“Time,” the American science fiction writer Ray Cummings once observed, “is what keeps everything from happening at once.” The downside, of course, is that it also has a nasty habit of doling out birthdays with ever more implausible candle-to-cake ratios. Worse still, younger generations appear to genuinely consider things you clearly remember happening to be somehow historical events. Time, in other words, bends very much according to one’s perspective.