<P> The history of standard time in the United States began November 18, 1883, when United States and Canadian railroads instituted standard time in time zones . Before then, time of day was a local matter, and most cities and towns used some form of local solar time, maintained by some well - known clock (for example, on a church steeple or in a jeweler's window). The new standard time system was not immediately embraced by all . </P> <P> Use of standard time gradually increased because of its obvious practical advantages for communication and travel . Standard time in time zones was not established in U.S. law until the Standard Time Act of 1918 of March 19, 1918, also known as the Calder Act (15 USC 260). The act also established daylight saving time, itself a contentious idea . </P>

When did time zones start in the us