To fully understand time zones, a little history, a smidge of geography, and a touch of geo-politics all come into play. Let’s start with some basic geography and astronomy. The local time at any point on Earth is defined in relation to the local noon at that location. The sun rises, travels across the sky until it reaches its highest point in the sky, and then descends until it drops below your horizon. That highest point in the sky is called the “zenith” and it defines local noon.
Local noon at a given point on Earth varies from day to day as the length of the day varies. This was never an issue for local people as their day would start at sunrise and end at sundown – whenever that occurred. But as people began to settle in towns and cities, time became more important to accurately measure. Thus, the centralized town clock was invented.
Everyone remembers that iconic scene in Back to the Future when Marty and Doc use the lightning strike to transport the teen back to 1985. Marty arrives in 1955 carrying a flier pleading with Hill Valley residents to “Save the Clock Tower.” Have you ever wondered why Hill Valley, a fictional town in California, has a town clock to begin with? Sure, it was placed there by the screenwriter to move the story along – a timekeeping mcguffin. But why? Clock towers used to serve a critical purpose for towns around the world. In the days before time zones, every town functioned according to local time.
A town clock, often built in a public square, would serve as the official town time. People would set their clocks and watches to that time and adjust their personal timekeeping devices accordingly. Enterprising townspeople would offer their services as mobile clock setters, going door to door with their watch set to the town clock, changing citizens house clocks. The world ran just fine this way until the railroad was invented in the 1800’s.
The railroad allowed for the movement of people, livestock, and products quickly over great distance. Initially railroad schedules were incredibly confusing as trains moved between dozens of local time zones as it traversed the countryside. This led to all sorts of confusion. As the 19th century progressed, railroad professionals launched into discussions on how to mitigate the confusion, missed trains, and late arrivals.
In the late 19th century, Canadian Sir Sanford Fleming proposed the concept of time zones. Here’s where the geography comes in. Fleming recommended that the world be divided into twenty-four distinct time zones, each spaced 15 degrees of longitude apart. Since the earth rotates once every 24 hours and there are 360 degrees of longitude, each hour the earth rotates one-twenty-fourth of a circle or 15 degrees of longitude. Sir Fleming’s time zones were heralded as a brilliant solution to a chaotic problem worldwide. Different countries slowly began the use of time zones for railroad commerce. The US adopted the concept on November 18, 1883.
So now we have 24-one hour time zones. But where is the start of the day? In 1884 an International Prime Meridian Conference was held in Washington D.C. to standardize time and select the prime meridian (the place where the day would “begin”). The conference selected the longitude of Greenwich, England as zero degrees longitude and established the 24 time zones based on the prime meridian. The time at Greenwich England became known as “Greenwich Meridian Time.” This remained the standard time for decades until scientists looking for a more accurate counting of time, invented Universal Time Coordinated, or UTC, to communicate. Over the ensuing decades, countries began standardizing their times to comply with the Internationally recognized time zones.
All countries now comply to time zones, but not all time zones are the same. Some countries, like the United States, adhere to the 4 standard one-hour times zones across the lower 48 states. You either live in the Pacific, Mountain, Central, or Eastern time zone. But within those 4 zones, there are a few oddities. Arizona is on Pacific Time in the summer but Mountain time in the winter. This is because in the US there is “Daylight Savings” times. Each March time zones across the country artificially shift one hour later to allow for later sunlight hours in the evening. In October the time shifts back to standard time, allowing for sunrise to occur sometime before 8am across the country. Except in Arizona, Hawaii, Puerto Rico, and a handful of Pacific Island territories. The result is when you travel to Phoenix from LA in February you loose an hour. But in the summer, that same trip incurs no time change.
To further confuse the Arizona time zone confusion, the extreme northeast corner of the state is on Mountain time. Why? Because that area is largely part of the Navajo Nation. The Navajo Nation extends through the four corners, the other 3 states being New Mexico, Utah, and Colorado. All of them are on Mountain Time so to ease commerce and travel through the Navajo Nation, this portion of Arizona remains on Mountain Time all year as well.
The US isn’t the only country with oddities in time zones. Take China. China’s geographical expanse reaches across 5 time zones. However, the entire country operates on 1 time zone linked to the local time zone in Beijing. The same was true during the era of the Soviet Union. All 10 time zones were set to Moscow Time. Some countries like Australia, use half hour time zones as do several middle eastern and south Asian countries. Then there’s the trouble at the poles.
If you look at a globe, you’ll notice that as you travel from the Equator toward either pole, those longitude lines collapse toward each other. There are still 360 degrees of longitudes at the North and South Pole, but those lines converge, making the distance tiny. Thus, all researchers working at both poles use UTC.
The International Dateline poses its own oddities. The dateline was drawn at the 1884 International Prime Meridian Conference. It extends through the Pacific Ocean at roughly 180 degrees east longitude, or half-way around the planet from the Greenwich Meridian. The date line serves as a line of demarcation between 2 consecutive days. When you fly from the US to Australia, you “lose a day.” In other words, you take off on Friday night and land Sunday morning. Saturday never existed. But don’t fear! When you fly back home, you land in Los Angeles before you take off from Sydney! At least according to the local time in each location.
The date line isn’t a straight line. It zigs and zags to take into account different countries and territories that happen to straddle that region. Furthermore, despite its very formal name, the “International” date line has no legal international status. Countries are free to choose which date they wish to observe.
So the next time you find yourself 30 years in the future, stranded by a broken down Delorian, thank those smart townspeople from centuries back for creating the town clock. Without it, you’d likely be permanently stuck…in the future.