Why Do We Have Time Zones?

Why Do We Have Time Zones?

An Elementary Science Lesson

You probably have heard of time zones, but do you know why we have them? To better understand this question, it helps to remember a few key concepts from elementary school science class.

We of course live on the Earth, and the Earth spins on an axis. Every 24 hours, the Earth makes a complete rotation, and we call this a day.

The Sun shines light on the Earth. As Earth spins, some parts of the Earth receive sunlight, while others are dark. This gives us night and day.

From your location on Earth, you see the Sun rise when Earth rotates into sunlight. When you rotate out of sunlight, you see the Sun set.

Imagine if we had only one time zone on Earth. At noon, it might be nice and sunny where you live. But in another part of the world, it would be completely dark at the exact same time. These differences are at the heart of why we have time zones.

Before clocks were invented, people kept time using various methods. Among the earliest measuring devices were sundials, which told time based of the Sun’s position in the sky.

Cities and towns throughout the world would eventually establish their own local times, and this system worked for a while. Prior to the 19th century, people didn’t tend to travel that far. And for those that did, long travel times and lack of long-distance communication made time differences barely noticeable.

However, use of local solar time became more and more impractical as railways and telecommunications improved.

The Need for Time Zones

In 1830, the first passenger railway was opened at Liverpool Road in Manchester, England. Trains would run according to the sundial at each station where they arrived.  However, as you can probably surmise, this made it very difficult to keep the train running on time, and to know what time it would depart and arrive. It didn’t take long for railway companies to start campaigning for a single universal time zone to be used across the country. In 1847, a universal time was set in Greenwich, London, and was adopted as Greenwich Mean Time across the country.

Across the pond, the United States was having almost identical issues. American railroads maintained many different time zones during the 1800s. Pretty much every city used a different time, so there eventually came to be more than 300 local solar times to choose from. Railroad managers would eventually establish 100 railroad time zones, but this only put a bandaid over the issue.

Finally, in 1883, US and Canadian railroads instituted standard time in time zones. Standard time is the synchronization of clocks within a geographical region to a single time standard, rather than using local solar time. However, the new standard time system was not universally embraced.

Getting the World to Reset Their Clocks

Continued developments in transport and communication would further connect the world. Eventually, the benefits of time zones became apparent.

Britain would begin to gather international support for global time zones in 1884, led in part by Sir Sandford Fleming, a Scottish Canadian engineer who helped organize the International Meridian Conference.

The International Meridian Conference was held in Washington D.C., in October, 1884. At the conference, a proposal was adopted that set a prime meridian for longitude and timekeeping. It was decided that this prime meridian should pass through the Greenwich Observatory, in part because people had already informally recognized the Greenwich Meridian as the prime meridian even before the conference.

Greenwich Mean Time (GMT) was established as the world’s time standard. All time zones in the world refer back to GMT on the prime meridian.

Why Do We Have Time Zones?

Ultimately, time zones grew out of necessity, though their adoption would come gradually throughout the rest of the world.

In France, for example, Paris was considered the prime meridian until 1911. Time zones were not established in United States law until the Standard Time Act of 1918. The act also established daylight saving time in the nation. By the 1920s, many countries throughout the world would start using time zones. In 1972, Coordinated Universal Time (UTC) replaced GMT as the world’s time standard, and we continue to use time zones to this day.

So now, the next time to you travel abroad and have to reset your watch, you’ll at least know why.