For eons, all manner of animals have lived their lives according to the cycles of the Earth’s rotation on its axis, the moon’s orbit around the Earth, and the Earth’s orbit around the sun. But why do we observe the week? The pattern of living on a seven-day cycle—with one or two of those days set aside for rest—is a relative novelty. Only in the past few centuries, with Western colonization of most of the world, have the majority of human societies adopted it.

The case for the week was never airtight. It’s now weak and getting weaker. Most Westerners no longer observe a weekly Sabbath, and the coordination advantages of keeping everyone on the same uniform schedule have evaporated. So why does this arbitrary time cycle still dictate the rhythm of our lives? Is it time to abolish the week and find a better way to structure time?

The rationale for the day is as clear as, well, day. In a 24-hour period, most points on Earth experience a full cycle of light and darkness. It makes sense that humans and other organisms have evolved to adjust their patterns of behavior according to those daily patterns of light and heat.

Many organisms have also adapted to the annual environmental changes wrought by the Earth’s orbit around the sun. Countless animals migrate, hibernate, or breed on a yearly schedule. Humans have likewise long organized their lives around the annual fluctuations we call seasons.

The environmental influence of the lunar cycle is subtler, but no less real. It affects the tides and the amount of light available at night. While many animals have adapted their biology to the phases of the moon, it remains controversial whether humans have done so. (Despite its name, for example, we still don’t know for sure whether the female menstrual cycle evolved to be in sync with the lunar cycle).

But whence the week? Throughout history, human societies have found it useful to divide time into groups of days shorter than a lunar month. One of the most common uses of this cycle has been to establish a regular market day, though just how regular varies. At one point, the Basques evidently employed a three-day week. For centuries, China, Japan, and Korea employed a 10-day week. Other societies have employed four-, five-, six-, eight-, and nine-day weeks.

So how did lucky No. 7 come to rule our calendars? It all began logically enough, when the ancient Babylonians divided their lunar months into four, yielding weeks that were mostly seven days. Then superstition kicked in. The final day of the week came to be considered evil or unlucky, and certain taboos developed around that day—against eating meat, for example.

It’s likely that the Babylonian week was the model for the seven-day Jewish week, with its own taboos against certain behaviors on the seventh day, or Sabbath. Babylon also probably served as the source of another important seven-day week used in Hellenistic Alexandria. The influence of that week remains with us in the names of heavenly bodies it assigned to each day—like Saturn-day, Sun-day, and Moon-day.

Meanwhile, the Romans marked time differently, which is why you never heard of anyone warning Caesar to “beware the third Tuesday in March!” Roman lunar months began on the Kalends, which scholars believe coincided with the new moon. The Ides, which fell on the 13th or 15th day of a month, coincided with the full moon. The Romans also kept an eight-day market week.

As Christianity—which kept the Jewish week but moved the Sabbath to Sunday—and Egyptian astrology gained influence in the empire, so did the seven-day week. Constantine, the first Christian emperor, made it official in 321. Since then, the spread of Christianity’s influence—as well as that of Islam, which also employs a seven-day week—has imposed the seven-day cycle on most of the world.

But there’s nothing inevitable about the ceaseless repetition of six days of work, one day of rest. As labor has become both more productive and more organized, the week has evolved. The writer Witold Rybczynski traces the emergence of the weekend to 19th century England, when the British agricultural revolution made land and labor more productive. At first, Rybczynski relates, this allowed workers extra leisure, which they enjoyed spontaneously—not according to any ironclad schedule. As the Industrial Revolution became a driving force in trans-Atlantic civilization, the push for greater efficiency demanded standardization of this extra leisure. In 1926, Henry Ford began shutting his factories on Saturdays in a bid to crystallize an American convention of a two-day weekend full of recreation (that he hoped would involve driving). It worked.

Fast forward to 2014, and most of us in Western societies are still working or attending class five days a week, then taking a two-day break, then going at it for another five days, and so on. We’re as loath to spend Saturday at the office as we are unlikely to spend Tuesday at the beach. We go on living our lives in weeks, though the economic and spiritual logic for dividing time this way has grown outdated.

Yet the convention of the five-two cycle is already fraying at the edges. Congress has made a mockery of the workweek, as their 2014 legislative calendar illustrates. In media, the Internet and business pressure mean monthlies are now dailies, and dailies are now … minutelies? DVR has made weekly television viewing obsolete. And high-speed internet allows office workers to regularly “work from home” on weekdays, blurring the spatiotemporal lines between working and doing your laundry with the television on. But even when we cheat the week, we still acknowledge that it writes the rules. It’s time to stop letting it.

The mass standardization of the workweek, as a sort of compromise between labor and capital, was uniquely suited to the 20th century. The economic endeavors of that century were largely problems of large-scale coordination. Think, for example, of the difficulty of profitably moving Western cattle to Chicago slaughterhouses and unspoiled meat to East Coast butchers before the advent of cellphones, computers, and the interstate highway system. Standard business hours ensured that people within and across organizations were in place to perform their economic function at the same time (hence the standardization of timekeeping in roughly the same period). If the entire economy agreed to be open for business for the same five-day stretch, it solved a lot of coordination problems.

Today, advances in automation, computation, and telecommunications have routinized the large-scale coordination problems that challenged America’s 20th-century economy. The knowledge economy runs differently, and there is no longer such an overwhelming imperative for large numbers of people and goods to come together at the same place at the right times, or for those times to remain uniform across an entire society. Plummeting transportation costs and new forms of communication add to this greater flexibility. A software engineer in London can upload new code for, say, the operating system of a self-driving car at 4 a.m. on a Saturday. It will instantaneously be available to her colleagues in Boston and California whenever they need it, and their small team can easily arrange teleconferences on the fly as needed. Such activities benefit little from being organized on the weekly system.

Some may feel that the weekend is our one remaining buffer against work creep. But it isn’t! People already routinely work from home on Saturdays. Rather than a sacred refuge, Sundays are now both killing us and dying.

As for the spiritual logic for the seven-day week, I’ll abstain from making metaphysical claims, and stick to empirical ones. While some still keep the Sabbath by going to church, it’s clear Americans and Europeans no longer observe it religiously. Survey data has long showed that only about 40 percent of Americans report attending worship services weekly, and the actual level of attendance is more like half that because many respondents lie about how often they attend church. The numbers are lower in Europe: Only 3 percent of Danes, for example, reported weekly church attendance in 2004.

So how do we reinvent the week? While the 20th century saw innovation within the seven-day week, the 21st century ought to see innovation beyond the week. Yes, it’s been tried without success a couple times before (and I’m not just talking about that episode of Doug where Quailman invents Funday). The French Revolutionary Calendar divided months into three 10-day decades until Napoleon reverted to the Gregorian calendar in 1805. In an attempt to undermine religion and speed up industrialization, Joseph Stalin imposed five- and six-day weeks on Soviet Russia between 1929 and 1940. But in both instances, you had a central government and an atheist (or deist) elite trying to force a new week on a Christian majority as part of a total social upheaval. Where the iron will of Stalin failed, a free market solution could succeed.

The chief value of the seven-day week comes from the network effect: If you want to coordinate with other people, it’s useful to be on the same schedule as everyone else. Parents are unlikely to go off a five-two cycle as long as their children’s schools remain on it, and schools are unlikely to go off the cycle as long as parents remain on it. Just as in the Roman Empire, when a new week crept in from the margins, it will take groups insulated from the network effect and open to experimentation to come up with alternatives.

I can think of a couple contenders. There are Silicon Valley startups run by young people with few outside commitments and an obsessive focus on their venture. Lifehacking has already taken aim at daily sleep-and-wake cycles. Why not hack the calendar and find out whether there’s a most-efficient cycle of work and play? Of course, maximum efficiency isn’t life’s aim. Artist communities could also experiment with transcending the week. The year is like a blank slate, and each day a tile that can be arranged into a mosaic — whether in a regular pattern or some other way.

It’s hard to say what, if anything, should replace our seven-day cycle. Unlike the day, with its biological basis, there’s probably no universal need for weeks. In the end, a Silicon Valley week, a Brooklyn week, a school week, a Christian week, and maybe even Shark Week could happily coexist with no weeks at all, and people could attune their lives to the cycles that met their needs.