Decimal time
Based on Wikipedia: Decimal time
The Revolution That Wanted to Kill the Hour
In the chaos of revolutionary France, as heads rolled and kings fell, a group of intellectuals decided that the real enemy of liberty was the number sixty.
Think about it. Why do we divide hours into sixty minutes, and minutes into sixty seconds? The answer reaches back four thousand years to ancient Babylon, where mathematicians fell in love with sixty because it divides evenly by so many numbers—two, three, four, five, six, ten, twelve, fifteen, twenty, and thirty. This made calculations easier in an age before calculators. But to French revolutionaries drunk on rationality and eager to sweep away every vestige of the old regime, this sexagesimal system (from the Latin word for sixty) was an irrational relic of superstition, as outdated as the monarchy itself.
So they killed it. Or tried to.
Ten Hours in a Day
On October 5th, 1793, the National Convention decreed that the day would henceforth contain exactly ten hours. Each of these decimal hours would contain one hundred decimal minutes. Each decimal minute would contain one hundred decimal seconds. Midnight became "ten hours." Noon became "five hours."
The math was intoxicating in its elegance. Under this system, if someone told you the time was 1 hour, 23 minutes, and 45 seconds—written as 1h23m45s—you could instantly convert this to 1.2345 decimal hours, or 123.45 decimal minutes, or 12,345 decimal seconds. No more wrestling with the conversions between sixty-based units. Three hours equaled precisely 300 minutes equaled precisely 30,000 seconds. Clean. Beautiful. Revolutionary.
There was just one problem: a decimal second lasted only 0.864 of our familiar seconds. A decimal hour stretched to 144 of our minutes—two hours and twenty-four minutes of lived experience crammed into the word "hour." The revolutionaries had created a system that made perfect sense on paper and almost no sense to actual human beings trying to meet for lunch.
The Watches That Counted to Ten
Watchmakers, ever eager for commissions, produced elaborate timepieces with dual faces: one showing traditional time with numbers climbing to twenty-four, another showing decimal time with numbers reaching only to ten. These artifacts—some still preserved in museums—represent one of history's stranger attempts to legislate perception itself, to convince citizens that their bodies' rhythms could be rewritten by decree.
The system limped along for about five years. In Marseille and Toulouse, decimal clocks ticked in public squares. Civil records dutifully logged births and deaths in decimal notation. At the Palace of the Tuileries in Paris, two of the four clock faces displayed this invented time until at least 1801.
Pierre-Simon Laplace, the mathematician and astronomer who would later help Napoleon reorganize French education, commissioned a personal decimal watch and used fractional days in his astronomical calculations. For scientists tracking planetary motion across weeks and years, expressing time as simple decimals of a day actually made considerable sense. The problem was everyone else.
Mandatory decimal time was suspended on April 7th, 1795—less than two years after it began. The revolution had discovered that you can guillotine a king more easily than you can guillotine an hour.
The Ancient Roots of Decimal Days
Here's the twist in this story: decimal time wasn't a French invention at all. China had been using it for millennia.
By the first millennium before the common era, Chinese timekeeping divided the day in two parallel ways. The familiar system split the cycle from midnight to midnight into twelve double-hours, each named for an animal of the zodiac. But alongside this ran a decimal system: ten shi, each subdivided into one hundred ke.
The ke—roughly fourteen and a half of our minutes—became the practical unit of daily life, used for scheduling everything from court audiences to water deliveries. Some Chinese calendars went further, dividing each ke into one hundred fen, and in 1280, the Shoushi calendar (its name means "Season Granting") added another layer: one hundred miao per fen. This created a complete decimal cascade: one hundred ke, one hundred fen, one hundred miao.
This system persisted until 1645, when Jesuit missionaries arrived bearing European astronomy and the Shíxiàn calendar. The newcomers brought with them the assumption that time should be measured in units of sixty, and Chinese decimal time quietly faded after roughly two thousand years of service.
The Gēng: Drum Beats at Night
But Chinese timekeeping held other decimal secrets. The gēng system divided the night into ten watches, each announced by the beating of drums or the striking of gongs. The word gēng itself means "rotation," referring to the watchmen who rotated through their shifts while sounding these signals.
The first gēng fell at around 7:12 in the evening—standardized from the theoretical moment of sundown. Each subsequent gēng lasted two hours and twenty-four minutes, one-tenth of a full day. The ten gēng corresponded to the ten celestial stems, those ancient Chinese symbols that combine with the twelve earthly branches to create the sixty-year cycle that still governs Chinese astrology.
In Chinese literature, characters meeting "during the third gēng" would be rendezvousing sometime between midnight and 2:24 in the morning—the darkest hours, the time for secrets and schemes.
Ten-Day Weeks
The decimal principle extended beyond hours in both France and China. Both civilizations experimented with ten-day weeks.
In China, this tradition reached back to the Bronze Age Xia dynasty, roughly four thousand years ago. The xún, as this ten-day week was called, structured months into three neat segments: the early xún (days one through ten), the mid xún (days eleven through twenty), and the late xún (the remaining nine or ten days). Japan adopted this rhythm as the jun; Korea called it sun.
The French revolutionaries, perhaps unknowingly echoing this ancient pattern, created the décade: ten days of work followed by a single day of rest. Their months contained three décades exactly. The intent was partly practical—simplifying calendrical calculations—and partly ideological, replacing the seven-day week with its biblical origins. Workers, unsurprisingly, noticed that they now received one rest day in ten instead of one in seven. The décade was not popular.
The Egyptian Connection
Even the Egyptians, thousands of years before any of this, organized their sky into decimal packages. They identified thirty-six groups of stars called decans—small constellations strung along the ecliptic, each occupying ten degrees of the celestial circle.
Every ten days, a new decan would appear on the eastern horizon just before sunrise, emerging from the glare where the sun had hidden it. The Greeks, observing this pattern, named these star groups dekanoi, from their word for "ten." A ten-day period between one decan rising and the next became a "decade"—a word we still use, though we've stretched it to mean ten years.
Thirty-six decades of ten days each gave 360 days. The Egyptians added five extra days at year's end—days outside normal time, considered unlucky—to reach 365. The number 360 wasn't chosen because it approximated the solar year; it was chosen because it divided so beautifully by so many numbers. Sixty appears again, hiding inside: 360 is six times sixty.
The Metric Dream
The French revolutionaries who created decimal time were pursuing a grander vision: the complete decimalization of measurement. Length, weight, area, volume, currency—all would submit to the power of ten. The meter would derive from the Earth itself (one ten-millionth of the distance from the North Pole to the equator along the meridian through Paris). The gram would be defined by water. The franc would divide into centimes.
Time was supposed to join this metric family. Early drafts of the metric system published in 1793 included decimal time as a full member. Joseph-Louis Lagrange, one of history's greatest mathematicians, proposed to the Commission for Republican Weights and Measures that watches should display decidays and centidays—divisions of the day into tenths and hundredths. A centiday would be fourteen minutes and twenty-four seconds: nearly a quarter hour, convenient for scheduling.
But time resisted metrification in ways that length and weight did not. The problem was biological. Human sleep cycles, hunger rhythms, and attention spans don't care about mathematical elegance. A decimal hour of 144 minutes simply felt wrong in a way that a kilogram did not.
Compromise and Failure
The French tried again in 1897. A new commission, with the mathematician Henri Poincaré as secretary, proposed a middle path: keep the twenty-four-hour day, but divide each hour into one hundred decimal minutes and each minute into one hundred decimal seconds. This preserved the familiar hour while decimating its subdivisions.
The proposal went nowhere. By 1900, it was abandoned.
The Toulouse Geographical Society had pushed a more radical alternative in the 1890s: divide the day into one hundred "cés" (from the Latin centesimum, meaning "hundredth"), each lasting fourteen minutes and twenty-four seconds. The Toulouse Chamber of Commerce endorsed this plan in April 1897. It found few other supporters.
The Second That Won
When the International System of Units finally crystallized in the twentieth century, it based its unit of time on the traditional second—not a decimal fraction of the day, but 1/86,400 of the mean solar day, eventually redefined as a specific number of oscillations of cesium atoms. The day contains 86,400 of these seconds: a number divisible by sixty, by twenty-four, by twelve, by all the ancient factors the revolutionaries had tried to abolish.
The metric system conquered space but not time. We measure distance in meters and mass in kilograms, but duration stubbornly remains an artifact of Babylonian mathematics, filtered through Greek astronomy, baked into the gears of medieval clockwork.
Decimal Time's Digital Afterlife
And yet decimal time never quite died. In 1998, the Swiss watchmaker Swatch introduced "Internet Time," dividing the day into one thousand ".beats" (pronounced "dot-beats"), each lasting 86.4 standard seconds. Midnight in Switzerland was @000; noon was @500. The system abolished time zones entirely—the same .beat occurred everywhere on Earth simultaneously, with only the question of whether it was light or dark outside varying by location.
Swatch marketed special watches displaying .beats. Third-party implementations extended the standard with "centibeats" for greater precision. The irony was delicious: this corporate reinvention of decimal time divided the day into exactly the same structure the French revolutionaries had decreed two centuries earlier. One thousand .beats equaled one thousand French decimal minutes; one hundred centibeats equaled one hundred French decimal seconds.
Swatch Internet Time faded from popular attention within a few years, though it never officially died. The company quietly stopped making Internet Time watches.
Where Decimal Time Actually Works
Despite its failures as a universal system, decimal time thrives in specific domains where its mathematical advantages outweigh its biological awkwardness.
Accountants and payroll systems routinely use decimal hours. If you clock in at 8:30 and clock out at 5:15, your timesheet might record this as 8.50 to 17.25—8.75 hours of work. Adding these numbers requires no conversion between minutes and hours; they behave like ordinary decimals.
Pilots and aviation professionals track flight time in tenths of hours for the same reason. Adding 1.6 hours to 2.6 hours gives 4.2 hours directly, without the mental gymnastics of realizing that 1:36 plus 2:36 equals 3:72, which is actually 4:12.
Scientists and computer systems frequently express time as fractional days. The Julian Date system, used in astronomy since the nineteenth century, counts days and decimal fractions of days since a reference point in 4713 BCE. January 1st, 2000 at noon was Julian Date 2451545.0; that evening at 6 PM was 2451545.25. These decimal fractions make calculating time intervals trivially easy.
Spreadsheet programs like Excel use similar internal representations: dates are stored as numbers where the integer part counts days and the decimal part represents the time within that day. Noon is always 0.5, regardless of time zone conversions or calendar reforms.
The Tyranny of Twelve and Sixty
Why did we end up with twelve hours and sixty minutes in the first place?
Twelve has factors: two, three, four, and six. You can divide twelve into halves, thirds, quarters, and sixths—all whole numbers. Try dividing ten that way: you get halves and fifths, but thirds and quarters produce messy fractions. For merchants splitting quantities, for astronomers dividing circles, for anyone working without decimal notation, twelve was simply more practical than ten.
Sixty is twelve times five, combining the factors of both bases. It divides evenly by two, three, four, five, six, ten, twelve, fifteen, twenty, and thirty. The Babylonians built their mathematics on this foundation, and their astronomical observations—recorded in base sixty—eventually became Greek astronomy, which became medieval European astronomy, which became our clock faces.
The decimal system won for counting because we have ten fingers. But for dividing—for sharing and portioning and scheduling—the older systems retained their grip.
An Hour Is Not Just a Number
The deepest reason decimal time failed may have nothing to do with mathematics. An hour isn't merely a quantity; it's a unit of human experience, calibrated by millennia of use to match the rhythms of attention and fatigue. "Let's meet in an hour" means something our bodies understand. "Let's meet in 0.042 days" means exactly the same duration but carries no felt sense.
The revolutionaries who redesigned French time believed that rational systems could reshape human perception—that citizens, given better tools, would think better thoughts. In this, they were perhaps not wrong: the metric system did eventually transform how most of the world measures space and mass. But time is different. Time is felt before it is measured. The hour existed in human experience long before it had a name.
When you next glance at a clock and see those familiar divisions—twelve hours, sixty minutes—you're looking at a compromise between Babylonian mathematics and human biology, between computational convenience and lived experience. The French tried to improve on this. China tried for two thousand years. Both ultimately returned to the rhythms that our bodies, somehow, always knew.
The Peculiar Hour Persists
Daylight saving time, that biannual disruption to our clocks, reminds us that even small adjustments to time can feel like violence against the body. Shifting one hour forward or back produces days of jet-lagged confusion—waking too early, sleeping too late, feeling perpetually out of sync.
Imagine, then, what it meant to live through the French Revolution and be told that hours no longer existed in their familiar form. That noon was now "five hours." That your lunch break lasted 0.05 days. That the church bells marking the canonical hours—those medieval divisions of the day into times for prayer—now rang at mathematically rationalized intervals that matched nothing in tradition or biology.
The decimal clock in Toulouse ran for five years. Then it stopped. The hands returned to twelve. The hour, that peculiar artifact of Babylonian stargazers, proved more durable than the revolution that tried to kill it.
Some things resist improvement.