Of course it would be impossible to sell iPods in 1847 because there was no electricity, no computers, no software.
However, if the same weirdo from the future , this insane salesman selling a claim that you can listen to music on a metal cigarette box with glass in it, came knocking on your door trying to sell you an iPod in in 1900 – no luck, 1920 – no luck, 1980 - no luck. In 2000 – maybe.
This makes the point, albeit in an exaggerated and fanciful way, that to pursue luck you need to be persistent. At the original time you pitch your idea, your product or your service the world might not be ready for it. So keep going back, keep pitching, keep batting and one day the world just might be ready for what it is that you are offering.