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Reading Passage 2 – Keeping the Same Time

A Before the nineteenth century, few people had any reason to know what time it was anywhere other than in their own town. Time was local: noon was the moment when the sun stood highest in the sky, and because the sun appears to travel from east to west, noon arrived a little later at every place further to the west. A town a hundred kilometres west of another would therefore keep time several minutes behind it. Public clocks on churches and town halls were set by sundials or by astronomical observation, and nobody was troubled by the fact that neighbouring towns disagreed.

B The railways changed this. When journeys that had once taken days could be completed in a few hours, differences of a few minutes began to matter. A passenger reading a timetable needed to know whether a departure time referred to the clock at the station he was leaving or at the one he was travelling to, and staff scheduling trains on a shared line needed a single reference if collisions were to be avoided. In Britain, individual railway companies began to run their trains according to London time, and within little more than a decade most of the country's railways had adopted it.

C This so-called railway time did not win immediate acceptance. Many towns continued to keep their own local time on public clocks, and some clocks were fitted with two minute hands, one showing local time and the other railway time. Critics complained that an arrangement designed for the convenience of commercial companies was being imposed on everyone else. Nevertheless, the practical advantages proved hard to resist, and over the following decades the great majority of public clocks came into line. Parliament finally made Greenwich Mean Time the legal time throughout Great Britain in 1880.

D In North America, the problem was far greater. The continent was so wide that a single national time was impossible, and before the 1880s the railroads operated on dozens of different times, often each company's own. On 18 November 1883, the railroads of the United States and Canada introduced a system of standard time zones, each covering a broad band of territory and differing from its neighbours by exactly one hour. In many places, the change took effect at midday, and the occasion became known as 'the day of two noons', because in towns that had to turn their clocks back, noon arrived twice. Remarkably, the new zones had no legal basis in the United States until 1918; for more than three decades, they were simply an agreement among private companies.

E Meanwhile, astronomers and geographers were debating a related question: from which line of longitude should the world measure east and west? Different nations used their own capitals or observatories as the starting point on their maps and charts, which caused confusion for navigators. In 1884, delegates from more than twenty countries met at a conference in Washington, D.C., and voted to adopt the meridian passing through Greenwich, in London, as the world's prime meridian. One reason for the choice was practical: a large majority of the world's shipping already used charts based on Greenwich. Not every country accepted the decision at once, however; France, for example, continued to use the Paris meridian for many years afterwards.

F The conference did not establish a worldwide system of time zones, but it prepared the ground for one. Over the following decades, country after country adopted a standard time defined in relation to Greenwich, most commonly a whole number of hours ahead of it or behind it, although a few chose offsets that include an extra half hour or even three-quarters of an hour. In practice, zone boundaries rarely follow lines of longitude exactly; they bend around national and regional borders, and some large countries have chosen to use a single time across their entire territory.

G Today, the precise time is no longer set by the sun, or even by an observatory at Greenwich. Since the 1960s, the second has been defined by the vibrations of atoms, and the world's official time scale, Coordinated Universal Time, is maintained by combining the readings of hundreds of atomic clocks in laboratories around the world. Yet the basic idea remains the one that the railways made necessary: people in widely separated places agreeing to read the same hour from their clocks. It is easy to forget how recent that agreement is, and how much argument it took to reach it.