Constitution's B'Day yesterday, Time Zones today. A celebratory few days...
From The Library of Congress:
Time!An idea whose (cough) time (cough) had come. Cool tip -- cell phones are synchronized to NIST atomic clocks so if you want to know exactly what time it is (to the nearest second or three), check your phone. GPS receivers have better resolution but you need to hack them to get the time data out...
On November 18, 1883, four standard time zones for the continental U.S.A. were introduced at the instigation of the railroads. At noon on this day the U.S. Naval Observatory changed its telegraphic signals to correspond to the change. Until the invention of the railway, it took such a long time to get from one place to another that local "sun time" could be used. When traveling to the east or to the west, a person would have to change his or her watch by one minute every twelve miles.
When people began traveling by train, sometimes hundreds of miles in a day, the calculation of time became a serious problem. Operators of the new railroad lines realized that a new time plan was needed in order to offer a uniform train schedule for departures and arrivals.
Since every city was using a different time standard, there were over 300 local sun times to choose from. The railroad managers tried to address the problem by establishing 100 railroad time zones, but this was only a partial solution to the problem.
The fact remained that the different railroad lines were using time schedules that varied from each other and from the cities they passed through, causing considerable befuddlement. Where railroad lines using different time zones intersected with each other, or with cities using different time standards, travelers were especially confused.
During the mid-nineteenth century, people throughout the world had experimented with methods of standardizing their clocks. In 1830 the U.S. Naval Observatory was created to cooperate with Great Britain's Greenwich Observatory to determine time based on astronomical observations. Accurate sea navigation based on the calculation of latitude and longitude, depended on accurate timekeeping.
Samuel Morse's invention of the telegraph made it possible to coordinate time signals over long distances. In the 1840s, the Royal Greenwich Observatory established an official standard time for all of England, Scotland, and Wales. The U.S. Naval Observatory was responsible for keeping official time in the United States.
