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Comment by neutrinobro | Hacker News Reader

Yay! No more leap seconds to manage! This is going to make my life much easier.

Edit...scratch that, now I have to keep track of UT1-UTC as a separately continuously varying parameter provided by IERS instead of tzdata

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It shifts the problem elsewhere, though as you suggest it's sometimes still the same people having to deal with it! For example, anyone relying on celestial navigation who had until now been satisfied with up to 1 second of time error is going to need to start keeping track of UT1-UTC before it starts exceeding those old bounds. This will be possibly within a few years, whenever the next leap second would have been inserted/removed.

A chronometer off by one second gives an approximate error of 0.25 nautical miles at the equator. Meanwhile the general precision of celestial navigation is 1-5 nautical miles. If you need high level accurate positioning, celestial navigation is already not an option.

In the open seas, celestial navigation is more than accurate enough. Once you are closer to shore, where the greater precision is needed, better options exists. Lights, ranges, radar, visual, etc.

What do you work on that requires you to care about UT1? Something astronomy-related?

Didn’t Julia choose UT1 for their standard date time library? Although they might want to reconsider with this decision

Julia is not actually doing anything unusual here. When their documentation talks about UT1, this is just a fancy/confusing way of saying that their datetime library isn't aware of leap seconds, just like every other mainstream programming language AFAIK. The abolition of future leap seconds will only reduce the number of weird edge cases this generates, which is all to the good. I suppose they'll need to change the docs, though.

The clocks we have all basically work in TAI. Historically UTC is TAI plus occasionally a bodge (the leap second) to move it closer to UT1 when it's wrong by too much.

Nobody has a real UT1 clock†, some observation sites prepare guesses at UT1 mostly in terms of how far it deviates from TAI because you can just buy clocks that keep TAI really well.

† You could say this damp rock, "The Earth" is such a clock, and I guess I reluctantly accept that argument but then OK the UI for that clock is abysmal, nobody can use this the way you'd use an actual clock unless they accept miserably bad precision.

The Earth makes for a terribly imprecise clock, but it is the UT1 clock, or rather its defining component.

The UI is a ring laser gyroscope, right?

I’d say most ‘mainstream’ libraries pretend that every day, even a day with leap seconds, has 86400 regular-length seconds. But I thought that within UT1 the length of a second varies every day, so I would not have called that UT1.

Somewhat the inverse, geodesy.

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