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Ask HN: Are systems ready for the first negative leap second?

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Re: Ask HN: Are systems ready for the first negative leap second?

#31

Post by chaps »

not-a-llm wrote: post #16
toast0 wrote: post #13

Earlier quoted context omitted.

The less brilliant thing about the smear is that if your ntpd syncs from smeared and unsmeared servers, the results aren't great. It would have been better if they would have kept the time on the wire accurate or added mandatory protocol stuff to avoid confusing things for ntpds configured to different leap second handling.

if you need below 1 millisecond time accuracy, probably you know what you are doing and you wont mix NTP servers (and I think you need PTP for that)

You'd think so. Legacy servers that've been running for ten years really puts a hitch in that.

Re: Ask HN: Are systems ready for the first negative leap second?

#32

Post by blaze33 »

netsharc wrote: post #20
dgrin91 wrote: post #14

I wonder how many systems actually care? I presume the core NTP servers handle this well, and most systems just feed off of that? GPS satellites probably handle it well too, but maybe some consumer or even industrial GPS receivers don't? Maybe some trading systems? I don't think crypto systems care too much.

I wonder if there's things that run 24/7 and need to be monitored.. e.g. if you have oil flowing through some pipeline at 100 liters/second, one particular minute will have 6100 liters, and someone will want to get paid for that 100 extra liters. But the meter/reporting tool would say "Well, we measure every second, and the meter reported a constant rate of 100 liter/second, and as we know we have 60 seconds in a min…

I once worked with smart meters for electricity consumption that do run 24/7. Leap seconds were not an issue but we had a very similar one now that I think about it: DST shenanigans!

Like how much time is there between 2 and 3 am? Usually one hour, but sometimes 2 and also sometimes 0. It looks simple at first but it creates a lot of edge cases that your business logic now needs to handle and we had a fairly complex system for this.

Re: Ask HN: Are systems ready for the first negative leap second?

#34

Post by dmurray »

subscribed wrote: post #6
d00d0ff000 wrote: post #2

NTP. By any other standard, most manually set clocks are up to a full minute off all the time.

Yeah, but we're thinking of systems where nanoseconds matter. MiFID 2 alone forces sub-μs precision. Million times less than the leap 1 second. NTP minute away is good for displaying date on the workstation, not for many of the devices that are critical to the modern world.

MiFID 2 does not require nanosecond accuracy. It's something like 100 microseconds in the strictest case.

Some MiFID reports require microsecond or perhaps nanosecond precision, but that's really just a formatting requirement "please write your timestamps with six figures after the decimal point."

Re: Ask HN: Are systems ready for the first negative leap second?

#35

Post by SeanAnderson »

I don't think we're going to do any negative leap seconds.

https://www.yahoo.com/news/science/articles/international-ti...

I think we're voting to change to a leap hour in early 2027. Or I'd assume we're going to go that route instead of continuing to entertain the tech nightmares.

Re: Ask HN: Are systems ready for the first negative leap second?

#36

Post by voxic11 »

wmf wrote: post #3

Systems are absolutely not ready. Leap seconds are a bad idea and negative leap seconds are worse. Just don't do it and let the drift cancel out.

Explain why negative leap seconds are worse? Intuitively it seems like normal leap seconds would cause way more issues, or at least not more.

Re: Ask HN: Are systems ready for the first negative leap second?

#37

Post by StevenWaterman »

jMyles wrote: post #18
yen223 wrote: post #11

Earlier quoted context omitted.

I don't think we can predict ahead of time whether we'll need a leap second or not If the question is "why bother syncing time to Earth's orbit around the sun at all", I don't have a good answer for that except at this point, it's tradition.

We can set some rasterization floor, such as like 3 minutes or something, and live with that. Correcting for a 3-minute offset every few millenia seems easier than trying to understand all this minutia about wobble and aquifer management and whatever else goes into a leap second.

I'm pretty sure that's the plan. Currently they're legally bound to keep it within 0.9s of solar noon (or something like that) but in 2035 it's changing to +-1 minute, which basically kicks the can down the road for another century or so

I say we let it reach 15 minutes then countries can solve it themselves by shifting timezone by 15 mins. Since making sure solar noon matches noon on the clock, is the point of timezones existing in the first place

Re: Ask HN: Are systems ready for the first negative leap second?

#38

Post by gmuslera »

knorker wrote: post #25
wmf wrote: post #3

Systems are absolutely not ready. Leap seconds are a bad idea and negative leap seconds are worse. Just don't do it and let the drift cancel out.

What's worse about negative leap seconds? The "experienced" time by systems will just look like they froze for a second. Added leap seconds are worse, surely, as time goes backwards.

Suppose being charged by time used to run your tasks. Then your task takes -1 second, you will be charged zero, 1 second, or 18 quintillon seconds?

Re: Ask HN: Are systems ready for the first negative leap second?

#39

Post by happytoexplain »

thomashabets2 wrote: post #29

I'd say yes we are ready. gettimeofday() should never be used to measure time[1], but at least with a negative leap second it's monotonic. We'll just get some poorly coded stuff claim that an operation took 1100ms instead of 100ms. Not great, but not -900ms. Well, I say that, but per my link here F5 load balancers at least used to keep track of TCP connections using gettimeofday. And it's annoying that libpcap delive…

> gettimeofday() should never be used to measure time

And yet, even as somebody who has no idea what platform you're referring to, I can still guarantee you that gettimeofday() is used to measure time on that platform. This is how software works, unfortunately.

Re: Ask HN: Are systems ready for the first negative leap second?

#40

Post by ssl-3 »

SeanAnderson wrote: post #35

I don't think we're going to do any negative leap seconds. https://www.yahoo.com/news/science/articles/international-ti... I think we're voting to change to a leap hour in early 2027. Or I'd assume we're going to go that route instead of continuing to entertain the tech nightmares.

We've on track to do something different before the end of 2035: https://en.wikipedia.org/wiki/Leap_second#Phase-out_and_futu...

Shifting to a leap-minute feels close-enough to me: We might get one every 50 or 100 years. A lot of us reading this today will never live to see a leap-minute, but it's close enough that we'll still have it collectively in-mind when it it needs to happen. (And if we screw it up at that time, the outliers will only be off by a minute. Not so bad.)

A leap-hour, meanwhile: That kicks the can so far down the road that we'll probably lose track of it completely. ~6,000 years is a very long time; society will be a very different thing by then. Leap-hours seem to me to be moral equivalent to the "fuck it, let's just give up" option.

edit: accidentally a word, and fixed an off-by-an-order-of-magnitude error on the approximate years required for a leap hour

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