Our sense of time begins with natural rhythms such as sunrise and sunset, which give us our conception of the day as a unit of time. It is common to think of a day as beginning with dawn, although Jewish tradition places the start of a new day at sunset, because Genesis tells us that first there was darkness, then God made light, and that was the first day.
Dusk and dawn are variable, though, unless you are exactly on the equator, so they are not the most objective way to keep track of time. High noon, on the other hand, is pretty much the same from solstice to solstice.
The idea of subdividing the day into hours goes back to antiquity. Days being measured from dawn or dusk, hour varied in the length of time assigned to them as much as the length of days themselves varied. In some instances, days were not subdivided equally into hours of equal length. Instead, hours were simply different significant points during the day, markers of when different activities were to commence, as in the canonical hours of the church, marked by the ringing of bells.
During the 13th century, the mechanical clock was invented in the monasteries of Europe, as a way of automating the ringing of bells to mark the canonical hours. The technology, which is the first form of automatic machinery, quickly spread to the cities. Lewis Mumford argues that this is the beginning of a mechanical revolution that leads to the invention of the printing press with movable type by Johann Gutenberg, and culminates in the industrial revolution.
The invention of the steam engine is generally considered to be the start of the industrial revolution. It was the result of technological evolution, the key figure being James Watt, whose work on this new source of power dates back to circa 1760.
The use of the steam engine as a source of power for railway transport, in the form of the steam locomotive, dates back to 1804, and sparked a revolution in transportation. An extensive railroad network helped to bind together the United States as a nation, with trains transporting more people and material, at faster speeds, than ever was possible before. (Harold Innis wrote about the significance of the railroad for Canada, and the same can be said of the smaller European countries.)
It was hard enough to build one set of tracks connecting various points all over the country, it would have been doubly hard to build two sets of parallel tracks for trains coming and going. And in truth, all that's necessary is to have some splits here and there, at least in theory.
The thing is, as railroad traffic increased, so did the number of train collisions, and catastrophes. The problem was that train schedules could not be coordinated when every city and town had their own time. Assuming that they all set their clocks to high noon, the one invariable point of the day, each place's time would vary along with the locality's relative position along the east-west axis. Variations of a few minutes would be enough to lead to an accident.
Coordination of local time keeping was not possible until the invention of the telegraph, by Samuel Morse in 1844. This first form of electric communications allowed information to be transmitted faster than a speeding locomotive, faster than any form of transportation, essentially instantaneously. The signal could then be send out to different places at the same time, synchronizing clocks and establishing a homogeneous region of time. Railway companies first established their own time zones in the mid-19th century, and then governments stepped in, ultimately resulting in the 24 time zones that the planet is subdivided into (much like a 24-hour clock).
The telegraph, the first form of wired communications technology, was followed by the wireless telegraph, which led to radio, and the further evolution of broadcasting into television.
And now this:
That clip came my way courtesy of one of my MySpace friends, MySpace being a product of the internet. The electronic media, television, satellites, and the internet have transformed the world, as Marshall McLuhan put it, into a global village. Therefore, looking towards the future, I think the time will come when there will be one standard global time (I wrote about this in an essay first published over a decade ago in Communication and Cyberspace), and that in turn will eliminate the need for regional time zones, opening up the possibility of a return to local time.