Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

news.ycombinator.com

Post reply on HN
Print view View original

61–70 of 100 posts

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

#61

Post by hunter2_ »

OneDeuxTriSeiGo wrote: post #58
gmuslera wrote: post #38

Earlier quoted context omitted.

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?

That shouldn't be the case? When a negative leap second is applied it just means that 23:59:59 is skipped. The seconds go 56 57 58 0 1 2 3. vs a positive leap second where time goes 56 57 58 59 60 0 1 2 3. So if you are billed by time and it's tracked via a timer then your time is still accurate but if it's tracked by reading your start and end time then your billing will just read an extra second. Positive leap seco…

> just read an extra second [...] accidentally trigger watchdogs

Well, this seems to touch heavily on the concern: if your job normally takes 0.1s and costs $100, it could accidentally be considered to have taken 1.1s and therefore cost $1100. This is quite contrived, but if you consider that some people put very infrequent cron jobs at the top of the hour (which isn't typically the best idea, but I digress) and it might start just ahead of what the billing system considers to be the top of the hour, theoretically there's something to this concern.

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

#62

Post by duskwuff »

FabHK wrote: post #52
_alternator_ wrote: post #48

You may be relived to know that Unix epoch time does not have this problem. But you may also be horrified to know why. First, epoch seconds are not the numbers of seconds since 1970/01/01. This is a lie we tell to children. Rather, epoch seconds are the number of days since 1970/01/01 * 86400 plus the number of seconds since midnight. Leap seconds, to epoch time, don't exist. Or maybe they are double counted. Or mayb…

Indeed. I like to say, we would like three things to be true: 1) Every day has 86400 seconds. 2) Every day is from noon (sun exactly above) to noon (sun exactly above). 3) We use SI seconds. You can't have all three. Pick any two: 1, 2, not 3: What you describe. Day has 86400 seconds, we keep in sync with the sun, but we tweak the seconds a bit. There are different versions, like epoch time, or UT1. 1, not 2, 3: Ever…

Unless you're an astronomer, you probably don't care about condition 2. Many countries still shift wall time around by an hour twice a year for DST - if people are okay with that, solar time being offset by a few seconds is insignificant.

Even for astronomers, I suspect that preserving conditions 1 and 3 is probably more valuable than 2. It's easier to correct for the uneven rotation of our planet than for an uneven timescale.

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

#64

Post by _alternator_ »

not-a-llm wrote: post #57
lesam wrote: post #53

Earlier quoted context omitted.

Until you work in financial markets and you want to measure latency vs a bunch of other servers you don't own, all of whom pick different smears (and some of whom aren't sure in advance which smears).

financial markets dont trade when the smears happen (NYE)

They can happen mid-year too. They usually don't for this reason, but they can.

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

#65

Post by weakened_malloc »

not-a-llm wrote: post #57
lesam wrote: post #53

Earlier quoted context omitted.

Until you work in financial markets and you want to measure latency vs a bunch of other servers you don't own, all of whom pick different smears (and some of whom aren't sure in advance which smears).

financial markets dont trade when the smears happen (NYE)

Depends on the market. Crypto and prediction markets wont stop.

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

#66

Post by lokar »

toast0 wrote: post #12
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.

negative leap seconds aren't too bad. jumping forward a second won't lead to a time loop like jumping back did on several systems (some twice!)

Unless you have something scheduled for that second.

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

#67

Post by stingraycharles »

_alternator_ wrote: post #48

You may be relived to know that Unix epoch time does not have this problem. But you may also be horrified to know why. First, epoch seconds are not the numbers of seconds since 1970/01/01. This is a lie we tell to children. Rather, epoch seconds are the number of days since 1970/01/01 * 86400 plus the number of seconds since midnight. Leap seconds, to epoch time, don't exist. Or maybe they are double counted. Or mayb…

And this, ladies and gentlemen, is why you use a proper datetime library rather than doing epoch arithmetic yourself.

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

#68

Post by Charon77 »

duskwuff wrote: post #62
FabHK wrote: post #52

Earlier quoted context omitted.

Indeed. I like to say, we would like three things to be true: 1) Every day has 86400 seconds. 2) Every day is from noon (sun exactly above) to noon (sun exactly above). 3) We use SI seconds. You can't have all three. Pick any two: 1, 2, not 3: What you describe. Day has 86400 seconds, we keep in sync with the sun, but we tweak the seconds a bit. There are different versions, like epoch time, or UT1. 1, not 2, 3: Ever…

Unless you're an astronomer, you probably don't care about condition 2. Many countries still shift wall time around by an hour twice a year for DST - if people are okay with that, solar time being offset by a few seconds is insignificant. Even for astronomers, I suspect that preserving conditions 1 and 3 is probably more valuable than 2. It's easier to correct for the uneven rotation of our planet than for an uneven…

Condition 2 are pretty much hard to get. Happens everytime in the equator, happens only twice a year in most countries, hopefully never happens in the n/s pole

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

#69

Post by Telaneo »

duskwuff wrote: post #62
FabHK wrote: post #52

Earlier quoted context omitted.

Indeed. I like to say, we would like three things to be true: 1) Every day has 86400 seconds. 2) Every day is from noon (sun exactly above) to noon (sun exactly above). 3) We use SI seconds. You can't have all three. Pick any two: 1, 2, not 3: What you describe. Day has 86400 seconds, we keep in sync with the sun, but we tweak the seconds a bit. There are different versions, like epoch time, or UT1. 1, not 2, 3: Ever…

Unless you're an astronomer, you probably don't care about condition 2. Many countries still shift wall time around by an hour twice a year for DST - if people are okay with that, solar time being offset by a few seconds is insignificant. Even for astronomers, I suspect that preserving conditions 1 and 3 is probably more valuable than 2. It's easier to correct for the uneven rotation of our planet than for an uneven…

I agree. The difference in how much we're out of sync with the sun is tiny and also completely inconsequential in the vast majority of cases, especially compared to the trouble of the alternatives. By the time the difference is relevant or noticeable, I sure hope we have a better way of tracking time.

If anything, it's probably for the better to completely disconnect the measurement from it's old standard, the same way imperial measurements are now defined using SI units as a baseline, and how 1 AD isn't actually the year of Christ's birth. It's OK that the actual measurement is off from what it was once based of, so long as we all agree how we're defining our units.

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

#70

Post by Telaneo »

ssl-3 wrote: post #40
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 tim…

> Leap-hours seem to me to be moral equivalent to the "fuck it, let's just give up" option.

Sometimes, doing nothing is the right option. Sometimes, giving up is the right option. I believe this is one of those times. The alternatives seem worse to me, and the fact that it's even being considered by the curators of time would seem to indicate it's not a completely invalid option.

Post reply on HN