about the issues regarding saying that the planetoid is Zeta Reticuli or was in that star system )

3. However the problem with this is that in MTV interview, Ridley confirms that the sequel will be set in 2085, however states that the events of Alien prequel will take place thirty year before Sigourney, whether that is to say before Sigourney's character Ripley was born or before Ripley encountered the alien creature is another matter, but Ridley says that the prequel be set in a period before she was born