Metric Time

Aside from you chronically late people, we all know how time works:


This system is okay. But also, it’s kind of crazy.

Why 60 minutes per hour? Why 60 seconds per minute? It goes back to Babylon, with their base 60 number system—the same heritage that gives us 360 degrees in a circle. Now, that’s all well and good for Babylon 5 fans, but our society isn’t base-60. It’s base-10. Shouldn’t our system of measuring time reflect that?

So ring the bells, beat the drums, and summon the presidential candidates to “weigh in,” because I hereby give you… metric time.


Now, this represents a bit of a change. The new seconds are a bit shorter. The new minutes are a bit longer. And the new hours are quite different—nearly two and a half times as long.


So why do this? Because it’d be so much easier to talk about time!

Here’s one improvement: analog clocks are easier to read. At first glance, the improvement may not be so obvious—we’ve simply reshuffled the numbers a bit.


But notice, the minute hand makes more sense now. When it’s at the 2, we’re 20 minutes past the hour. When it’s at the 7, we’re 70 minutes after the hour. And so on.


Second, times are no longer duplicated. For example, instead of needing to distinguish between 6am and 6pm, we can simply say “2:50” and “7:50.” (This is, of course, how “military time” currently works.)

Third—this is a big one—the time tells you how far through the day you are. The time 2:00 is exactly 20% of the way through the day. At 8:76, we’re exactly 87.6% of the way through the day.


Fourth, consider the moment when we’re 99.9% of the way through the day. In the new metric system, we get to watch the clock roll from 9:99 back around to 0:00. Isn’t that nicer and more conclusive than 11:59pm rolling around to 12:00am?

Fifth, it’s so much easier to talk about longer times. Two and a half days? That’s 25 hours. Three days and 6 hours? That’s simply 3.6 days. Since an hour is now a nice decimal fraction of a day, these conversions become easy.

Will there be adjustments to make? Certainly! But the adjustments are half of the fun.

Let’s start, as all good things do, with television. Whether you enjoy half-hour sitcoms or hour-long dramas, the length of your favorite shows is probably going to change. Why? Because, under our new system, what we now call “half an hour” will be 20.83 minutes. What we now call “an hour” will be 41.67.


There’s nothing magical about these “half-hour” and “hour” lengths, obviously. They were chosen simply because they were nice round numbers. But under the new system, they aren’t! Since it’d be silly to divide the TV schedule into 21-minute intervals, presumably television networks would tweak the lengths to go more evenly into an hour.

If so, they’d have two choices: 5 blocks per hour (i.e., two dramas, plus a sitcom), or 4 blocks per hour (i.e., two dramas).

If you choose the former, shows will be 4% shorter than today, leading to accelerated storytelling. (It’s the same change that’s unfolded over the last 20 years, as increased ad time has squeezed the shows themselves to be shorter.)


And if you choose the latter, shows will be 20% longer. They’ll perhaps unfold at a slower, more cinematic speed. Either way, expect the pacing and rhythm of TV shows to change.

Sports run into the same issue. Football will probably opt for four quarters of 10 minutes each, which shortens the game by 4%. Expect slightly diminished scoring as a result. (And, if we’re lucky, diminished concussions.)


Hockey, meanwhile, might go for three periods of 15 minutes each, which actually makes the game 8% longer. It might give someone a chance to tackle Wayne Gretzky’s scoring records (but then again, probably not—he’s way out of reach right now).


I’d expect soccer to select two halves of 30 minutes each, which (as with American football) shortens games by 4%. If you thought soccer was too high-scoring already, you’re in luck (and also in a very small minority, I suspect).


When it comes to sports, the lengths of games won’t be the only thing changing. We also need to reconsider record running times.

Usain Bolt’s world-record for the 100-meter dash (currently 9.58 seconds) would be, under the new system, 11.09 metric seconds. Doing the 100m in 11 metric seconds might be achievable in the future, but 10 seconds? Perhaps never. (That’s the equivalent of 8.64 of our seconds!)

What about the mile? Well, it’s a little funny to imagine a world with metric time still worrying about that strange unit of distance (5280 feet? Really?), but the famed 4-minute mile would correspond to a 2.78-minute mile.

This is weird because, for top runners in the 1940s and 1950s, the barrier to running a 4-minute mile may have been less physiological than psychological. Would the 2.8-minute mile have felt as intimidating? Would the 3-minute mile? Perhaps it’d be the 2.5-minute mile, seeing as the current world record (3:43 in our old system) is 2.58 metric minutes?


And we might as well mention the marathon, where the world record time (currently 2:02:57) is now under an hour: 85 minutes, 38 seconds. I suspect that the 1-hour marathon would be a real badge of honor, something that every distance runner aspires to.

Leaving sports aside, what about food?

Restaurants would open for breakfast at perhaps 3:00 or 3:50. (Of course, coffee shops like Starbucks might open as early as 2:50.)

You’d get lunch around 5:00—that is to say, noon. Under our current system, I feel silly eating before 11:30, which is 4:80 under the new system. But I wonder—would I feel comfortable grabbing lunch at 4:75? Perhaps even 4:60 (even though that’s earlier than 11am under our current scheme)?


Eating is psychological, and how we number our hours might steer our behavior.

As for dinner, I suspect 7:50 to 8:00 would be the preferred time (although the famously late-eating Spaniards might hold off until 8:75 or 9:00).

Other numbers change, too. Take speed limits: the typical 65mph limit on many highways translates to 156 mph under the new system; I suspect we’d see that bumped up to 160 mph or down to 150 mph for the sake of roundness (which translates to 66.7mph or 62.5mph under our current system).


The speed of sound? Not 340 meters per second any longer; it’s now just 294 meters per second. Meters haven’t changed, of course, but seconds have gotten shorter!

And the speed of light? Unfortunately, we lose the lovely number 300 million meters per second; instead, it becomes roughly 260 million meters per second.

Speaking of light, on the equinox, you get 5 hours of light and 5 hours of dark.

The winter solstice is pretty grim: in London, you’d see just 3 hours, 25 minutes, and 25 seconds of daylight.

The summer solstice is nice, though: London would get 6 hours, 93 minutes of sun.


Okay, time to come clean: I propose this without a single iota of seriousness. It’d be insane to ditch our current system. We’re used to it. We’ve agreed upon it. We’ve built our lives around it. The hassle of a change far outweighs the gains.

But I still love the thought experiment. It asks you, in some small way, to reimagine your life. How do you spend your time? How do you measure the success of a day? When you plan your hours, are you conceding to the arbitrary dictates of a quirky clock, or are you truly giving your tasks the time that they deserve? If I scrambled your sense of time, relabeling all your moments, would it change the way you feel about them? Do the numbers we assign to times matter? Or are we just scratching lines on the shifting dunes of eternity?

43 thoughts on “Metric Time

  1. I think it would totally be worth the hassle. I’ve long since imagined about using a decimal time system, and the benefits. I think we would get used to it pretty fast. Now if we could find a way to make weeks 10 days and somehow split the year into 10 months, we could really make some progress.

    1. I’ve thought about the months issue before – I think the best option is alternating months of 36 and 37, where each month has 5 weeks of 7 days, plus 1 or 2 bonus holidays at the end. The bonus holidays would have different names (rather than Monday/Tuesday/etc.), and wouldn’t be part of the standard week.

      If only the earth’s rotation fit more nicely into its orbit!

      1. Isaac Asimov has an essay on metric time where he proposes a similar system: 13 28-day months (to fit evenly with a 7-day week) plus one bonus day per year (which would not be a day of the week).

  2. This idea is not new. In particular it was proposed as a time system by the First French Republic after the French Revolution. Unlike the other elements of what was to become the SI, this decimal time did not stick.

    1. True! Another failure was the gradian, which defined a right angle as 100 gradians (as opposed to 90 degrees). Pretty good overall success, though, I’d say.

      1. The day as unit makes a lot of sense, though. Imagine we move off-Earth to live on a population of many cylinder-ships (each a spinning cylinder, a world-in-a-bottle, whose spinning gives a gravity that holds the interior onto its outer skin). Each community can chose whatever schedule and system it wants, for day and night and for any simulation of seasons they may trouble to make; but the living things they tend (themselves, their children, their pets, their food, flowers and raw materials) have all evolved to a day-night cycle and a season cycle; they’re fairly well optimised for the particular durations those have on Earth. So we’ll likely stay with the day and year approximately as they are; we may make minor adjustments, in so far as living ecosystems work tolerably well when so adjusted, but we’re unlikely to deviate far from what the Earth is currently doing.

        Imposing a nice wound power of ten times the second would probably break ecosystems in such a scenario; and we simply can’t get away from the day as long as we continue living at the bottom of a (moderately) deep gravity well.

        The week derives from the moon, with the month as a compromise between it and the year (with some astrology probably playing a part somewhere in the mess). All our other units of time are our own inventions; we use them only by convention and their subdivisions are rather arbitrary. The day and night were each divided into a dozen parts; we eventually stopped using sunset and sunrise to define those, dividing the day into two dozen equal hours. Astronomers, needing precision in time-keeping to record their observations accurately, subdivided the hour “minutely” into 60 equal parts; later, when even this minute (think: “my newt”, not “minit”) subdivision proved inadequately precise, they made a second “minute subdivision”; whence came the name, “second”, of their unit; which we now subdivide by powers of ten. The initial subdivision into day and night was natural; but, after that factor of two, all the other factors are artefacts of the cultures that chose them; and we’d let the two dozen slip out of sync with the original subdivision into two, for the sake of regularity, long before we began sub-dividing its hours.

        However, I would not use the terms “hour”, “minute” and “second” for the metric subdivisions of the day; I would use the appropriate SI quantifiers and accept the practicality that popular culture would continue to speak of hours, minutes and seconds. Before long, the vernacular would drift to using them imprecisely; an hour of four-and-a-sixth centidays would soon enough mean four, or perhaps a bit more, centidays. The 694 and a bit microday minute would soon enough blur until either the milliday or half of it replaced most uses of it. The second is between eleven and twelve microdays; so it might well end up being colloquially used to mean ten of them.

        Of course, if we’re going to get rid of the second from our system of units, this is the point at which to take a long hard look at our other units and think what else might be handy. Clearly we scrap, also, the metre in favour of the light day; as that’s roughly the circumference of Neptune’s orbit, we’ll want to use subdivisions of it, naturally. The light picoday is 25.9ish metres (85 ft); the light femto-day is thus 25.9 mm, a smidgin over an inch; that’s a moderately small unit, but practical enough. It would surely, soon enough, acquire the nickname inch, at least (or a name meaning “thumb” in several languages whose speakers gave up using such a unit a over the last few centuries). That takes care of time and length.

        Since that leaves us with the speed of light as our unit of speed, our units of momentum and energy are going to be our unit of mass times that speed and its square; if we want to avoid a ludicrously big unit of energy, we thus want a moderately small unit of mass. For example, the Planck mass, sqrt(c.h/G) = gram/18327, is of the right sort of order for this; unfortunately, it involves Newton’s constant, G, which is tricky to measure accurately.

        Using G, day and time we could get a unit of mass; but it works out at 34.89e36 metric tonnes; The Milky Way has a mass of around 110 of these, so this might be a handy unit for cosmologists, but it’s not much good to the rest of us; and, besides, we don’t know G accurately enough. We could use Planck’s constant, h, instead: we know that tolerably accurately, but the mass unit it gives, with day and light-day, is gram/11.7e51, which is even more ridiculously tiny than the previous candidate was ridiculously huge.

        IIRC, we’ve recently come through a redefinition of the kg in terms of the atomic mass unit, AMU, via effectively defining a numeric value for Avogadro’s constant (which is just under 2^{79}); in any case, the AMU is fairly precisely known (and we can make perfect spheres of single-crystal monoisotopic silicon with spectacular precision), so I’m confident we can use a unit based on some suitable multiple of the AMU. Naturally, I want to chose a nice tidy power of a thousand; and 1e18 AMU (the exa-AMU or EAMU) come out around gram/6e6. That gives a momentum, the light-EAMU, of nearly a half kg m/s, and an energy of nearly 150 MJ. The fact that the mass unit sounds like a big bird at least means it’s pronounceable.

        We could use the resulting energy unit to measure temperature (treating Boltzmann’s constant as a mere unit conversion factor), albeit it corresponds to almost 11e30 K, so we’d want a 1e-30 quantifier to apply to it to give a practical every-day unit around 11 K. Nothing prevents us, however, retaining Kelvin as unit, with Boltzmann’s constant (expressed in the new units) as effective conversion factor.

        The impedance of free space, about 377 Ohm, then completes our system of base units (implying charge, current and so on). The resulting current unit is just over 2 Ampere, so fairly practical (albeit, like the Ampere, a bit big). That, of course (with day as time unit) makes the charge unit rather big, about 185 kiloCoulomb; but that’s good, given how big our energy unit is, as it keeps our voltage unit from being too big; it comes out at about 807 Volts, so we’ll be using domestic power supplies at one or two sevenths of that unit; maybe we can even all standardise on a single value, worldwide, while we’re at it.

        So, if you’re going to consider a radical change of units, do it properly: use the day and light-day, use SI quantifiers to get the practical units we’ll need (let colloquial usage find aliases to some of them on its own terms) and extend with a small mass unit (so that the energy unit isn’t too huge), on the scale of Planck’s (but with a rounder number, in place of Avogadro’s, as scaling from AMU), and pull in the impedance of free space for your electromagnetic units.

        (Yes, I do think about these things way too much for my own good 😉

  3. I would support this change! Also, in order to keep references to the new system distinct from references to the old system, we should use mours, mminutes, and meconds, for the new system. 😛

  4. What about the totally crazy and base-less (in the mathematical sense) calendar? Why are there 7 days in a week? (That’s annoying, 7 is prime.) Why can’t we agree on how long a month is or how many weeks there are in a month? It makes all sorts of things in accounting and time keeping quite annoying.

    1. Agreed. See my reply to Hungry Dog’s Lair above for the best idea I’ve come up with – although you’re right that the 7-day week is weird. Also deeply ingrained in our culture, with the 5-day workweek and 2-day weekend!

      1. The problem you have with measuring time is that you want it to line up with some astronomical events – length of an Earth mean solar day (or true solar day?), length of an Earth tropical year (or a sidereal year?), length of a lunar orbit (by some measure), etc. It’s a complex problem to which there cannot be a simple answer, unless it’s a wrong answer.

  5. In Joan D. Vinge’s novel The Outcasts of Heaven Belt, terrestrial time is irrelevant (the characters live in an asteroid belt in a different stellar system), but the SI second still matters — it’s the basis of all science and engineering, after all. So time is organized metrically from the bottom up instead of the top down. If you’re more than a kilosec late for an appointment, it’s a bad thing; a megasec is a reasonable time to work on a project before reporting to your boss; a marriage that lasts a gigasec is doing very well.

    1. I like that! My wife’s grandparents are well past two gigasecs at this point. And I’ve been at work for a kilosec today, but am still replying to blog comments…

      Relatedly, I was devastated this December after I realized I’d missed celebrating my 10,000th day of life. (I’m not expecting to make 100,000.)

  6. I’m glad you’re only tongue-in-cheek on this. Decimal time is a horrible idea, especially if you extend it beyond a day. 10 days to a week, great!, 10 weeks to a month… 100 day months seems a bit long but I’ll run with it, 10 months to a year… um nope doesn’t work.

    I have a big problem with the trend in the last few decades of scientists pushing the metric system for non-science purposes… and this is coming from a scientist. Every few years someone brings up trying to convert the US to metric distances or to use Celsius for weather etc. Here’s the thing, all metrics should be chosen primarily for their usefulness and secondarily for cost of change/general acceptance. For example, for weather (layman not scientific) Fahrenheit makes much more sense than Celsius (at least for the bulk of North America/Europe/North Asia) because 0 degrees pretty well corresponds to the coldest day of winter and 100 to the hottest day of summer. Just like that decimal time might have some scientific value (as some have already mentioned above.) but it should be used solely for scientific reasons never for day to day stuff because it doesn’t make sense.

    And now to further alienate myself. I think the current metric system needs to be replaced for scientific use by metrics derived from universal constants. Probably the Planck system: but even switching from Celsius to Kelvin is a step in the right direction.

    1. How would it work with the 24 time zones? In terms of 100 months etc. nobody would want to do that. The rate at which the earth revolves around the sun is less relevant than the actual rotation of the earth itself daily. Who would want a fraction of an earth rotation in one day and a fraction of an earth rotation in another day? Don’t forget An earth year is 365.25 days.. So every third year the earth’s times would be off by 3/4ths just to self-correct the fourth year. Nobody cares to do that.

  7. Greetings Math with Bad Drawings!

    May I use this post with my grade four class and share it with a group of teachers at a workshop?


    James Mika Bright’s Grove Public School Bright’s Grove Ontario ________________________________________

  8. Shouldn’t time be written as 7.20 instead of 7:20 in metric time? If I recall correctly, the “:” sign was originally put there to clarify that it was not written in decimal scale.

  9. > Meters haven’t changed, of course, but seconds have gotten shorter!

    Changing the second would actually mean altering meters, amperes, and candela as they all refere to the SI second. For example SI meters are defined by the distance light travels (in vacuum) in a specific time.
    Too bad kilogrammes aren’t affected. That could cause a much bigger mess. 🙂

    1. That makes math easy, but limits the number of ways you can factor a day.
      The problem is base ten. We should have developed a base twelve metrology. Then we’d have 10z hours in a day, 100z minutes in an hour, 100z seconds in a minute. No tedious unit conversions, but there’d still be lots of ways to factor the day.

  10. I considered, but ultimately rejected it. So did the French in 1789.
    Ten has few factors. Thus while metric time makes math easy, it leaves few ways to divide up the day.
    I’m in favour of a dozenal metric clock like this:
    I argue for that here:
    I argue for base twelve here:

  11. Coming in a bit late here, but I thought I would weigh in.

    I agree that this system would make much more sense overall rather than using a system that was handed down to us by the Babylonians (base 60 system) combined with the ancient Egyptians (base 12). It’s messy and awkward. In some instances, we already use semi-metric (or decimal) time. Some time clocks have been using it for years (6.98 rather than 6:59), it’s easier for the computers and/or the people using them.

    I would also add that starting the 0th hour in the middle of the night doesn’t make sense. If we are making changes the to system, let’s correct this as well. (“Boy, we were up late! See you tomorrow?” “Sure, but it’s 1:30 am. Do you mean the real tomorrow or just later today after we go to sleep and wake back up???”). Let’s start the day at a fairly mutual time that most people start their day, sunrise. As this changes throughout the year, take an average and go with it. I would suggest around 6:00 am AT (anachronistic time) (BTTT??? Behind the times Time? LOL).

    10 months is the way our system used to be until the Romans got their hands on it. Hasn’t anyone wondered why OCTober isn’t the eighth month? It was, but then two different Roman Caesars decided that they should get their own month and stole days from other months to do this. The two? Julius and Augustus, of course. AND they made sure that their months were among the longest. Do away with them, go back to 10. 10 months, alternating 37-36 days, have February line up as one of them with 36, and then every 4 years, we can give it the extra day, just like we do now.

    I live in the USA and I believe that we should be on the metric system, just like the rest of the world. The English system is archaic (even the English have essentially abandoned it!) and difficult to work with. A lot of Americans already are fairly familiar with metric and use it in their every day lives, even if they don’t realize it. Everyone here knows how big a 2 liter bottle of pop is, a lot of mechanics are familiar with a 10 or 12mm wrench due to them being commonly used internationally (where even a lot of our American-made cars are manufactured), drug dealers deal in grams quite a lot, most people are familiar with Celsius (0 – 100 freezing to boiling water). People say that this would be an almost impossible change to make, but I don’t believe that for a moment, just about everyone else in the WORLD has done it, but we CAN’T?!? People don’t LIKE change, true, but we need to quit being “fat, lazy Americans that will pay extra just to have things convenient” and man up.

    Change everything to a logical, metric World Standard (time, weight, height… everything) and move forward from our near-sighted forebears. It’s time to start the future.

  12. Why would you change to metric time without standardizing lengths to metric as well?
    60 mph would become 231.74544 km/h. Lets round it to 230.
    65 mph would become 251.0568 km/h. Lets round it to 250.
    70 mph would become 270.3696 km/h. Lets round it to 270.

  13. If we would do metric time then why would it be 0 to 10 instead of 0 to 20? You might say like to think what percentage of the day has passed or something like that but then the same reasoning could be used to think about what percentage of the half-day has passed i think.

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