Albert Einstein wrote, “For us convinced physicists the distinction between past, present, and future is an illusion, although a persistent one.” Mathematically speaking, time can move forward or backward with equal ease and propriety. In our “real” world, however, time plunges ahead relentlessly, and practical men have invented a vast assortment of timekeepers, from sundials and hourglasses to the most precise atomic chronometers, to record time’s metronomic progress. But the more accurate they are as machines the less they accord with human experience, and human experience is the main ingredient of good films, which is why “temporal realism” is such a meaningless phrase.