The thing about science fiction stories is that in most cases the actual year they're set in isn't massively important. Sure if someone's going back in time to mess with historical events then it matters a great deal what date it is, but for a lot of stories something like 'the present day more or less', 'the day after tomorrow' or 'the 25th century' is enough. You don't really need to know what arbitrary year's been assigned to a movie; it adds nothing to your enjoyment or understanding to know that Alien takes place in 2122 or that 2001 takes place in 2001.
But I still want to know regardless, so I can stick them on a giant chart and go 'wow, Final Fantasy: The Spirits Within takes place after Demolition Man but before Starship Troopers!' So here's the dates I've pulled off the internet for some of the things I've written about on the site so far. I'm skipping Doctor Who though, you're on your own with that one.