Sidley Park, Derbyshire, England, 1809-1812 and 1989 ("the present day")
All the visible action of the play takes place in the same room in an English country house, a couple of centuries apart. Keeping the action all in the same place underscores the similarities between the two plots, and the two eras in which they take place. While in the present day, Valentine waxes rhapsodic about what the information revolution has done for science, the rumble of Mr. Noakes's steam engine signals another revolution that ultimately made iPhones and Guitar Hero possible: the Industrial Revolution. By focusing on two moments of technological change through the lens of a single room that doesn't change all that much, the play suggests that the more things change, the more they stay the same.
Note #1: the play's stage directions say "the present day" rather than a specific year, but elsewhere (not in the play itself) "the present day" has been defined as 1989, which is four years before the play originally opened.
Note #2: For more on the pastoral setting of Sidley Park, see "The Garden" in "Symbolism, Imagery, Allegory."