We Live By a Unit of Time That Doesn’t Make Sense

The seven-day week has survived for millennia, despite attempts to make it less chaotic.

An illustration of a weekly calendar, with each day represented by its first letter and the letters "WTF" highlighted in red
Felipe Estay Miller

Days, months, and years all make sense as units of time—they match up, at least roughly, with the revolutions of Earth, the moon, and the sun.

Weeks, however, are much weirder and clunkier. A duration of seven days doesn’t align with any natural cycles or fit cleanly into months or years. And though the week has been deeply significant to Jews, Christians, and Muslims for centuries, people in many parts of the world happily made do without it, or any other cycles of a similar length, until roughly 150 years ago.

Now the seven-day week is a global standard—and has come to dominate our sense of where we stand in the flow of time, according to David Henkin, a historian at UC Berkeley. His new book, The Week: A History of the Unnatural Rhythms That Made Us Who We Are, traces the evolution—and analyzes the curious staying power—of what he lovingly refers to as “a recalcitrant calendar unit.”

The week as we know it—a repeating cycle that has seven distinct days and divides work from rest—has been around for about 2,000 years, since ancient Roman times. The Roman week itself blended two separate precedents: One was the Jewish (and later, Christian) Sabbath, which occurred every seven days. The other was a rotation of seven days tracked by timekeepers in the Mediterranean; each day was associated with one of seven celestial bodies (the sun, the moon, and five planets).

The week has kept its shape since then, but Henkin argues that it has taken on new power in the past 200 years as it has become a tool for coordinating social and commercial plans with ever-widening circles of acquaintances and strangers. I recently spoke with Henkin about how the week shapes our perception of time and why it has survived, even in spite of efforts to tinker with it. An edited version of our conversation follows.

Joe Pinsker: The seven-day week has existed for a long time, but you argue that there was a fundamental shift during the 19th century in how it was perceived. What changed?

David Henkin: The week became far more important to people’s ordinary lives, beyond the question of whether it was Sunday, the day of rest, or not. It became what is in some ways the most stabilizing calendar unit that we have: When you think it’s a Tuesday and it turns out to be Wednesday, you feel disoriented in a way that you don’t typically if you think it’s the 26th and it turns out to be the 27th. That’s the change: the real grip on our time consciousness that the week exerts.

Pinsker: How and why did this happen?

Henkin: If you were to single out one factor, I would say urbanization. This really is a social phenomenon: It’s about people wanting to be able to make schedules with others, especially strangers, either in a consumer context or socially. When most people lived on farms or in small villages, they didn’t need to coordinate many activities with folks whom they didn’t see regularly.

It’s become much more important to know what day of the week it is. Today, a lot varies between one day of the week and the next—entertainment schedules, violin lessons, custody arrangements, or any of the millions of things that we attach to the seven-day cycle.

Pinsker: How did this change make time feel different?

Henkin: It’s hard for me to prove as a historian, but I do think that when we are more attuned to this cycle, because it’s shorter than a month, it feels like time moves much more quickly. When our Mondays are different from our Tuesdays and our Wednesdays, it does kind of feel like, all of a sudden, It’s Monday again?! You can see in 19th-century diary entries that, more and more often, people describe this feeling by referring to how another week has come and gone.

Pinsker: You write about efforts made 100 to 150 years ago to “reform” the yearly calendar and make weeks more orderly. What problems were those efforts targeting?

Henkin: The goal was to “tame” the week—to have it make more sense. The week is this bizarre unit of time—it’s the only one that doesn’t fit neatly into the fraction of any larger unit, like everything else does, from seconds to centuries. One issue is that, for businesses, it causes bookkeeping irregularities when you have a different number of weeks in a month, a quarter, or a year.

The reforms were also sold as solving a broader problem, which is that saying today is Tuesday, November 16, 2021, is technically a redundancy—there is no November 16, 2021, that isn’t also a Tuesday. And when people mix up weekdays and dates—say they mistakenly schedule something for Wednesday, November 16, which might not exist in a given year—it can cause all kinds of confusion.

Pinsker: What changes did the reformers want, then?

Henkin: Their solution was to change the calendar so that November 16 is always a Tuesday. The most popular calendar-reform proposal was for the year to consist of 364 days that always have the same weekday attached to them, and then to have a couple “blank days” at the end of the year that don’t count as part of any seven-day week.

Reforms like these were heavily supported by business interests in the United States, as well as the scientific community. This was the period when the international date line was established and when time zones were instituted. Reform movements were successful in getting governments to go along with Greenwich Mean Time. It just didn’t work with the week.

Pinsker: And why did this reform movement fail?

Henkin: The main answer is a religious answer, because no Christian, Muslim, or Jew who’s attached to the idea that you can count seven-day weeks all the way back to creation is going to think that you can just move it around. Also, I’m a practicing Jew, and it would really mess up my life if what I had to observe as Saturday or as Wednesday wasn’t what other people thought was Saturday or Wednesday.

But a lot of other people are attached to the weekly calendar for nonreligious reasons, despite knowing it’s not real. Once people got used to thinking of Tuesdays or Wednesdays as real things, it’s not surprising that they were hesitant to dispense with that notion.

Pinsker: Even though the week isn’t grounded in any naturally occurring cycles, it does feel like a weirdly perfect amount of time for spacing out certain recurring activities, like vacuuming or calling a family member. Do you think that there’s something about our natural rhythms that the week actually captures?

Henkin: I think that’s totally plausible. One hypothesis is the one you offered: The reason the week has survived is because it happens to be really well matched with things. My hesitation about that is that the things it’s well matched with seem so historically constructed—like, the question of how often you should talk to your mom wasn’t the same in eras before the telephone. One neurological explanation that’s been suggested is that the seven-day week originated—or, more plausibly, survived—because humans are good at memorizing things up to seven. So the seven-day week could just be a good cognitive fit.

And then there’s another hypothesis, which I’m a little more drawn to because I’m a historian: that our sense of what is an appropriate amount of time to wait between activities has been conditioned by the week.

Pinsker: In your book, you note that the 24/7, always-on nature of modern life has eroded some of the week’s shared rhythms, because the internet lets people set their own schedules for watching TV, shopping, or checking the news. Do you think the week is fading in importance?

Henkin: When I began this project, I had the sense that maybe I was documenting the modern experience of the week just as it was about to unravel. But by the end of it, I was less sure about the unraveling. I do think there’s been some attenuation of the week’s power. But on the other hand, writing this book made me feel like the week will likely survive. What happened earlier in the pandemic is a great example: People were disoriented because they didn’t know what day of the week it was, and that experience was a telling symbol of the unmooring of time.

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