Prior to the advent of the railroad system, the keeping of time was a less than rigid endeavor. Clocks across regions (and even towns) would often vary significantly from each other with very few people concerned about the whole affair of imprecise time keeping. Very few people, that is, besides the men tasked with keeping the railroad running smoothly. When you’re in charge of ensuring two hundred-thousand pound locomotives don’t occupy the same space at the same time, those slipped minutes become a matter of grave importance.
The railroad-driven standardization of time keeping began in Britain in 1847 when all railroad clocks were synched to Greenwich Mean Time. By 1855 the majority of public clocks, regardless of their affiliation with the railroad, were also in sync. Standardization in the the United States took quite a bit longer as each major railroad company had their own standards. It wasn’t until 1883 that the heads of all the major railroad companies got together and agreed to use one standard to increase safety and efficiency. In 1918 the standardization of time was written into law in the U.S. with the passage of the 1918 Standard Time Act.