Calendars
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Day 27: People Have Tried This Before
Yesterday I dug into the astronomical anchor problem: whether civil time should stay tied to the sun, and the complications that come with loosening that tie. Redesigning civil time at scale is extremely complex, and I don’t pretend to have the answer. But people have already tried, more than once, to do something about it. Today I want to look at those attempts and what we can learn from how each one landed.
Believe it or not, the urge to rationalize and unify time is much older than the technology that finally made it possible. A continuous atomic timescale has existed for a while now, but people were trying to redesign civil time well over a century before that.
The thread running through all of it: none of these attempts failed for technical reasons. The hard part of changing civil time has never been the engineering. It’s getting people to agree.
So, let’s take a look at the first attempt.
Decimal time, French Revolution, 1793
The French Revolution, as part of its broader push to metricize everything alongside the meter and the gram, legislated a decimal time system. A day became 10 hours, an hour became 100 minutes, a minute became 100 seconds. That’s 100,000 decimal seconds per day, each about 0.864 standard seconds.
It was elegant. It coupled cleanly with the rest of the metric system. The math was easier. It was decreed in 1793 but formally mandatory for only about six months, from September 1794 to April 1795, and almost universally ignored. Watchmakers kept making 24-hour watches. People kept reading them. The government quietly stopped enforcing it and abolished it in 1795.
The lesson, which is going to repeat: top-down imposition of timekeeping reform fails without overwhelming, immediate, individually-felt benefit. The metric system worked because shopkeepers and farmers and engineers felt the benefit at every transaction. Decimal time didn’t change anyone’s life enough to overcome the friction of relearning every clock.
Swatch Internet Time, 1998
Two centuries later the Swiss watch company Swatch tried something with a similar spirit. They invented Swatch Internet Time, a zone-free format for the internet era. A day split into 1000 “.beat” units of 86.4 seconds each, the same instant everywhere on Earth.
@500meant the same moment in Tokyo, São Paulo, and New York. The anchor was Biel Mean Time, UTC+1, the time zone of Swatch’s headquarters.It actually got adopted, briefly. The Dreamcast RPG Phantasy Star Online used .beats for scheduling international play because it sidestepped the time-zone mess of coordinating Japanese, American, and European players.
It failed because of the anchor. Tying global time to “Swatch’s HQ” guaranteed it would read as a marketing stunt. You can’t get the world to adopt a time standard whose name advertises a watch company. But the lesson here is the inverse of decimal time: bottom-up, voluntary, internet-native adoption of a zoneless format is possible. The format was usable. People used it. To grow beyond a niche it just needed neutral, institutional backing, something more like ISO than a brand.
TAI and GPS time are already working
A continuous, universal, zoneless time scale has existed for decades, and several billion people use it every day without knowing it.
GPS time started ticking on January 6, 1980, with no leap seconds. It’s currently 18 seconds ahead of UTC, and the gap grows every time UTC adds a leap second. It’s the time satellite navigation runs on, and the relativistic corrections that keep it honest are what I dug into back on Day 11. Every position fix your phone gets reads GPS time. Aviation, financial exchanges, mobile networks, they all sync to it.
International Atomic Time (TAI) is older and less famous. It began on January 1, 1958, is currently 37 seconds ahead of UTC, and is maintained by the BIPM in Paris as a weighted average of around 400 atomic clocks, each counting the cesium second we unpacked on Day 8. It has ticked without interruption and has never had a leap second. If you wanted a universal civil time tomorrow, TAI is worth considering.
What we have now is just a UTC-shaped facade. The civil layer has kept the appearance of solar anchoring. The engineering layer underneath went atomic decades ago. We already have a hybrid system.
Hanke-Henry Universal Time, 2012
We covered the Hanke-Henry calendar on Day 24, but the proposal had a second part that gets less press, and it’s worth being honest about how thin it is. Alongside the calendar, Hanke and Henry advocated abolishing time zones and putting the whole world on UTC, so everyone shares one clock. A meeting at “14:00” is at 14:00 everywhere. In Tokyo the sun is descending, in Los Angeles it’s the middle of the night, in Lagos it’s morning. The clock is the same. The sky is not.
That’s about as far as it goes. They worked out the calendar in detail, but the universal-time half is closer to a one-line aspiration: adopt UTC, drop the zones. There’s no transition plan and no account of how billions of people switch without chaos, which is telling, because that is the hard part. For all that, the proposal got real coverage, in Smithsonian, The Independent, and on CBS News, and it picked up a bit of political interest along the way. But none of that supplied the missing adoption plan, so “just use UTC” still hasn’t gone anywhere. We can’t ignore that barrier: the adoption plan is the whole problem.
Single-timezone experiments
A few countries have run partial versions at national scale. Since 1949, all of mainland China uses UTC+8, even though it spans five geographic time zones. In Xinjiang the official sunrise is around 10 AM in winter, and an unofficial “Xinjiang Time” runs two hours behind even though it isn’t legally recognized. India puts the whole subcontinent on IST (UTC+5:30). Russia keeps merging and splitting its zones for political and administrative reasons.
The lesson is that a single-zone time works, with some friction at the edges. People can live an hour or two off solar local, as long as their daily activities line up with their employers and neighbors. “Noon must equal solar noon” turns out to be a culturally negotiable constraint, not a biological one.
What all of this suggests
Five lessons from the prior attempts:
- The engineering problem is solved. TAI, GPS time, the atomic second. We have continuous universal timescales that have run for decades.
- Top-down forced reform fails. Decimal time, the French Republican Calendar. Mandated by powerful states, ignored, rolled back within years.
- Branded reforms fail. Swatch Internet Time was reasonable but tied to a corporate identity that delegitimized it.
- Single-anchor wide zones work in practice. China and India have done it for decades.
- The Hanke-Henry universal-time proposal The barrier is coordination, not technical.
If I had to draw one generalization, it’s that the path to actually changing civil time probably isn’t a sudden global switch or a top-down mandate.
It looks more like the IANA tz database: an open, voluntary, technically credible standard that earns adoption gradually, one institution and one country at a time, with a clear migration path from where we are now.
Tomorrow I want to close the loop. We already toured how strange time gets the moment you leave Earth, back on Day 12. Tomorrow’s question is the harder one: knowing all that, what would a clock for an interplanetary civilization actually have to be? The people designing it right now are converging on an answer, and it looks a lot like the reform Earth keeps refusing to make for itself.
Sources
- French Republican Decimal Time: “Decree of 4 Frimaire An II” (1793).
- Swatch Internet Time: Swatch Group historical archives and Phantasy Star Online documentation.
- GPS Time & TAI: Bureau International des Poids et Mesures (BIPM) time scale records.
- The Hanke-Henry Universal Time Proposal: Steve Hanke and Richard Conn Henry, World-Wide Time (2012).
- “One Time Zone for the World”: Smithsonian Magazine on the Hanke-Henry universal-time proposal.
- “The radical plan to destroy time zones”: The Independent on universal time.
- Calendar proposal to eliminate time zones: CBS News.
- China Time Zones: “Time in China,” detailing the use of UTC+8 across five geographical zones.
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Day 23: All the Calendars Are Just Made Up
You probably haven’t thought about this much before, but the calendar on your wall is, as a piece of civic infrastructure, bizarre. It’s the result of two and a half millennia of duct tape and wood glue.
The current global standard, the Gregorian calendar, is a 1582 Catholic correction to a 46 BCE Roman correction to a lunisolar system (a calendar that tries to track the moon’s phases and the solar year at the same time) that had been failing for several hundred years. Each “fix” was designed by people doing their best with the astronomy they had, and each “fix” was adopted on a timeline of political and religious convenience.
Hope you are ready for a lesson, because the history is much weirder than the calendar lets on. It also makes the question of “could we reform this?” feel more likely, but that is for tomorrow’s post.
The Roman mess
Before Julius Caesar, the Roman calendar was a lunisolar system with 355 days in a standard year. Because 355 days is about ten days short of a solar year, the calendar drifted forward against the seasons rapidly. The fix was an intercalary month called Mercedonius. Intercalary just means “inserted,” an extra month wedged into the year to drag the calendar back into alignment with the seasons. It was supposed to go in every two years, added by a group of priests called the College of Pontifices.
The Pontifices had to decide whether to insert Mercedonius in a given year. The decision was political. If they liked the consuls in office, they’d insert it, and the consuls got an extra month of office. If they didn’t, they’d skip it. During the civil wars of the late Republic, the system broke down completely. By 46 BCE, the Roman calendar had drifted nearly 90 days out of alignment with the seasons. Winter festivals were happening in autumn. Spring planting celebrations were happening in summer.
Caesar, after his Egyptian campaigns, came home and decided to fix it. He brought in an Alexandrian Greek astronomer named Sosigenes, who proposed abandoning the lunar cycle entirely and going to a pure solar calendar of 365.25 days, with a single leap day every four years.
To reset the seasons, Caesar made 46 BCE last 445 days. There was the standard 355-day year, plus the regular intercalary Mercedonius, plus two additional intercalary months totaling 67 more days, all jammed between November and December. Roman historians later called it annus confusionis, the Year of Confusion.
On January 1, 45 BCE, the Julian calendar took effect, and it ran more or less unchanged for sixteen and a half centuries.
The Julian drift
The Julian calendar’s bet was that the solar year is exactly 365 days and 6 hours (because of the one leap day every four years).
But the mean tropical year—the actual time it takes the Earth to complete a full seasonal orbit—is approximately 365.2422 days. If you break that decimal down:
- 0.2422 days × 24 = 5.8128 hours (5 hours)
- 0.8128 hours × 60 = 48.768 minutes (48 minutes)
- 0.768 minutes × 60 = 46.08 seconds (~46 seconds)
So the solar year is actually 365 days, 5 hours, 48 minutes, and 46 seconds. The Julian calendar assumes exactly 6 hours (which is 5 hours, 59 minutes, and 60 seconds). Subtract the true solar year from the Julian assumption, and you find the Julian year is too long by exactly 11 minutes and 14 seconds.
That doesn’t sound like much. Over 128 years it accumulates to a full day. Over 1,257 years, the span from the Council of Nicaea in 325 CE (where the Catholic Church anchored its calculation of Easter to the spring equinox) to the late sixteenth century, it accumulated to about 10 days.
By 1582, this had become a real problem. Nicaea had fixed the spring equinox to March 21. By Pope Gregory XIII’s time, the physical equinox was happening on March 11. Easter, which is anchored to the equinox, was steadily drifting later into the year. Without a fix, Easter was going to walk forward into summer and the Catholic Church wasn’t going to let the ressurection of Jesus Christ drift all over the place. Time to fix the calendar!
October 1582
The Catholic Church commissioned a calendar reform led by an Italian physician and astronomer named Aloysius Lilius and, after his death, finished and defended by a German Jesuit named Christopher Clavius. Clavius’s defense of the new system, is one of those documents nobody reads but quietly underwrites the modern world.
The reform did two things.
It deleted ten days. Pope Gregory XIII’s papal bull Inter gravissimas declared that Thursday, October 4, 1582, would be followed directly by Friday, October 15, 1582. Five through fourteen simply did not exist. The days of the week continued unbroken, Thursday to Friday, but the dates jumped. This realigned the calendar with the physical equinox.
It changed the leap year rule. Under the Julian system, every year divisible by 4 was a leap year. Gregory’s reform added an exception. Century years are not leap years, unless they are divisible by 400. So 1700, 1800, and 1900 were not leap years. 1600 and 2000 were. This drops three leap days every four hundred years, bringing the mean Gregorian year to 365.2425 days. Long by only 26.8 seconds per year, which is small enough that the next correction won’t be needed for over 3,000 years.
It’s an elegant fix. It also went over about as well as you’d expect a Pope’s calendar reform to go in Protestant Europe.
Adoption was a mess that lasted four hundred years
Catholic countries adopted on the day Rome decreed. Spain, Portugal, Italy, Poland, France (with a December skip instead of October). Protestant Europe refused. England, by then deep in its Protestant identity, was not going to take a calendar reform from “the Antichrist in Rome.” For 170 years, traveling between England and France required adjusting your calendar by ten days, and after 1700, eleven days.
England finally gave in in 1752, when Wednesday, September 2, 1752, was followed by Thursday, September 14, 1752. The American colonies came along. There’s a famous story about street riots demanding “give us back our eleven days.” Most historians now think the riots were largely embellished from a satirical Hogarth painting, but the eleven-day jump was real.
Russia held out longest. The Russian Orthodox Church refused the Gregorian calendar straight through the late Russian Empire. It took the Bolshevik Revolution to finally switch civil time. Lenin decreed the change in early 1918, with Wednesday, January 31, 1918, followed by Thursday, February 14, 1918. Thirteen days deleted. This is why the “October Revolution” of 1917 actually happened on what we now call November 7. The Russian Orthodox Church still uses the Julian calendar for liturgical purposes, which is why Orthodox Christmas falls on January 7 in countries that converted civilly but not liturgically.
And then there’s Sweden. Sweden tried to be clever. In 1700, they decided to make the transition gradual. Drop every leap year between 1700 and 1740, no jumps. They successfully skipped leap day 1700. Then the Great Northern War broke out, the bureaucracy got distracted, and they forgot to skip leap years 1704 and 1708.
This left Sweden on a unique calendar. One day ahead of Julian, ten days behind Gregorian, aligned with no one. King Charles XII, recognizing the system was a mess, decided to revert to Julian. To do this, Sweden added an extra leap day to 1712, creating February 30, 1712, the only documented February 30 in civil history.
Sweden finally adopted Gregorian normally in 1753.
The point
I’m spending a couple of days on calendars to illustrate it’s just a mess as with all our methods for representing time. The Gregorian calendar isn’t optimal. It is a sixteenth-century Catholic patch on a first-century-BCE Roman patch on an even earlier patch. What we use today is chronological kludge.
None of this had to be this way. It is what it is because of historical accident: which rulers held power, which church each country answered to, and how long each was willing to take a calendar from Rome.
This matters because it means the idea of replacing the Gregorian calendar isn’t crazy. The Gregorian calendar replaced the Julian which replaced the Roman which replaced a number of earlier systems. There is no reason in nature that the calendar in 2200 will look like the one in 2026.
Several serious people have tried. The League of Nations debated calendar reform in 1931. Eastman Kodak ran on a thirteen-month calendar for sixty-one years. There’s a current proposal, from a Johns Hopkins economist and an astrophysicist, to switch the world to a perpetual calendar where every date falls on the same day of the week, forever.
Tomorrow: the calendar that almost was.
Sources
- The Julian Reform: Richards, E. G. Mapping Time: The Calendar and Its History. Oxford University Press, 1998.
- Solar Year & Julian Drift Calculations: Meeus, Jean. Astronomical Algorithms. Willmann-Bell, 1991.
- Gregorian Calendar & The 10-Day Skip: Clavius, Christopher. Romani calendarii a Gregorio XIII restituti explicatio. Rome, 1603.
- English Adoption (1752): Poole, Robert. Time’s Alteration: Calendar Reform in Early Modern England. UCL Press, 1998.
- Sweden’s February 30: Bauer, R. W. Calender for Aarene fra 601 til 2200. Copenhagen, 1868.
- The Russian Calendar Shift: “Decree on the Introduction of the Western European Calendar,” RSFSR, 1918.
- The Eastman Kodak Calendar: The Journal of Calendar Reform, 1930s-1950s.
- The Hanke-Henry Permanent Calendar: Proposed by Richard Conn Henry and Steve H. Hanke at Johns Hopkins University.
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