What is an economy? You might say it is how people who cannot predict the future deal with it.  

People save money to protect themselves from calamity. Banks charge interest to account for risk. People trade stocks to bet on the earnings trajectory of a company. The first taxes were levied to support standing armies that could fight in the event of an invasion.

Time’s unknowable perils contributed to the flourishing of economic thought. But then something interesting happened. The creature became the creator: The economy re-invented time. Or, to put things less obliquely, the age of exploration and the industrial revolution completely changed the way people measure time, understand time, and feel and talk about time.

Just think: What do you look forward to when you’re at work? Maybe it’s a happy hour, the weekend, or, in the more distant future, retirement. Each of these are distinct periods of time, and each is an invention of the last 150 years of economic change.

The word weekend is a creation of the industrial revolution, since a discrete working week doesn't make much sense on a farm that needs constant tending. Retirement, as a term, dates back to the 1600s, as it relates to army service, but its modern usage only became mainstream after the move to an industrial economy. Happy hour is a neologism from the 1950s, a heyday for workplace optimism. The equally hopeful T.G.I.F. acronym comes from the post-World War II era.

Three forces contributed to the modern invention of time. First, the conquest of foreign territories across the ocean required precise navigation with accurate timepieces. Second, the invention of the railroad required the standardization of time across countries, replacing the local system of keeping time using shadows and sundials. Third, the industrial economy necessitated new labor laws, which changed the way people think about work.

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1. The Emperor’s New Clocks

The history of timepieces is a history of empires.

Long before the modern clock used springs and familiar markings, just about every great civilization had attempted to measure time, with each one failing in its own special way. In ancient Egypt, China, and Mesopotamia, sundials, or “shadow clocks,” all required bright sunlight to count the hours, which wasn't of much use on overcast days. To work around this problem, some of these ancient civilizations used a “water clock,” or clepsydra, a device that steadily dripped water through a small hole into a container with lines painted around the side to represent the passage of time. But slight changes in temperature could change the viscosity of water and the rate of drips. On a cold day, the water might freeze, and so would time.

The most important breakthroughs in the history of horology required the incentives and resources of a global empire. Toward the end of the Exploration Age, the great powers like England, France, and Spain struggled to navigate the oceans, because they couldn’t accurately measure longitude, or their progress east or west of their site of departure. As a result, they would crash into rocks or get lost and run out of food.

To some, this seemed like a problem of orientation. To John Harrison, an English carpenter, it was clearly a problem of time. Imagine that a ship departs from London for Jamaica with two clocks. The first clock keeps perfect London time throughout the journey. The second clock is reset to noon each day on the ocean when the sun reaches its highest point in the sky. As a result, the time difference between the two clocks grows as the ship sails toward the Americas.  As you know, the earth rotates 360 degrees every 24 hours. That means 15 degrees every hour. So, for each hour that the two clocks were apart, the ship had traveled 15 degrees west—or about 900 nautical miles, which is roughly the distance between New York City and Missouri; a time zone.

The scenario above isn’t a hypothetical; it’s precisely the calculation that Harrison made. The subject of the classic book Longitude by Dava Sobel, Harrison became famous for building the two most advanced clocks (technically: chronometers) of all time. His timepieces didn’t rely on the dripping of water, flow of sand, or even the swinging of heavy pendula. They were precise and durable enough to withstand the ricketty journey across the ocean. For his pains—he spent about 30 years designing and tweaking the timepieces—he won a luxurious prize from the British government.

The British Empire didn’t merely help perfect the modern timepiece but also helped to popularize the watch. In the late 1800s, watches were considered to be feminine jewelry; men kept their timepieces tucked away in pockets. But in colonial campaigns like the First Boer War and the Third Burmese War, British commanders tied little clocks to their soldiers’ wrists. Going into battle with feminine jewelry might have struck the men of war as uniform malfunction. But the innovation proved extremely useful for coordinating troop movements.

By World War I, watches were standard-issue gear for soldiers in the trenches. When the men who survived came home, they retained the habit. Thus the wristwatch, conceived as a piece of jewelry for women, was re-marketed through colonial warfare as a thoroughly masculine fashion. By the 1930s, wristwatches were the norm and the pocket watch was an anachronism. Time, itself, had become a human appendage.

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2. Time-Zone Travel

Time and space are connected, not only in the fabric of the universe, but also in our idioms. We talk about time as an interval applying both to moments (“It’s fifteen minutes to five”) and to geography (“I’m fifteen minutes from Five Guys”). Perhaps this is why the invention of a machine to zoom through space, the train, inspired the idea that a machine might travel through time.

The rise of the railroad in the 1800s startled the era’s scientists and inspired a new ecstatic language of progress. In 1864’s Journey to the Center of the Earth, Jules Verne imagined a machine that, rather than navigate the circumference of the earth, departed along the perpendicular axis to travel inward through the mantle of its sphere. In 1895’s The Time Machine, H.G. Wells’ protagonist embarks along another dimension, time, as if history itself were a navigable rail line stretching from past to future. Humans had been trying to predict the future since before the Oracle of Delphi. Only after the invention of trains did they imagine visiting it.

The discovery of machine-power was, in many ways, the discovery of the future. “Travelers riding in steam-driven railroad trains looked out their windows onto a landscape where oxen plowed the fields as they had done in medieval times, horses still hauled and harrowed, yet telegraph wires split the sky,” James Gleick writes in Time Travel, his wondrous interdisciplinary history of the subject. (Those interested in a simpler history of time might also enjoy the delightful young-adult book This Book Is About Time.) “This caused a new kind of confusion or dissociation,” Gleick wrote. “Call it temporal dissonance.”

Dissonance is right. The railroad created a crisis of time management unlike anything human beings had ever experienced. In the pre-train age, all time was local, divined mostly by the angle of the sun in the sky. If Philadelphia and Harrisburg had different times, nobody noticed, because a Philly resident couldn’t reach Harrisburg by phone or rail to tell the difference. As a result there were hundreds of local times in the United States.

Local time was perfectly suitable for a local agrarian economy. But for a railroad company and its customers, it was a nightmare. Imagine walking through an airport terminal (already logistical chaos) and learning that Delta and United now operate by entirely separate time schedules: A United flight that takes off, on-time, at 1pm leaves at the same time as a Delta flight departing on-time at 2pm, and the clocks on the wall correspond to neither Delta nor United.

That sounds ludicrous. But for the first railroad travelers, this scenario was commonplace. In Buffalo’s train station, each railroad company used its own time schedule. The New York Central Railroad ran on New York time. The Michigan Southern Railroad schedule ran on the local time of Columbus, Ohio. And both of those clocks were distinct from the clock that represented local Buffalo time.

As Gleick writes, “railroads made time zones inevitable.” The railroad companies finally got together in the 1880s and decided to divide the U.S. into four standard time zones: eastern, central, mountain, pacific. This required local communities to forfeit their control of time, which didn’t go over well in a country founded on federalist principles. To many, the standardization of time seemed like a national takeover. Others accused jewelers of orchestrating the time-zone revolution to make people buy new clocks and watches.

The four zones were set on November 18, 1883. The precise times were dictated by another new technology that seemed to pierce the boundary of space and time, the telegraph. The following year, the International Time Conference established the plan for global time zones, which included an International Date Line. And so, wristwatches and standard time—perhaps the two most famous icons of horology—were both children of travel.

Nobody complains much about time zones any more, unless they’re whining about jet lag. Instead, we reserve our hate for Daylight Saving Time (DST). Initially instituted by Germany to save fuel during World War I, DST was first proposed in the U.S. during the same war. Contrary to the popular idea that daylight saving time was a carrot to farmers, it was urban retailers looking to save artificial light costs who were among the staunchest advocates. Farmers actually led a national effort to repeal national daylight saving time in 1919. Year-long DST returned in 1942, when President Franklin D. Roosevelt instituted “War Time,” two months after Pearl Harbor, and only returned to normal standard time in 1945. Time waits for no man, but when a nation is at war, it gets pushed around quite a bit.

Beyond standard time, the subtler impact of railroads was their invention of the 21st-century concept of a career. The word itself comes from the French carriere, meaning a racetrack. To achieve its modern meaning, however, work required an element of vocational progress. Farm workers reached peak earnings as early as their 20s. But it took decades for railroad employees to earn their highest wages even in the late-1800s, as late as their 40s.

As the economy shifted from plows to rails, it changed the shape one’s lifetime earnings. Rather than a wage progression resembling a great plain—a flat, unchanging (or, perhaps, unpredictable) salary for many decades—the industrial revolution delivered the familiar curve of income that modern workers recognize, with gradually rising wages until middle-age followed by a slow decline. And so, the industrial economy invented the very concept of a modern career, making the passage of time a materially significant matter for turn-of-the-century workers. (In fact, even the term “turn of the century” was only invented at the dawn of the 20th; before that, presumably, the centuries faded, like the shadow of sundials, or ran dry, like water clocks.)

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3. Working for the Weekend

“What’s your schedule like?”

It is one of the most common questions imaginable in a modern workplace. But if you asked somebody in the 1400s or 1700s, she would have no idea what you were talking about. The English word schedule dates back to the middle ages, when for hundreds of years it merely signified a slip of paper. But the modern definition—an orderly sequence of events and times—is a far more recent invention, coming from the late 1800s. The word first applied to a railroad company’s list of train departures. (As does the word commute, derived from a “commutation ticket” or a season pass to a streetcar or railroad.)

For the next half century, American industrialists become obsessed with optimizing, well, schedules. If the late 19th century turned time into a cultural fascination, the 20th century turned it into an economic denominator.

The 1910s saw Henry Ford’s Model-T assembly line and Frederick Winslow Taylor’s The Principles of Scientific Management. Taylor’s productivity treatise divided labor into discrete activities—open the mail, hammer the nail—and encouraged maximizing production over time (while often minimizing wages over time). The first use of time clocks to mark workers’ hours of arrival grew in tandem with Taylor’s scientific management theories. Once a tool of military coordination, watches had become keepers of factory efficiency. Even their manufacturers advertised time-clocks as tools for a “profitable” employee.

As for the workers, the long history of the U.S. labor movement has been in many ways an attempt to move from an open-ended commitment to work as long as possible to a legal framework to limit the workday and workweek—a protest to reclaim time. Some of the first American labor protests called for a 10-hour work day, something today’s workers would consider horrific.

But they had to start somewhere, since it wasn’t uncommon for early-1800s textile employees to work 12 hours daily. In 1840, Martin Van Buren signed an executive order for a 10-hour day. By the 1860s, the Grand Eight Hours Leagues and the Knights of Labor were pushing to shave another two hours off the workweek. In 1868, President Ulysses S. Grant signed a proclamation instituting an eight-hour work day for government employees. It was extended to railroad workers in 1915 and then to the entire private sector under the Fair Labor Standards Act of 1937. Soon the labor movement’s attention turned from the workday to the workweek, advocating for a two-day weekend. Between 1920 and 1927 the number of large companies with official five-day workweeks increased by a factor of eight.

All told, in the last century and a half, the workweek has shrunk from 10 hours a day, six days a week, in the 1880s, to eight hours a day, five days a week—a 33 percent reduction. Where did the extra time go? Much went to leisure. The whole mountain of media that has grown in the last century—including weekly magazines, movies, radio, television, cable, and social media—relies on a resource, mass attention, that became abundant only as work declined as a share of the week.

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4. The House of Time

The quantum physicists say that past and future are illusions. They say time is more like space. It something that merely exists rather than unfolds. Imagine a house. All of the rooms are simply there, and it is an illusion that one room comes “after” or “before” another room. Instead, each individual’s consciousness passing through the house creates the illusion that there is an inviolable sequence of rooms.

The quantum theory of time would seem to have nothing to do with our economic history of horology. Some scientists say time doesn’t technically exist? you might think. Who cares, it sure as heck exists for me! Normal people experience time as a flow, an infinite cascade of falling dominos, a chain of cause-and-effect events that neither leaps forward several moments nor suddenly reverses, but rather passes with the predictable click-click-click of now moments falling into the next with a steady cadence.

The purpose of an economy is to manage the perils of the future, to make sense of time, to make it work for us. In the 1930s, the economist John Maynard Keynes predicted that future economic productivity would reduce the long workweek to just 15 hours. So it’s ironic that after several millennia of economic thought and evolution, some of the richest Americans haven’t used their wealth to buy downtime. They’ve used it to buy more work. The richest Americans now work longer hours than they did a few decades ago.

As I’ve written, rich American men, in particular, are the world’s chief workaholics, putting in longer hours than both rich people overseas and lower-income Americans. It’s hard to say why. Perhaps mobile phones are an unbreakable leash. Perhaps the hunt for status and wealth among the plutocracy is yet another tether. Or perhaps rich people just love working (“building wealth to them is a creative process, and the closest thing they have to fun,” as the economist Robert Frank wrote).

A recent study suggests that many of these workaholics have their values perfectly backward. Al E. Hershfield and Cassie Mogilner Holmes, assistant professors at the Anderson School of Management at UCLA, asked 4,000 Americans of various ages, income, jobs, and marital status: Would you take the money or the time? About two-thirds of their respondents said they’d take the money.

But those who valued time over money were happier, even when the researchers controlled for income. Among people with similarly high income, those most satisfied with life were far more likely to choose time. As they wrote, “the value individuals place on these resources relative to each other is predictive of happiness.”

So much of what we now call time is a collective myth, devised by emperors, industrialists, protesters, and tinkerers. It’s ironic, then, that the happiest workers are those who labor to buy time rather than money. The workaholics serve an illusive god. Then again, as the quantum physicists would say, so do we all.