How did trains standardize time in the United States?

Standard time is the synchronization of clocks within a geographical area or region to a single time standard 

During the 19th century, scheduled trains required time standardization in the industrialized world. 

Standard time was not enacted into US law until the 1918 Standard Time Act established standard time in time zones; the law also instituted daylight saving time (DST). 

This lesson explains some details of the history of time standardization in the United States.

https://ed.ted.com/lessons/how-did-trains-standardize-time-in-the-united-states-william-heuisler 

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