There's an xkcd (sorry, but I promise it's relevant) that graphs something similar to this[0] but using 'number of years from the time the story was written' as the second axis. If you look at it you can see a line indicating 'stories set in 2015' at the top of the graph - it would be interesting to plot a series of these isochronology lines and compare the stories that lie on them, although for SF you probably need more detail at the top right...