1.1. About Time Zones - History

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• published: 12 Mar 2016
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- [Voiceover] In this chapter, we'll kick off our exploration of time zones with a quick look at the history of how time zones became what they are today. Legally, socially, and commercially, it's always been important to work from an agreed-upon time. If a law goes into effect at midnight, then we need to agree on when midnight takes place. If a friend wants to meet for coffee at 11:00, you wanna have the same time in mind so you don't miss each other. If a shop will be open from 9 a.m. to 5 p.m., then the customers need to be keeping the same time as the shop. Early on, sundials and apparent solar time were the best way to do that. Basically, look at the sky, see the sun, see how high it is in the sky, and try and decide what time of day it is. Over time, we began to use clocks, clock towers, and chimes in order to keep every city in a unified time. If you wanted to know when it was noon, well, the clock tower told you it was noon, and you probably heard the chimes letting you know. And you could set your watch accordingly. More complex concepts of time became necessary as humans made a series of transportation and telecommunication advances. In the 16 and 1700s, we had ships. In the 1800s railroads and telegraph. And in the 1900s, cars, planes, and telephones. Before 1600, it was enough to have a single city working from the same time. As it became easier to travel and to communicate, it became important for far-away places to be working with the same time. We take for granted now that when we pick up the telephone that the person on the other end will have a time that matches ours, even if they're in a different time zone. But that wasn't always the case. One major milestone in the path towards getting everyone synchronized on the same time was the invention of Greenwich Mean Time, or GMT, which was established in 1675 when the Royal Observatory was built in Greenwich Park, London, England. The Royal Observatory was created to assist ships in determining their longitude at sea. Greenwich became the prime meridian, or zero degrees longitude. And the time in Greenwich became an official time. GMT provided a standard reference time, which could then be used to calculate the local time in different ports and cities. Why Greenwich, England? It wasn't the only place attempting to create a meridian or a standard time. But Britain had more ships than the rest of the world put together, and the quality of the data from the Royal Observatory was excellent. That worked well until the age of railroads and telegraphs. Suddenly, it wasn't okay for each city to be keeping their own time. Instead, it became necessary to agree on a common standard time for large regions or entire countries. And so we get this idea of railway time, which is based on GMT. It was established in 1847. And most cities in Great Britain were using GMT by 1855. They were all in sync and using the same time. Now, it wasn't just important to have the same time in mind to know when your train was gonna arrive, and make sure you didn't miss it. Trains actually collided before railroads kept a common time. This was also a big problem in the United States, and it led to the United States adopting a common time as well. The United States is much larger than Great Britain, so they actually divided up the country into five different time zones. You can't simply have a single time zone across such a large area because the sun rises and sets at such different times depending on which side of the country you're in. Now, the United States had a common time, and it had time zones. But it wasn't based off of GMT. From 1850 to 1900, most countries began using a standard time because they realized that they needed it. But it was not based on GMT; it was based on a local observatory. Now, that's good enough for railroads and telegraphs across a single country, but as countries became more interconnected, then having strange offsets became a problem. For example, you could cross a border and then have to set your watch forward by 48 minutes or some other odd number. Even if you were traveling directly south, you might cross into a new country which kept a slightly different time. It was way too confusing. So from 1900 to 1929, most countries changed over to use a GMT synchronized time, and they had even hourly offsets from that. When you change to a new time zone, you would change in a simple increment, usually one hour. And, perhaps more importantly, countries within roughly the same longitude now all rounded to the same one hour number. It greatly simplified the system and gave birth to the idea of time zones. Time zones are geographic regions in which a single standard time is used. Now, there are roughly 24 time zones, one per hour of the day. And that means that each time zone is approximately 15 degrees of longitudinal width. That's because if you take 360 degrees and divide it by 24 hours, you come up with 15 degrees.