Every alarm, boarding pass and calendar invite on your phone depends on a text file that holds every clock rule a government has ever announced. A UCLA lecturer named Paul Eggert keeps that file current in his spare time, and at least four billion Android phones and iPhones read it. He is an open source maintainer, and he is far from the only one in that position. The xkcd comic that gets posted after every security scare, number 2347, shows a tower of modern infrastructure balanced on one small...