Hacker News Reader

Your article is about time zones, not leap seconds?

The US has put forth a proposal to abolish leap seconds. It is now supported by China, Australia, Japan, and South Korea. The ITU keeps punting on actually voting on it - it's now scheduled for 2023.

https://en.wikipedia.org/wiki/Leap_second

A day already drifts... every single day in fact. Why is 0.9 sec the magic threshold for maximum drift? Why can't it be 1 minute of drift, or 1 hour of drift? We are putting out problematic corrections for something a minor drift on the scale of years that should be happening on the scale of centuries or millennia in my opinion.

That's interesting, I stand corrected. TIL that it's actually a heavily disputed topic and much less clear than I painted it, I had quite a different impression before — thanks!

Happy to see it is not just me that enjoy getting rid of my ignorance : )

It's a lot easier to test and prepare for something that occurs at least semi-regularly than a monumental event far into the future that is "so far into the future we don't have to worry about it"....

If we abolish leap seconds (and any other changes to UTC) and let the error accumulate until it hits 30 minutes then a 1-hour time zone change can adjust for it. Time zone changes happen at least semi-regularly so it wouldn't be monumental.

Wouldn’t that move the international date line?

I guess so, but I don't know why that matters.

The international date line isn't straight in order to avoid land. Moving it would be problematic.

think of it as ordinal: you're shifting left 1 unit, not moving the line, per se.

Still matters because some places want to make sure it's the same day (according to their local reckoning) as it is somewhere else in particular (usually a major trading partner).

Or the next town over.

The other boundaries are a lot straighter.

Imagine what would happen when the International Date Line ends up in the middle of the US.

It would take millennia for such an error to accumulate. Leap seconds are inserted less than once a year and 30 minutes is 1800 seconds.

Falsehoods programmers believe about leap seconds: 1. The rate at which leap seconds are inserted will remain roughly constant. [...]

The Earth's rotation is slowing down (by about 2 ms per day per century), so the difference between TAI and UT1 is increasing quadratically, not linearly.

1 minute of drift seems fine. 1 hour of drift is rather noticeable.

If the drift is about 0.5 second per year, about a minute of drift will have to be compensated on a century border.

The third principle of Continuous Delivery is "If something is difficult or painful, do it more often".

So, if leapseconds are actually painful for you, then maybe we need to contemplate making this kind of adjustment on a finer timescale, like milliseconds.

OTOH, if you think leapseconds are painful now, just you wait until you postpone this pain and do it even less frequently.

>The third principle of Continuous Delivery is "If something is difficult or painful, do it more often".

That only works assuming you need to do it at all.

If leap seconds are useless (to the majority of users) or insufficient, not doing them is preferable to doing them constantly.

> So, if leapseconds are actually painful for you, then maybe we need to contemplate making this kind of adjustment on a finer timescale, like milliseconds.

That is what a lot of organizations do, "smearing" the leap second since they know their systems can't handle the discontinuity. I think this shows that software has failed in general at handling leap seconds correctly. As another said, I think leap seconds are unnecessary complexity with the frequency at which they happen.

On the contrary, I think that the smearing behavior is an indication that leap seconds poison an otherwise-useful model of reality. The discontinuity is an annoying edge case driven by the fact that "time error" accumulates, so it seems to me that that a 1-day smear is a more natural approximation than an instantaneous discontinuity. That, and tuned for the attention span of human organizations.

That principle is more of a koan than actual concrete advice.

For example, deleting your entire codebase and firing all your developers is painful, but even the most continuous deliverer wouldn't advise you to do that more often.

Do you also pee in front "wet floor" signs?

Getting past pedantry, the advice is obviously about foreseeable, repeating parts of normal business, and it applies to more than devops.

A long time ago (tail end of the "desktop publishing revolution"), I was a production assistant, and then manager at a magazine. We published six times a year. Towards the end of my first year there, I realized we had the same problems, right down to our Advertising Director's emotional meltdown, every. single. issue.

After getting to know folks working at other magazines and people at our press, I noticed that the monthlies seemed to run smoother with less drama, and the weeklies were even better at it. Eventually I realized it was because they had to be. If there was some minimum amount of human drama that had to happen, it was forced into exhibitions that didn't disrupt the (tight) schedules. If last-minute changes from flakey advertisers came in, they didn't cause a firedrill, they just didn't run, because that issue is already on the press and we're talking about the issue after next now. And so on.

The general principle is actually very straightforward, and applicable all over the place, including your personal life. If you have high-friction processes, devoting time and attention to them is the way you make them lower-friction processes. And while it may be possible to do that without doing things over and over until you get there, it probably is not possible for you to get there without repetition, else you'd not have the problem in the first place.

Doesn't every company do this slowly as they replace code and developers?

The obvious correction is to change the duration of a second such that a year is exactly $integer seconds long. While this will make the duration of second drift from year to year, that drift is so small that everyday devices like consumer-grade computers could just ignore it, provided they're NTP synced once every five years or so. Physicists can just keep using whatever they're using and call it by a different name. Ideal solution all-around.

The core issue is that the number of days per year is messy, so it's not possible to have a 'nice' number of seconds in a day and also in a year.

The best solution is probably just to use a nice number of seconds per day and accept the fact that in 100ish years summer will start in March, not December. It's not like we need to build our entire society around planting and harvest any more.

That's not anywhere close to "the best solution"

This discussion isn't going to be very meaningful unless you wanna tell us what 'best' means to you.

That's fair. I simply can't see the best solution relying on getting rid of deeply ingrained culutural norms that span thousands of years.

Yeah, I can see that being an issue, at least until a decent proportion of humanity lives off-world. I can't see people living in the asteroid belts adding arbitrary leap-seconds.

Of course, once you start dealing with astronomical distances and speeds, the whole concept of a single universal measure of time kind of goes out the window anyway so it's probably going to get worse, not better. :P

(FWIW my definition of 'best' here is something along the lines of 'simple, no special rules or tinkering, gets translated to a human-readable local time on demand'. Which is pretty much how Unix epoch works, come to think of it.)

Yes... let's let future asteroid dwellers solve their own problems, which will be as much cultural as technical. Today's elegant universal solution is sometimes tomorrow's Esperanto: perfectly useless.

March is already summer here (Southern Hemisphere). We have all sorts of weird eccentricities due to "cultural norms" (we use snowflakes on our Christmas cards in mid-summer, whereas the Steam Summer Sale happens mid-winter).

Not to mention with climate change, we're probably going to have to deal with many other changes in season etc. anyway.

All of us deal with the fact that the day gets shorter and longer every year anyway (and daylight savings didn't seem to be a terribly good solution).

I think having the seasons slowly drift is a non-issue, provided it's just slow enough to not be noticeable from year to year.

Are we to infer that your lack of criteria for "best" in your own post means that it too is meaningless? You made a breath-taking leap going from {our society isn't as dependent on planting and harvesting anymore} to {therefore it's "probably best" to radically alter universal concepts of temporality to partially solve an obscure technical problem}. Methinks the burden on proof lies firmly in your court on this one.

I'm not the one arguing with a statement in that post.

But we do build our entire society around sports seasons.

That third principle is about facing (and implicitly, automating) your difficult-but-necessary processes. Outside of that narrow scope it's terrible advice. Being in a car crash and converting a country from one system of units to another are both difficult and painful and you should do either as seldom as possible.

> Well, the problem with this is that every simplistic view at time is... well... too simple. It's not that many people haven't tried, I especially like this article: https://qntm.org/abolish

This has nothing to do with leap seconds. Leap seconds are the worst mechanism in keeping time, there's not a single advantage to having leap seconds.

> A day is defined as the rotation of the earth around its axis.

And we can now measure time with precision high enough that tying to Earth's rotation is not acceptable. We can still use timezones to fix the shift.

> Changing any of these will make the summer drift into the winter, or the night into the day, or whatever.

Yeah, and it will take a millennium for Earth rotation to shift enough for people to notice it. On the other hand, you'd have no problem with summer/winter time I presume?

> Yeah, and it will take a millennium for Earth rotation to shift enough for people to notice it. On the other hand, you'd have no problem with summer/winter time I presume?

No, I don't, as they are just views on a monotonically increasing time scale named UTC that keeps up with Earth's rotation, so that every single thing from climate diagrams to everything else humanity is syncing on keeps working and being comparable.

> We can still use timezones to fix the shift.

Or, we could not do that. Everyone is free to use TAI inside their own projects as they see fit if they have the needs for strictly monotonically increasing time. I would argue that leap second smearing has way less artifacts in practice than bolting time zones onto a shifting UTC time.

"Changing any of these will make the summer drift into the winter, or the night into the day, or whatever."

Leap days, sure.

Leap seconds - as the article points out, there have only been 27 so far since 1970. Less than a minute per century isn't much drift, and could be corrected in a bigger block later.

> A day is defined as the rotation of the earth around its axis.

When you get into the world of programming for most people, businesses especially, a day is defined as 24 hours. We like to think that our days and months and years are tied to vast astronomical forces, for romantic reasons, but when it comes down to it, everything comes back to the second, and the second is defined to be a single unvarying length of time.

Well, depends.

In TAI: A day is 24 hours (86400 seconds always), and a second is a SI second.

In UTC: A day is a rotation of the earth, and a second is a SI second. (And since these are incompatible, we have to introduce leap seconds).

In UT1: A day is a rotation of the earth, and a second is 1/86400 of a rotation of the earth.

Julia, interestingly, uses the UT1 notion, thus avoiding leap seconds, IIRC.

My point is this: Most people don't know about UTC/TAI/UT1 or any other standard. They know what's common knowledge, and what's common knowledge is that one day is 24 hours precisely, one hour is sixty minutes precisely, and one minute is sixty seconds precisely. Therefore, when writing software to interface with most people, including businesses with contracts defined in terms of those time definitions, one day is 24 hours or else you end up with problems.

That's why I advocate using UT1 in programming (like Julia), where all of the above is true. The cost we pay for that is that a UT1 second is not exactly a SI second, but I don't see how that matters except in GPS etc.

Well, just to nitpick, seconds do vary in comparative length from reference frame to reference frame...and that actually does start to matter in global computing.

Seconds don't vary, your approximation of a second varies.

If you want to nitpick, you're going to need to start with Cesium-133 oscillation periods as averaged from over nine billion samples.

I like the cut of your jib. But I suppose what I was saying was that, for the purposes of establishing “now”, “now” isn’t really standardizable except with respect to a single inertial frame, and any time-keeping that occurs outside of this inertial frame will not be absolutely in sync, even though it may have a highly accurate measure of time for its own inertial frame.

This matters when computers are bouncing records about time around satellites and across the global.

Edit: I have no idea what I’m talking about so please do not hesitate to correct me on the particulars!

Seconds do vary because there are no privileged reference frames in the universe. You'll get a different measurement if your cesium measuring experiment is traveling at a different speed than you are.

That's the direction of your mass-energy vector, not seconds.

A bit like complaining that UTC is wrong because it doesn't match your local Solar time.

The earth doesn't travel the same course each year. It's chaotic.

Best to define a second as a certain distance light travels in a vacuum and use that to build minutes, hours, etc. Then, have a fixed geo reference point (like, say, geo 0:0) that holds an atomic clock as a main reference.

We are only really talking about local coordinate changes in the time dimension, really, so might as well simplify.

> The earth doesn't travel the same course each year. It's chaotic.

I would prefer to call it quasiperiodic.

See Laskar's work, mentioned here: https://en.m.wikipedia.org/wiki/Stability_of_the_Solar_Syste...

There have been a net +27 leap seconds since the 1970’s. That’s not enough to turn summer into winter or day into night. That’s roughly a full minute per century.

Your statement is both true and misleading.

The speed of the Earth's rotation is slowing over time. Therefore leap seconds are becoming more and more common. In a century, we should be averaging something like 1 a year. In 500 years, we should be averaging one every few months. And so on.

It took over a thousand years for the Julian calendar to fall apart. Our current timekeeping system will also fall apart eventually, and I would be surprised if it lasted as long.

Even if there was a leap second every year... does it matter? It would still take several hundred years for the difference to be noticeable, at which point you can just change UTC by +-1h.

What it means is that the discrepancy between clocks and time of day is growing quadratically. It won't matter to us in our lifetimes. But eventually it will be a problem.

It will take on the order of a thousand years for the discrepancy to add up to an hour. In 5000 years, it will be around a day. The fact that it is currently growing about a minute per century is true, but not a good predictor of what will happen.

That said, I prefer if we just lose the astronomical basis for time keeping, and let our distant descendants figure out that they should use time zones, and not modify UTC. Hopefully by the time it becomes obvious that clocks are drifting too fast for time zones to change all of the time, we're a multi-planetary species and paying attention to what is happening on the Earth seems quaint.

In 5000 years the majority of humanity, assuming we haven’t gone extinct, will live in space and the astronomy will be moot anyway.

500 years from now, if we're still alive, enough of us will be living in space colonies rather than on the Earth's surface that the Earth's rotation will not necessarily be immediately relevant to everyone's lives.

Regardless, we've had maybe half a minute of drift since the 1970's. If the drift is 1 minute in the 2000's, 1 second per year in the 2100's, 2 seconds per year in the 2200's, 3 seconds per year in the 2300's, etc., then by 2500, the cumulative drift would add up to...60 + 100 + 200 + 300 + 400 + 500 or 1560 seconds of total cumulative drift by 2600. That's less than half an hour. If we didn't bother accounting for leap seconds, UTC midnight would be only half an hour off from astronomical midnight in 600 years, which is roughly the same error inherent in most time zones.

We need a pseudo day still due to our sleeping rhythms but perhaps people could choose that based on personal preference not just stick with 24h

The day would shift half an hour in the next 600 years. That’s half as much as it shifts twice a year for DST, except it would happen gradually over a period of time roughly equal to the time between the fall of the Eastern Roman Empire and today.

I was sort of nodding to the people who claim they have a 25 hour sleep cycle. Once we are in space and using artificial light, you can choose the sleep cycle that suits you. But predicting things in 500 year is just Sci Fi I guess!

I'm reasonably sure that any assumptions about how our anatomy will look like in 500 years are more wrong than right.

We should abolish local time too. There should be a single time for every country which is the number of milliseconds since either the beginning of human civilization, the beginning of earth or the universe.

A. Why?

B. If you want to be super strict about it, as I imagine you do, that scheme would hit problems with relativistic effects. Local time is the only real time.

I like Swatch Internet Time.

So You Want To Abolish Time Zones

https://qntm.org/abolish

Mean Julian Days (MJD) are the agreed standard for something like that. Abolishing local time has a number of issues as linked in other comments. The time standards we currently have are all well suited to their purpose, it's just a case of picking the most appropriate one for the task. (Plenty of room for more TAI in modern technology).

>A day is defined as the rotation of the earth around its axis.

>A year is defined as the rotation of the earth around the sun.

Sounds like we need a generic geo-solar measurement.

I know it will never happen because of cultural reasons, but really, we need to separate the time (as in how I describe a point on the time scale, for, let say, a meeting, especially one that involves people in globally distributed locations), and the cultural aspect (at what time people are sleeping or eating lunch).

Right now those two things are intertwined, and that's bad. Not everyone eats lunch around noon or go to bed at 23:00 anyway, so the cultural part is very fuzzy.

I should be able to describe time in an almost metric way. A unit that is the same no matter where I am in the world and doesn't change based on how fast a rock moves around a fireball. "Hey person in Japan, let's have a video meeting at 1,234,99" where that number means the same thing to the as it does to me. Its going to be dark for one of us and bright for another.

Then we can have a different unit, let's call it "day offset". That is the offset from the first number that dictates when a particular area considers to be "the day", when the average people wakes up, have lunch, have dinner, go to bed.

"Let's meet at 1,234,99. I know you're in Japan and your offset is +9,23 while here it's "-5,78" so it's a bit inconvenient, but hopefully you can make it!"

Yes, I realize I'm roughly describing how time and timezone works, with an important difference: with the current system, people live around the adjusted number. The number after the timezone is applied. After the leap seconds and all that crap is applied. Some people argue about daylight saving or no. Computers have to deal with all of it. Let's make the non-adjusted number what people use day to day, and the "offset" is a static number picked by the locals, that include stuff like daylight saving, leap seconds, and various other cultural adjustment. Its only purpose is to communicate the cultural or location difference between 2 people.

Obviously that will never happen, but Ill keep dreaming.

It's called UTC. You just want UTC with a different string format and a timezone format appended to it, or maybe seperate from it.

Pretty much, yes.

Swatch Internet Time:

https://en.wikipedia.org/wiki/Swatch_Internet_Time

And Julian day:

https://en.m.wikipedia.org/wiki/Julian_day