The only better thing is the organization being called "International Earth Rotation Service"

For many years, the title of the leadership role over the various precise time products at the USNO was "Director of the Directorate of Time"

Sounds like something out of a Douglas Adams novel.

They should call themselves Time Lords

Planetary Defense Officer [1]

[1] https://en.wikipedia.org/wiki/Planetary_Defense_Coordination...

"Director Earth Orientation Center of IERS Observatoire de Paris, France"

Even the titles are sci-fi.

In short, yes, the weather, geology, and signicantly, human movement of water via aquifer draining and dam building, as well as glaicial and ice melts, all contribute to unpredictable changes in the earths rotational period, as well as the axis of rotation. The models for this are IIRC trigonometric polynomials of fairly low order, so even if we could model the unpredictability perfectly, truncation error would limit our ability to distribute the model at super high accuracy. The existing models are built in to, eg, satellites, so you can't just make them arbitrarily complex.

Fun fact: leap seconds will stop being a thing soonish. I think they phase out in 2035, with a delay because Russia needed time to update glonass satellites.

(Note: on mobile, this is from memory, details need checking ;))

Yes, all of those and more. Our measurement precision is much better than the year-to-year first and second derivatives of day length. https://datacenter.iers.org/singlePlot.php?plotname=Bulletin... has the most relevant plot to this; the vertical jumps reflect leap seconds. (IERS has other plots for other dimensions of rotation, but I like this one.)

Since I was checking the Wikipedia article anyway (for when the last leap second was inserted), it also has an answer for this:

"Because the Earth's rotational speed varies in response to climatic and geological events, UTC leap seconds are irregularly spaced and not precisely predictable."

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

Yes. Geological activity, movement in the outer core, atmosphere, oceanic currents, melting ice, earthquakes, to name a few.

Earths rotation has been unusually fast lately. So there is not enough drift to warrant a leap second.

I like the argument that we should have 12 months that are exactly 30 days long, and then merge whatever is left into a single timeless holiday.

Lol the Kernel is "easy" it's userspace and distributed systems that are a b*tch

Lol. Exactly!

The problem is future societies harvesting the engines for interstellar probes. This problem has been discussed in a series of books by Larry Niven.

No, jet engines push against the atmosphere and the atmosphere is a part of the earth

It would appear that this has worked as they haven't had to insert leap seconds for quite a while.

I feel like we can all just jump at the same time. I mean, we only need a second or two, right?

Wouldn't it just be easier to have Superman fly around the planet a bunch of times really fast to do the same thing? Then you wouldn't have to worry about having to deal with all of that engine maintenance.

Leap days, February 29th, are not at the level of time zones. Different time zones do not disagree as to when March 1st will occurs immediately after February 28th.

The changes in Earth's rotational speed that leap seconds help account for affect the whole globe. Why shouldn't the effects be noted in the global time standard?

god that would be awful. Can you imagine time zones being one second off from each other. Or two or three? ah yes, india is GMT+4:30:03, where europe is GMT+0:59:58

> This means the atomic clock is behind the solar clock by 37 seconds?

If anything, it's the other way around.

A UTC day is defined as exactly 86400 SI seconds. But an actual mean solar day is a few milliseconds longer (although the difference is not constant due to irregularities in the Earth's rotation--but the average difference is expected to slowly increase over time). SI seconds are counted by atomic clocks, so UTC advances its day by one every 86400 atomic clock seconds.

But a solar clock that advances its day by one every time the mean sun reaches noon (it has to be the mean sun because the rate at which the actual sun moves across the sky varies over the course of a year, we need to look at the average) will advance its day a few milliseconds later than UTC does. Or, to put it another way, each time period that the solar clock says is exactly 86400 seconds, is a few milliseconds longer according to the atomic clock.

As this happens day after day, the difference accumulates, and when it gets close to being a full second, a leap second gets inserted into UTC, so that one of its days is 86401 seconds long instead of 86400. The reason for this is that UTC is not just counting atomic clock time; it also has to stay in sync with where the sun is in the sky since so many human activities are tied to that. And we humans have defined "in sync with the sun" to be "within a second of the average sun". In other words, we want UTC noon to be within a second of mean solar noon on the prime meridian.

So the 37 seconds is how far mean solar noon would be behind UTC noon, if we didn't use leap seconds--at UTC noon, the mean sun would be 37 seconds short of actually crossing the prime meridian in the sky.

Apparently December 2016 was the last time a leap second was inserted, at least that's what Wikipedia says:

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

> I also don’t understand the reference to 2017.

My guess is that is when they last changed the offset, so the -37s has been in effect since then.

It’s a huge problem. The most common approach to address it is called smearing; the duration of each second for a 24 hour period ahead of the “leap” is adjusted. For strict ordering systems this works as each device maintains time sync with the global clock, the duration of a clock cycle is just slightly different. I think this was in the original Spanner paper, actually.

Some rare systems use monotonic oscillator seconds and ignore the earth rotation second, but if you ever have to translate those to real time, you get an accumulating disaster over time and it’s generally regarded as not a good idea.

Leap seconds are not added on a regular schedule like leap days, they depend on physical measurements of Earth. So high reliability systems with comprehensive timekeeping would not be perturbed by these choices, I would think.

Probably from the "Content-Language: de" header

It's a mix of french and english... so it's german.

Not anymore forever. We’re just not adding one for this year. We might need one next year, we might not. It all depends on the Earth’s rotation and orbit

There's an opportunity to insert or remove a leap second twice a year. They only decide about 6 months in advance of each opportunity what to do (leap second, skipped second, or do nothing).

really, my I just don't have the time to keep up with this.