The Last Man, supposedly given to our "editor" as cryptic, prophetic fragments written on Sibylline leaves, takes place in an imagined twenty-first century. This places it in a tradition of futuristic fiction that includes eighteenth-century works by authors such as Grainville and Mercier, for example, and, in the nineteenth century, Jules Verne and H. G. Wells. (On that tradition, see Paul Alkon.)
In the twentieth century futuristic utopias and--more often--dystopias have proliferated: from Gilman, Orwell, Huxley, Zamyatin, Pynchon, Chute, and Burgess, to (more recently) William Gibson, Neal Stephenson, and Octavia Butler, as well as numerous television shows, films, and computer games.
(It is also possible to speculate about the significance of particular dates in the novel, set three hundred years in the future from the French Revolutionary period.)
Romantic Circles / Electronic Editions / The Last Man / Note: the future setting