When the Club Kids are walking through New York at Night you can see the distinctive "green x" logo of Microsoft's X-Box games console in an advertisement. The film is set in the 1980's and the X-Box did not appear till the 2000's.
Much of the music that plays in the club scenes was not around when the original parties took place. For example, during the party where James St. James is in the "do not feed the drug child" cage (supposedly in the 80s), the music in the background is "Frank Sinatra" by Miss Kittin and the Hacker, a song which wasn't released until 2000. It is probable that the filmmakers knew about this, but used the songs anyway, due to their "retro" feel.