Standards
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Day 29: It's All The Same Problem
We’re twenty-nine days into this. I’ve thrown twenty-eight different time problems at you. Sundials, cesium fountains, leap seconds, Unix epochs, DST, lunar time, the Y2038 bug, calendar drift, time zones in Nepal. Twenty-eight posts. Twenty-eight things that should not be problems but are.
Today I want to tell you the thing I’ve been quietly noticing the whole series and never once called out by name.
They’re all the same problem.
Every single one. Same pattern, twenty-eight times, wearing twenty-eight different outfits. I’m going to name it today. Then I’m going to do something annoying with the schedule, which I’ll get to at the end.
Speed recap (skip if you’ve been reading along)
Week 1, what time is. Philosophers spent a century arguing about whether the present is real or whether all moments coexist. Einstein answered them. Your brain disagrees with both. Your “now” is a two-second hallucination your prefrontal cortex glues together from inputs that arrived at different speeds. Most animals don’t even live on the same scale of now you do.
Week 2, how we measure it. Sundials to water clocks to pendulums to cesium fountains to optical lattice clocks. We measure time to a part in 10^18, the most precise measurement humanity makes of anything. And then we strap leap seconds onto it.
Week 3, how computers handle it. Unix time pretends leap seconds don’t exist. NTP synchronizes the internet to within a millisecond of UTC, mostly because one guy at the University of Delaware refused to let it die. ISO 8601 prevented an entire generation of date-format wars. Time zones aren’t 24, they’re 38 and counting, and at least one sits at +5:45 for reasons.
Week 4, the cracks. Leap seconds crashed Reddit and Cloudflare. DST kills people, measurably, twice a year. Calendars are 2,000 years of patches on patches. The World Calendar almost passed the UN in 1955 and got killed by religious objections. The Hanke-Henry proposal solves the religious problem and has no political mechanism.
Week 5, the punch line. Einstein made “now” frame-dependent. Atomic time and astronomical time have been quietly drifting apart since 1972. Clocks on the Moon run 58 microseconds per day faster than clocks on Earth, and the White House gave NASA a 2026 deadline to figure out what to do about it. Mars’s day is the wrong length, and the people running rovers there go nocturnal in shifts.
Twenty-eight different stories. Each one feels like its own little disaster. Each one is its own little disaster.
OK. Now look at all of them at once.
A pattern emerges
Every single one is the same shape.
Too many time systems pretending to be one.
That’s it. That’s the diagnosis. Let me run it back.
- Wall clock time pretends to be solar time. It isn’t. It’s solar time, offset up to an hour by your time zone, then offset another hour by DST. Three systems. Presented as one.
- UTC pretends to be a uniform atomic timescale. It isn’t. It’s atomic seconds with manual leap-second patches jammed in whenever the Earth misbehaves. Two systems. Presented as one.
- Unix time pretends to be UTC. It isn’t. It’s atomic seconds with the leap seconds quietly deleted. Two systems. Presented as one, with the inconvenient one erased.
- The Gregorian calendar pretends to track the seasons. It almost does. The seasons drift against it at 26 seconds a year. Two systems. Presented as one.
- Earth civil time pretends to be the universal frame. It isn’t. The moment people start living on the Moon it won’t even pretend. Two systems. Presented as one. Third one inbound.
Every outage we’ve documented in this series is what happens when the layers diverge.
The 2012 Linux meltdown was the atomic layer screaming at the civil layer through the leap-second seam. DST mortality is the social layer dragging the biological layer somewhere it doesn’t want to go. Y2038 is the storage layer running out of room to lie about the coordination layer. The 2019 Brazilian DST cancellation broke every calendar event saved in local time, because the saved-time layer disagreed with the rule layer.
It’s the same bug everytime, just dressed up in a different costume.
They’re all just one problem we keep meeting, just at different layers.
What the shape of a fix looks like
I’m not telling you the full answer today. But the shape of it appears when you can see the pattern. The key is to stop letting the layers pretend to be each other.
That’s the whole design I laid out yesterday: one coordination layer underneath, atomic, uniform, no leaps, no zones, no calendars baked in, the thing computers and GPS and finance and navigation already run on, with known relativistic offsets if you leave Earth. Then a thin civil layer on top for humans: local, day-night aware, with the calendar and zones living up here as display only. The civil layer is computed from the coordination layer plus your local context. It’s never stored as the source of truth.
The whole point is that the layers don’t pretend to be each other. The coordination layer doesn’t pretend to track the sun. The civil layer doesn’t pretend to be a database timestamp. When two layers disagree, only the display changes. The stored truth is invariant.
Some flags I’m planting
Before someone accuses me of refusing to commit, three things I’ll say flat out.
Time zones are stupid. Not “annoying.” Not “a useful tradeoff.” Stupid. Thirty-eight of them. One sits at +5:45 because someone wanted to be 15 minutes off from India. Half of Australia runs on a different schedule than the other half. Indiana spent decades arguing with itself about which zone to be in. China is one country and one time zone across five solar hours. The whole point of a time zone is supposed to be “the sun is roughly overhead at noon.” We’re not honoring that contract anywhere. Some American zones put solar noon as late as 1:30 PM in summer. We’re paying the entire complexity cost of having zones and not actually getting the thing zones were invented to do. Time zones are a 19th-century can we’ll keep kicking well into the 21st.
DST is dumb. Day 21 was the whole case. Heart attacks, strokes, car crashes, a 1% increase in residential electricity use, no farmers asking for it, no voters asking for it, no science defending it. We do it because two camps in Congress can’t agree on which fake time to settle on. Not relitigating. Just doubling down.
UTC is on “borrowed time” and it knows it. UTC the protocol is fine. UTC the way it shows up in your daily life has time zones bolted on through the “+5” notation, has DST schedules layered on top, and (currently) has leap seconds duct-taped in whenever the Earth misbehaves. UTC itself is a leaky abstraction. It tries to be the coordination layer and the civil layer at the same time, and the cracks have already begun to appear. Abolishing the leap second was UTC quietly admitting it can’t be both, and after 2035 the civil-display half of its job becomes somebody else’s problem.
Now the things I’m not claiming.
I’m not claiming any one proposed solution is right. Decimal time failed. Swatch Internet Time failed. The World Calendar failed. Hanke-Henry probably won’t pass. The path forward, whatever it ends up being, has to be designed with those failures in mind. Top-down reform fails. Branded reform fails. The thing that has actually worked, where anything has worked at all, is open standards adopted gradually by institutions that found them useful. The way ISO 8601 became universal without anyone forcing it on anybody.
And I’m not claiming this is a five-alarm fire. The system mostly works. The bugs are real but tolerable. Civilization will not collapse if we don’t fix this.
But it was built for an Earth-bound, slower, less precise world, and it’s being asked to do things it was never designed for.
Lunar Coordinated Time is due by the end of 2026. The system that mostly works is going to be asked to do more, and we are going to need a better one.
Tomorrow
OK, first, I need to apologize.
Day 30 would normally land tomorrow. That’s where you would typically end a series called “30 Days of Time”. But tomorrow I’m going to break that promise on purpose, and here’s why.
I’ve been working on something while writing this series. The whole reason this synthesis exists is that this pattern is the thing I’ve been trying to design a solution for. I have a draft of an answer. I have a reference implementation. What I don’t have is anything finalized that I can actually point you toward.
I’d rather get it right than ship Day 30 tomorrow with a half baked idea. I want the Day 30 payoff to be a well thought-out draft of a unified time standard, not a rushed sketch. I don’t know how long that takes. Probably a couple of weeks but maybe longer.
So Day 30 is coming, I promise. No specific date. When it lands, it’ll come with something formalized that’s actually worth pointing you at.
Thank you for sticking with me for twenty-nine days. Day 30 won’t be a manifesto. It’ll be informative, but it will also be a call to action.
So, the most important post in the series is NOT the one I’m not going to publish tomorrow.
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Day 28: What an Interplanetary Civilization Needs From a Clock
A couple of weeks ago, on Day 12, I took the tour. A Mars day is 39 minutes too long. The Moon’s clocks run about 58 microseconds a day fast. A round trip to Voyager takes two days. Astronomers already juggle a whole family of relativistic coordinate timescales to keep it all straight. If you want the details, it’s there.
Today I want to ask the question that tour sets up but doesn’t answer. Given all of that, what would a clock for an interplanetary civilization actually have to be? Not the problems. The design.
And this isn’t a thought experiment. Right now, at NASA, ESA, and the White House Office of Science and Technology Policy, people are building the first piece of it, with a 2026 deadline. The design question has a clock running on it, which makes it worth getting right.
Why we can’t just ship Earth time
The instinct is to take what works here and copy it outward. It doesn’t survive the trip.
What we call “time” on Earth is two different things welded together. There’s a coordinate layer, the uniform atomic tick underneath UTC, and there’s a display layer: the time zones, the calendar, daylight saving, the assumption that 12:00 means the sun is roughly overhead. We never separate them because we never had to. Everyone who matters lives on one planet, rotating once a day, so the weld holds.
Leave the Earth’s surface and it breaks down. The Moon’s day is four Earth weeks long, so “noon” is useless as a unit of human activity. Mars’s day is close to ours but drifts a full cycle out of phase every forty days. A clock deeper or shallower in a gravity well ticks at a measurably different rate. The display layer assumes things that are only true on Earth. The coordinate layer is the only part that travels.
How you’d actually design it
Here are my principles that I’ve come up with on designing a time system for interplanetary civilization. Call them pillars. None of them care which body you happen to be standing on.
1. A coordination layer underneath everything. One shared timescale that every machine, log, and database syncs to. This is the part we already do well: TAI and the timescales built on it are a solved problem. The coordination layer is non-negotiable, because without a single shared reference nothing else holds together.
2. Uniform ticks, and precision matters. The tick has to be uniform, repeatable, and stable, with an error bar low enough that the rate doesn’t measurably change over thousands, ideally hundreds of thousands, of years. The cesium second clears that bar today. It won’t be the last word: optical lattice clocks are already orders of magnitude more precise, and the definition of the second may eventually move to them. How you reach the precision can evolve, by averaging more clocks or adopting better physics. The principle doesn’t. Uniform ticks, and the smaller the error bar the better.
3. A civil layer shaped around people, not physics. On top of the count, each body gets a civil layer for the humans living on or near it: a local “day” from whatever its rotation gives, a calendar, zones, whatever fits. There is no universal right answer here, and that is the point. The civil layer is supposed to be local and negotiable. Getting it right is also the whole game for adoption, because people don’t adopt a coordinate count. They adopt the layer they read off the wall. Calendars are a good example. Everything we dug into on Day 23 and Day 24 lives entirely at the civil layer. The coordination layer doesn’t care about calendars, it just counts. We can change the calendar without changing how we measure time.
4. Store it as integers, not strings. Underneath, time should be a single growing integer, a count of ticks from a fixed origin. Unix time got this right: one number, trivially comparable, trivially sortable, no parsing. The moment you store time as a string like “2026-06-14T10:00,” you have handed every machine a parsing-and-timezone problem it never needed. Strings are for display. The truth is an integer.
5. Pick the zero point deliberately. Every count needs an origin, and the choice is more loaded than it looks. We touched on it on Day 10. Unix picked midnight 1970. Others anchor to a calendar epoch, a mission start, a physical event. There’s a real argument that an interplanetary zero point shouldn’t be tied to any one planet’s history at all. It’s a deeper question than it first appears, and I want to come back to it before the series ends.
6. Plan for the rollover before you ship. An integer that only grows eventually runs out of bits. That’s not hypothetical: it’s the 2038 problem sitting in every 32-bit
time_t. A time system meant to outlive its designers has to use a counter wide enough that it won’t overflow on any timescale anyone will live through, plus a clear migration path for when the assumptions break anyway. Thinking ahead is part of the design, not a patch you bolt on later.7. Relativity is not optional, so plan for the gravity well. There is no single universal tick rate. There is no now, and there is no master clock either. How fast a clock runs depends on how deep it sits in a gravity well and how fast it’s moving, so two clocks on two different bodies will never agree on raw elapsed time. The coordination layer doesn’t erase that. It manages it. Every location keeps its own proper time and converts to the shared reference through a known relativistic offset. GPS already does this at 38 microseconds a day; the Moon will do it at 58. The shared timescale isn’t a clock anyone physically holds. It’s a convention everyone translates into and out of, and the deeper the gravity well, the larger the correction.
Putting the pillars together, we get the shape of a system. The core of the idea is this: make it easy for humans, precise for machines.
We’re already building it
That architecture, one clean coordinate timescale plus a thin local display layer, is exactly what the metrologists have been inching Earth toward for years. It’s what abolishing the leap second is for. It’s what “civil time is a coordinate, not a description of the sky” actually means. It’s the thing every reformer in yesterday’s post was reaching for and couldn’t get adopted.
And it’s not hypothetical. Coordinated Lunar Time is being built as exactly this: an atomic timescale, relativistic corrections applied at the surface, mathematically traceable back to UTC, with a thin local display on top. The coordinate machinery already exists. The civil layer is the only genuinely new part, and it’s deliberately thin.
We’ve spent the whole series watching Earth refuse to make that separation, because the current arrangement is old and familiar and changing it has no immediate individual payoff. Going off-world doesn’t introduce a new problem. It removes the excuse. You cannot run a Moon base on leap-second-corrected, sun-anchored, time-zone-laden Earth time. The system breaks the instant you leave the surface, and we are about to leave the surface, in numbers, on a timeline shorter than most people realize.
The clock an interplanetary civilization needs is the clock we should probably already be using. The off-Earth deadline is just the thing that finally forces our hand.
Tomorrow I want to pull all of this together. Twenty-eight days of small, separate-looking problems: leap seconds, time zones, calendars, DST, relativity, leaving Earth. Tomorrow, the shape of all of them at once.
Sources
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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 26: The Astronomical Anchor Problem
If Einstein’s gift to us yesterday was that there is no universal “now,” today I want to come back down to Earth and revisit something more practical: how we measure time, and how we define the second.
We dug into the second itself back on Day 8. The short version is that there are two competing definitions, one astronomical and one atomic, and since 1972 they’ve drifted about 37 seconds apart. The gap is small, but it grows, and the system we built to manage it (leap seconds) is being dismantled. Today I want to look at what that means, and whether we should replace it with anything.
As you read this, I want you to sit with one question: what is civil time actually for? This isn’t a technical problem, it’s a values problem. What we anchor civil time to depends entirely on what we decide it’s for, and our civilization has only recently started changing its mind about that, mostly without noticing. More people should be paying attention.
Two definitions of the second
There are two ways to define a second.
The first is astronomical. A day is one rotation of the Earth, a second is 1/86,400 of that, and you divide the sun-up-sun-down cycle into uniform pieces. This is UT1, the modern name for “time measured by Earth’s rotation.” It’s what humans used for most of history.
The second is atomic. Since 1967 the official second has been 9,192,631,770 transitions between two energy levels of cesium-133 (we covered this on Day 8). This is TAI, International Atomic Time, and it’s defined without any reference to the Earth at all.
We know the Earth is a bad clock. Its rotation slows over geologic time, wobbles with the atmosphere and oceans, and drifts unpredictably on decade scales for reasons involving the molten core that we don’t fully understand. The astronomical second is not the same length from one day to the next.
The atomic second is, by construction, exactly the same length. It’s the most precisely defined quantity in human civilization, and it does not care what the Earth is doing.
So the atomic second became the official one, and UT1 has been drifting against it ever since. We invented UTC, the civil time on your phone, as a compromise: tick at the atomic rate, but insert a leap second whenever the gap from UT1 approaches 0.9 seconds. I wrote about the mess that caused on Day 19 and Day 20.
In 2035, leap seconds are being abolished… probably. After that, UTC will be allowed to drift from solar time by somewhere between one minute and one hour, to be decided by a 2026 vote. The astronomical anchor is being loosened, and maybe eventually cut entirely.
What “anchored to the sun” actually means
Civil time should be anchored to Earth’s rotation means two completely different things depending on who says it.
If a chronobiologist says it, they mean morning light should arrive at roughly the clock time when people wake up. That’s a circadian-health argument, the mechanism is real, and I dug into it on Day 21. But it’s an easy bar to clear: civil time only has to stay within about an hour of the sun. We already break that constantly. Time zones and daylight saving routinely shove the clock an hour or more off solar noon and mess with everyone’s circadian rhythm far more than a slow drift ever would, and society carries on. If anything, that’s a better argument that DST is dumb than that the anchor matters.
If an astronomer says it, they mean something more literal. Picture the Earth as a spinning sphere: at any instant you can calculate its orientation relative to the sun, and for most of history that was time. The official clock pointed at the Earth’s angular position because that’s all “time” ever meant. It’s a clean, logical definition, and it made complete sense for thousands of years. But it’s a definitional and cultural argument, not a biological one, and where the chronobiologist’s bar is easy to clear, this one is strict and expensive. With atomic clocks keeping time and UT1 tracking the Earth separately, anchoring civil time to that geometry makes far less sense now than it did at the dawn of civilization.
The metrologists' argument is that we can drop the astronomical anchor without losing anything humans actually depend on. We’ve all grown used to solar noon being noon, and that attachment is understandable, but in their view it’s swappable: let it go and you still have a stable, well-defined, engineering-grade measurement of time.
I don’t think they’re crazy. The tradeoff is real: we accept that civil time slowly comes unmoored from its position in the sky, and in exchange we get a clock that never needs correcting.
What is not decided yet
There are decisions still on the table. The 2022 vote killed the 0.9-second tolerance by 2035 but left the replacement open. After three years of the standards bodies working through options, the call lands this October: the 28th meeting of the CGPM, the General Conference on Weights and Measures, convenes in Versailles, France, and one item on the table is the new limit, how far UTC will be allowed to drift from solar time. The candidates range from keeping it nearly as tight as today to abandoning the anchor completely:
- 1 minute (no correction needed for about a century)
- 1 hour (a correction roughly every several thousand years)
- No limit at all (let civil time drift from the sun forever)
There is no neutral position here. The choice is really a vote on how much we still care about the sun.
Either way, astronomers lose the easy version of this. Today UTC doesn’t stray much from Earth’s rotation, close enough to read orientation straight off the civil clock. Once the tolerance loosens to a minute or more, that stops being true under every option on the table, so we will have to wire up UT1 directly to its own time signal.
The clock keeps clocking
Future generations will probably look back and ask why we did it this way. The honest answer is that time is complicated. Leap seconds made sense for part of our history, and they probably don’t make sense forever. The clocks will keep clocking either way.
Tomorrow: a survey of the prior attempts at fixing civil time. It has happened before, and we can learn a lot from how they failed.
Sources
- Atomic vs. Astronomical Time (TAI & UT1): International Earth Rotation and Reference Systems Service (IERS) and BIPM definitions.
- The Abolition of the Leap Second: Resolution 4 of the 27th General Conference on Weights and Measures (CGPM), 2022.
- Who is deciding the new tolerance: The CCTF Task Group on a continuous UTC, established by the BIPM in 2023 to draft the new maximum UT1−UTC value for the 28th CGPM (2026).
- Where it gets decided: The 28th General Conference on Weights and Measures, Versailles, 13–15 October 2026 — the meeting set to vote on the new maximum UT1−UTC value.
- The one-minute proposal: Levine, Tavella & Milton, “Towards a consensus on a continuous Coordinated Universal Time,” Metrologia, 2022 — argues a tolerance of about one minute keeps UTC within UT1 for roughly a century.
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Day 20: The Leap Second Is No More, Huzzah!
I know yesterday’s post was a real cliffhanger. Talking about leap seconds. I hate to burst your bubble, but today there’s going to be more of that when we cover the exciting and well-documented, internationally renowned meeting in November 2022.
I’m sure everyone totally knows about the General Conference on Weights and Measures (CGPM). Well, it turns out they have an important role as the world’s final authority on the metric system since 1875, a big deal. On that 18th in November 2022, they passed Resolution 4. It did one thing:
By or before 2035, the maximum value of the difference (UT1 − UTC) will be increased.
That means: we are abolishing the leap second.
This is a big deal. The leap second has been a feature of civil time for fifty years. Getting rid of it is the biggest change to “what time is it” since UTC itself got adopted in 1972. And it took almost twenty years of “discussion” to get there.
That “battle” is what today’s post is about. What got won and what got lost is way more interesting than the resolution text.
Two tribes, two ideas of “right”
Here’s the thing nobody tells you. There are two whole tribes of people whose job it is to care about what time it is. And they want completely different things.
Team Metrologists care about precision. Stability. The boring stuff. Their crowd is physics experiments, GPS satellites, financial exchanges, telecom networks, cloud data centers. To them, time is a standard of unit and measurement, like the kilogram or the meter. A measurement standard that inserts a random extra second is not a measurement standard. You’d never tolerate a gram that occasionally weighed an extra gram.
Team Astronomers care about Earth’s rotation. We should be on team astronomers every day, all the time. Their crowd is observatories, and the very old ideas that the day should obey man. To them, civil time should mean solar time. To them, UTC was a deliberate compromise. Atomic precision for the other team, plus a periodic correction so “noon” stayed put near the sun. Take away the correction and you’ve broken a contract that Noon is always in the middle of the day and midnight is always solar midnight. The fear is that the sun might rise at midnight at some point in the future.
Both are defensible? You can imagine serious people talking about serious things for decades at a time.
Well, guess what, the metrologists won, for now.
What actually moved the needle
The first real push to abolish the leap second came at the ITU-R (the radio-spectrum arm of the International Telecommunication Union) in 2004. The US, Japan, France, and Italy were the early supporters. The UK, China, and Russia opposed. The vote was delayed. And then delayed again. And then delayed again. Through 2012, 2015, 2019, the ITU-R kept punting because nobody could agree.
What actually changed the politics were the outages.
The 2012 Linux kernel meltdown that took Reddit, LinkedIn, and Qantas offline was the first global-scale “oh no this is real” moment. Then 2015 was quiet (smearing was working). Then 2016/2017 was Cloudflare. Then we had a long stretch with no leap seconds at all, the Earth started speeding up, and metrologists started seriously talking about the negative leap second. Nobody thought this was a good idea.
The fight stopped being “two professions disagreeing” and started being “metrologists vs a problem that might kill somebody.”
The vote got moved to the CGPM, a higher-status body than the ITU-R, sitting under the BIPM in Paris. In November 2022, in a single afternoon, the resolution passed.
The vote did not specify how leap seconds would be abolished. It just said the threshold would be increased, meaning UTC will be allowed to drift further from UT1 than the current 0.9-second limit, and that the new threshold would be decided by or before 2035.
The question that is up for discussion this year at the 28th CGPM in 2026 is: how much drift do we put up with before we have to do something about it?
Options on the table:
- One minute. UTC drifts from solar time by up to a minute, which takes roughly 100 years at current rates. Then we insert a “leap minute” once, in some coordinated worldwide event. Still sounds dangerous.
- 256 seconds. A computing-friendly number (it fits in an 8-bit field). Drift accumulates over ~400 years.
- One hour. Roughly 5,000 years out. By that point the leap is just “everybody shift one time zone for a few years until civil time re-syncs.”
- No threshold at all. Let UTC and UT1 diverge forever. Civil time eventually has nothing to do with the sun. The option astronomers hate most, and engineers find most tempting.
This is genuinely undecided. The drafting task force is still working on it. The 2026 vote will probably set the threshold, but the mechanism (how an eventual leap minute or hour actually gets inserted, how it’s announced, how software handles it) is still an open problem.
What happens when (or did they) metrologists win
The biggest immediate win is that POSIX becomes correct.
Quick recall from Day 13: Unix time is defined as “seconds since 1970-01-01 UTC,” with the deeply weird caveat that it pretends leap seconds don’t exist.
So now every day is exactly 86,400 seconds, full stop. This made Unix time a lie for decades. A lie that all of computing depends on.
By killing the leap second, the lie becomes the truth. UTC will, after 2035, actually tick uniformly.
POSIX’s definition starts being an honest description of what’s happening. Every piece of date-arithmetic code ever written that assumed
86400 * daysequals a stretch of days will be correct.It’s maybe a boring victory, if it’s just the absence of a problem. In 2035, time finally heals.
What astronomers lost
The astronomers, the people who built the leap-second system in 1972, lost a principle. A simple and very old one: noon should be when the sun is overhead. Midnight should be the middle of the night. That contract is older than civilization, and UTC was the deal that kept it intact through the atomic age.
Abolishing the leap second breaks that contract. Slowly. Over centuries. But permanently. Their fear is that eventually, not tomorrow, not in 100 years, but someday, the sun will rise at midnight.
Here’s what’s not lost. The astronomers' toolkit for actually measuring where the Earth is is excellent and getting better. They watch distant quasars with radio telescopes spread across continents and know where the Earth is to the millisecond. They’ll still know exactly when solar noon happens. They’ll just have to broadcast that signal themselves, almost certainly a UT1 service separate from UTC, instead of getting it baked into civil time.
What gets lost is the default. After 2035, civilization no longer says with “noon-is-noon” as a built-in promise. If you want it, it’s there, you just have to opt in.
So what’s the big deal?
The disagreement is just about time.
If civil time is a measurement standard: you optimize for precision and stability and you remove the ambiguity. The metrologists' answer is correct.
If civil time is a human social agreement about when noon is: you accept a little time wiggle, every now and then and who isn’t a fan of a little wiggle, in exchange for keeping noon attached to the sun. Well then, the astronomers' answer is correct.
I can see how both answers are answers, but I think they are answers to different things.
Computers and the people who use them.
For systems, all our ways of tracking time, the metrologists are correct. End of story. All the GPS satellites, financial exchanges, telecom networks, cloud data centers need a clock that just ticks; uniformity, no surprises, no funny business. This is something the 2022 vote got correct.
But what is Civil time if its' not for the people? And maybe there’s still a way for everybody to win. Keep the systems on uniform atomic time, no discontinuities, no outages, and let civil time keep its old promise. Noon stays near the sun. Even if we have to do something clever every century to make it work. A leap minute. A coordinated time-zone shift. Whatever it takes.
The systems fight are over but boy do we got some stuff to figure out with that civil time.
Tomorrow we get into the real mud, the dirt of it. What everyone hates….
The case against daylight saving time.
Sources
- Resolutions of the 27th CGPM (2022) — BIPM. The official text of Resolution 4, which increases the tolerance for UT1-UTC and effectively abolishes the leap second by 2035.
- The End of the Leap Second — Nature (2022). Comprehensive coverage of the historic vote at Versailles and the twenty-year debate between metrologists and astronomers.
- Abolishing the Leap Second — The New York Times (2022). Explains the tension between the ITU-R, the CGPM, and the risks of the negative leap second.
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Day 16: How the World Agreed on a Date Format (Except the US)
There is a war that has been quietly raging for about a century, and it is fought over six little characters.
05/06/26In the United States, that is May 6, 2026. In most of Europe, it is June 5, 2026. In Japan, which uses a year-month-day order and frequently uses the imperial calendar, the
05might be read as year 5 of the Reiwa era (2023). In Iran, the entire premise is wrong, because Iran’s official calendar is the Solar Hijri and the current year is 1405.So here we are. A date written by one person and parsed by another is, in the general case, an act of faith.
The most consequential standards effort of the late 20th century was an attempt to end this. It succeeded, sort of. The format it produced,
2026-06-08T14:30:00Z, looks unremarkable now, but it represents a multi-decade campaign to drag the world’s date conventions into a single, unambiguous, machine-parseable shape.That standard is ISO 8601, and the story of how it won is the story of why your API logs look the way they do.
What’s actually wrong with
05/06/26Let me give you the tick of the tock (lay of the land). Every culture has a different intuition about which number comes first in a date, and none of them is wrong.
In the United States, the convention is month-day-year. This descends from spoken American English, “May sixth, twenty-twenty-six,” where the month comes first in speech.
In most of Europe, Latin America, and much of Asia, the convention is day-month-year. “The fifth of June, twenty-twenty-six.” The day is the first specific element.
In East Asia, the convention is year-month-day, written largest-unit-first. This reflects a linguistic preference for going general-to-specific that runs the opposite direction of the English phrasing.
Who is to say which is more correct than another? The problem is that a single string of digits separated by slashes can mean three different things depending on who wrote it, and there is no way other way to tell.
When the ambiguity bites
It’s not just an annoyance.
International travel figured this out the hard way. Across global passport documentation, the convention settled on a three-letter month abbreviation:
08 JUN 2026. It’s unambiguous because no month is named06. The international passport standard (ICAO Doc 9303) mandatesJANthroughDECfor exactly this purpose.In healthcare, patient safety organizations have flagged date ambiguity as a documented source of medication error: a chart that says
7/8/09can be read as July 8 by one clinician and August 7 by another.The shape of the problem is the same across medicine, aviation, logistics, contracts, and customs declarations. Different conventions lead to confusion and errors.
The standard
In 1988, ISO published
ISO 8601:1988. Pick one format, make it unambiguous, make it sort lexicographically, make it machine-parseable, and standardize the world on it.The format they picked:
2026-06-08T14:30:00ZThe choice of
YYYY-MM-DDwas deliberate. Year-month-day is the East Asian convention, but it has a technical property that the other two don’t: it sorts correctly as a string.2025-12-31comes before2026-01-01whether you sort by character or by number.12/31/25and01/01/26do not. For the emerging computing industry of the late 1980s, databases, log files, file systems, this was a decisive advantage.The capital
Tseparates the date from the time. Not pretty, but unambiguous. The trailingZ(informally pronounced “Zulu”) means UTC. This timestamp has no timezone offset, it is anchored directly to UTC.What actually use: RFC 3339
ISO 8601 is too permissive for engineering use.
It allows fractional seconds. It allows omitting components. It allows the basic form (
20260608T143000Z) without separators. It allows week dates and ordinal dates. It allows24:00:00as midnight (this was removed in 2019, then reinstated by amendment, in one of those standards-committee compromises that satisfies no one).So in 2002, the IETF published
RFC 3339. RFC 3339 is a profile of ISO 8601, a strict subset that picks one form and forbids the rest. The basic form is disallowed. Week dates are disallowed. The time component is mandatory. The timezone designator is mandatory.This is what every modern internet API actually uses. GitHub, AWS, Stripe, Cloudflare, OpenAI. They accept RFC 3339, not full ISO 8601. They reject
20260608T143000Zeven though it’s legal ISO 8601.What everyone calls “ISO 8601” in casual conversation is, almost always, RFC 3339.
What ISO 8601 isn’t
A few things worth being clear about:
- ISO 8601 is not UTC. UTC is a timescale. ISO 8601 is a format.
- ISO 8601 is not Unix time. Unix time is the integer
1781055000. ISO 8601 is the string2026-06-08T14:30:00Z. They can represent the same instant. They are not the same thing. - ISO 8601 does not solve leap seconds. The format permits
:60in the seconds field, but what to do with such a value is implementation-defined. - ISO 8601 does not include the calendar system. It assumes the Gregorian calendar. No provision for Islamic, Hebrew, or Buddhist calendars.
The civilizational payoff
There is a sense in which
2026-06-08T14:30:00Zis the most consequential string format in modern computing.While legacy systems still cling to their own formats—HTTP headers use RFC 1123, Git and JWTs use integer Unix timestamps, and X.509 certificates use ASN.1—RFC 3339 has conquered the modern web. It is the default serialization for datetime objects in modern programming languages. It appears in the JSON payloads of almost every modern API (GitHub, Stripe, AWS, OpenAI). It is the standard format for XML’s
xs:dateTime. It is written into millions of cloud infrastructure log lines every second.It is the closest thing modern technical infrastructure has to a universal vocabulary for the question “when did this happen?"
It won because it was unambiguous and sortable, and a single committee was willing to pick one of three equally valid cultural conventions and tell the other two cultures to deal with it. Most international standards die in the negotiation. ISO 8601 survived because the technical advantages of
YYYY-MM-DDwere strong enough to overwhelm the political cost.Us Americans haven’t adopted it (yet). We still write
06/08/2026on bank checks, forms and filings, but the machines we all use are on 8601 and they are doing most of the talking.
Sources
- Japanese era name — Wikipedia — Reiwa began 1 May 2019; Reiwa 5 = 2023.
- Solar Hijri calendar — Wikipedia — year 1405 began 21 March 2026, ends 21 March 2027.
- ISO 8601 — Wikipedia — first published 1988; ISO 8601-1:2019 removed
24:00; the 2022 amendment reinstated it. - ISO 8601-1:2019/Amd 1:2022 — the amendment that put
24:00:00back. - RFC 3339 — Date and Time on the Internet: Timestamps — IETF, July 2002. Profile of ISO 8601 used by most modern APIs.
- RFC 3339 vs ISO 8601 — visual map of which forms each standard accepts; basic form (
20260608T143000Z) is valid ISO 8601 but not RFC 3339. - Machine-readable passport (ICAO Doc 9303) — Wikipedia — ICAO standard requiring three-letter month abbreviations (
DD MMM YYYY) in the visual inspection zone of all passports. - ISMP List of Error-Prone Abbreviations — highlights the risk of ambiguous documentation and dates in medical records.
- RFC 1123 — Requirements for Internet Hosts — specifies the required date format for HTTP Date headers.
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Tomorrow: Unix time, the second-counting system that runs under every timestamp you’ve ever seen, and the rollover problem that hits in 2038.
Programming Software development 30daysoftime Standards Iso8601