Why? It’s called Time Zones. It’s the law in the United States and in most countries in the world. It’s the law because most countries want to have a standard number of hours for daylight, no matter where in the country you live. Let’s say you go to school at 8 a.m. Is the Sun up? More than likely. But when the Sun comes up before 8 a.m. in New York, kids who go to school in California would have to go to school in the dark if they had to go at the same time as you do. Why? Because the earth turns, that’s why. Each day, the earth completes one full turn. Parts of the earth are pointed toward the Sun for half of the day and then the other parts of the earth are pointed toward the Sun for the other half of the day. By making it 8 a.m. in California when it’s 11 a.m. in New York, California schools can have kids show up for school at 8 a.m. and also have sunlight to greet those schoolkids. The same is true of business and other parts of life.

We didn’t always have time zones, though. For thousands of years, people didn’t even keep track of time at all, at least not in the way that we know. Sundials, water clocks, and other time pieces marked the passage of the Sun across the sky, but nobody was talking about seconds, minutes, or hours way back then.

A few hundred years ago, clocks and watches were invented and timekeeping became a focus for many people. But nobody really had an idea yet that time zones were needed.

It wasn’t until 1878 that man named Sanford Fleming (who was born in Scotland but moved to Canada) proposed dividing the world into 24 time zones, each spaced a certain distance apart, according to measurements made on a globe. This arrangement was adopted by many countries. It divided the United States into four time zones: Eastern, Central, Mountain, and Pacific. Each time zone as you go west is one more hour behind. Central is one hour behind Eastern. Mountain is one hour behind Central and two hours behind Eastern. You already know that Pacific is three hours behind Eastern.

American railroad companies helped by using the time zones for their train schedules. The railroad had exploded across the American landscape by this time, and the train companies wanted their trains to run on time. An agreement between the major companies was put forth in 1883. The agreement established an official time as well. Central Time and Mountain Time might differ by an hour, but they differed by exactly an hour.

Finally, in 1918, Congress passed the Standard Time Act, which made the four time zones official. The Eastern, Central, Mountain, and Pacific time zones were now enforced by federal law. Clocks were also set to a certain time on the minute hand as well. Before, time varied from place to place depending on what time people thought it was.     

The map dividing the U.S. into the four time zones doesn’t always go straight down state lines. Some states, for instance, are in two different time zones. Florida, Indiana, Kentucky and Tennessee are part of both the Eastern and Central time zones. Kansas, Nebraska, North Dakota, South Dakota, and Texas are part of both the Central and Mountain time zones. And Idaho and Oregon are part of both the Mountain and Pacific time zones.

So, as you take a trip through Tennessee, you might see clocks that say two different times. It just depends on whether you’re in eastern or western Tennessee. Why is this the case? Well, for one thing, not all the states had become states yet when the railroad companies started using their time zones in 1883. Not even by 1918 were all the states in the Union yet. Hawaii, the last of the 50 states, became a state in 1959. (Hawaii and Alaska are entirely different matters because they’re so far to the west. Hawaii is three hours behind California; Alaska is one hour behind.)

What does all this mean? It means that the more you travel in the United States, the more you’ll need to check your watch!