Time Zones in the United States

In the early history of the United States, telling time was not always easy. Communities set their own clocks, using the Sun as their guide. This resulted in hundreds of regional times, and in some larger cities, clocks could vary between neighborhoods. Things got more complicated—and dangerous—with the advent of trains. Railroad lines often used different timetables, raising the possibility of collisions. To improve safety and efficiency, railroad companies adopted a standardized system of four...