[HN Gopher] No leap second will be introduced at the end of June...
___________________________________________________________________
No leap second will be introduced at the end of June 2026
Author : speckx
Score : 61 points
Date : 2026-03-09 12:15 UTC (10 hours ago)
(HTM) web link (lists.iana.org)
(TXT) w3m dump (lists.iana.org)
| wlkr wrote:
| Interesting! There's a _lot_ I don 't know about this, but I know
| a little more now. I'll admit, I naively thought this would be
| more regular than it appears to be [0].
|
| [0]: https://en.wikipedia.org/wiki/Leap_second
| butILoveLife wrote:
| They teach us Scientific Realism in school, but reality is that
| we are really using Instrumentalism.
|
| That said, no one wants to admit it, so contemporary science
| follows Falsification, where we find ways to not actually make
| claims about reality. (Which as an Instrumentalist/pragmatist,
| I love Karl Popper, its just not metaphysical truth. And that
| would break Popper's heart)
| voxl wrote:
| A distinction without a difference. The only way we can
| interact with the world is via senses, via instruments, via
| measurement. We can rehash solipsism, but seeing as how that
| is an immediate dead end we all agree there is a physical
| reality. If there is in fact a reality, then we are measuring
| something real.
| butILoveLife wrote:
| >we are measuring something real.
|
| I think it matters. No the planets are not doing circles
| around the sun. Circles don't actually exist, they are
| doing elipses.
|
| Also 'real' has quite a few meanings. If I ask the question
| 'Are you closer to a keyboard or the gym?' does that
| question exist?
|
| This kind of stuff does end up mattering. It becomes much
| more noticeable in psychology (and biology). If you read
| Freud, Adler, or Jung, you will say 'Oh extrovert! I've
| seen that before!' But then you realize its vague and
| almost always true. Its like a horoscope.
|
| So if we think there is a truth to reality, we look for
| perfect relations. If we think its impossible for humans to
| figure out, we look for best fits.
| riskassessment wrote:
| > They teach us Scientific Realism in school.
|
| I'd argue the opposite is true for anyone who has studied
| statistics which is largely built on Instrumentalism (think
| George Box: 'All models are wrong, but some are useful') and
| Popperian falsification (Null Hypothesis testing). We are
| absolutely taught to treat models as predictive tools rather
| than metaphysical truths.
| butILoveLife wrote:
| Statistics is even presented like metaphysical truth. Or at
| least my experience in engineering school.
|
| And taking fluid dynamics, we used renyolds number, which
| is a made up ratio that helps for decision making... Its
| not like when we answered questions, we could answer the
| grey area we are discussing.
|
| If I had to guess, I think its due to western civilization
| being built of Platonism (and even Aristotle was infected).
| Our science and morality is later built by platonic
| realism. Only in the last 100-ish years are we starting to
| get over it.
| exac wrote:
| No they do not teach Scientific Realism in schools. We're
| taught the scientific method and then build upon that.
|
| I can see how someone could misunderstand or forget what
| they're taught though.
| imglorp wrote:
| Responding to a deleted comment:
|
| > ... the "invisible infrastructure" of the web; balancing
| historical accuracy with the technical need to minimize zone
| fragmentation is a much more complex trade-off than it appears on
| the surface ...
|
| The complexity goes up tremendously if some condition is rarely
| encountered: eg leap second. This means it gets pushed to a
| "corner case" and tested more lightly and more rarely.
|
| At $work around 2014 we had three different hardware GPS types
| which we used for precision timekeeping; some chips,
| daughterboards, and firmware. One day a leap second arrived -- it
| gets broadcast to aGPS hardware a day ahead of time -- and all
| three implementations handled it differently. One handled it, one
| did something else like ignore it, and I think one even bricked
| itself. That situation was less than bueno.
| throw0101d wrote:
| > _The complexity goes up tremendously if some condition is
| rarely encountered: eg leap second. This means it gets pushed
| to a "corner case" and tested more lightly and more rarely._
|
| There is some talk of eliminating the leap second, which would
| over time have the Earth and sun diverge with regards to noon
| and such. One 'answer' to this concern is to have a 'leap hour'
| or something in the future (some future generation's problem,
| not ours): but given that people can't even get February 29th
| correct _now_ , and it happens _regularly_ , I don't see how a
| one-off event would be made to work. It'd be a huge
| coordination problem.
|
| Just look at the introduction of the Gregorian calendar: it was
| _slightly_ off since the time of Julius Caesar, but that minor
| error added up over time, to the point that to get the
| equinoxes /solstices back to where they 'should' be _10 days_
| had to be removed with the Gregorian calendar. And because of
| politics (or a religious flavour) it took a long while for
| everyone to get on the same page.
| tialaramex wrote:
| The calendar adjustments are because the planet's _constant_
| orbital period isn 't a whole number of days.
|
| The leap seconds were an attempt to have wall clock time map
| to the planet's rotational angle consistently despite the
| problem that the planet's spin _varies_ unpredictably.
|
| Yes the "leap hour" is a legal fiction of course. In reality
| in the event anybody cares about this in the distant future
| they will make the kind of "drastic" changes you've probably
| experienced twice a year for your whole life and barely
| noticed... More likely because the drift is so incredibly
| slow they won't change anything.
| throw0101c wrote:
| So lunar tidal forces are slowing the rotation, but
| (recently?) Earth mantle/core is causing a speed up, but
| climate change and melting ice is contributing to the slow
| down side:
|
| * https://www.scientificamerican.com/article/leap-seconds-
| may-...
|
| * https://scripps.ucsd.edu/news/global-warming-influencing-
| glo...
|
| The general trend is slowing down. Apparently (?) once the
| day gets to be 24h+0.001sec (+1 millisecond), a leap second
| would occur about every 1000 days; then when it becomes
| 24h+0.002sec, a leap second would occur about every 500
| days; when it reaches 24h+0.003sec, a leap second would
| occur about every year; etc.
| amenghra wrote:
| IMHO the correct way to handle leap seconds would have been
| at the same layer as timezones, i.e. a display-only thing.
| Timezone databases are regularly updated, you push out leap
| second updates there. In the worst case, people's clocks are
| off by one second but all the underlying timing logic doesn't
| crash.
| Polizeiposaune wrote:
| I fully expect in such a regime, people would be
| complaining about how the leap second insertion caused
| their recurring meeting to shift from 9am to 8:59:59
| Palomides wrote:
| you can use TAI (international atomic time, basically UTC
| without leap seconds) if you want to be serious about it
|
| I'm a fan but it's rare for anyone else to agree!
| wmf wrote:
| We had a leap hour yesterday...
| throw0101d wrote:
| > _We had a leap hour yesterday..._
|
| Prescheduled.
|
| Now tell everyone we're having one June 30, 2029, and see
| how things go.
| wmf wrote:
| If we eliminate leap seconds, we'll need a leap hour in
| ~500 years. It could be announced 50 years in advance.
| throw0101c wrote:
| > _It could be announced 50 years in advance._
|
| Which is about how long it took for folks to switch from
| the Julian to the Gregorian calendar.
| wmf wrote:
| In the US DST was changed in 2005 and the change went
| into effect in 2007.
| tmp10423288442 wrote:
| It took much longer than that, although to be fair the
| Catholic countries had switched in much sooner than 50
| years.
| zamadatix wrote:
| Leap seconds have so many problems beyond the time
| adjustment. It's a small/odd enough adjustment interval that
| there are wildly different approaches like leap smears. On
| top of being so small, it's rare enough (~every 2 years),
| depending on how a system is used, lack of proper handling
| might not be obviously apparent or lack of obvious problem in
| one implementation ignoring it may lead to lack of care in
| another implementation which would have a problem ignoring
| it.
|
| Leap hour replaces all of that with what is more or less
| equivalent to a change in DST rules (except for more time
| zones at once). DST changes don't go perfect either by any
| means... but we do them regularly enough without the world
| crashing down that doing an additional shift change of an
| extra hour every 5000 years is almost certainly less hassle
| and breakage than the leap second approach breaking things
| every ~2 years.
| phicoh wrote:
| It is way more easy to let UTC (without leap seconds) just
| drift away from the zero meridian and move countries to
| different time zones when convenient. We mess around with
| daylight savings time often enough that nobody will notice
| if we have change local time every couple of thousand
| years.
| throw0101d wrote:
| DST changes are pre-scheduled. Throwing a random hour
| in/out at (say) June 30, 2029 may be something else. Unless
| the jump is treated as a TZ change in _tzdata_?
| recursivecaveat wrote:
| Yeah you treat it as a time zone change where every zone
| moves over (or every country moves to the adjacent zone
| maybe). You can schedule it N years in advance. It's
| definitely not 0 disruption, but it's very manageable.
| Regions change TZs or toggle DST frequently enough that
| we can handle it.
| philwelch wrote:
| > There is some talk of eliminating the leap second, which
| would over time have the Earth and sun diverge with regards
| to noon and such
|
| "Over time" really glosses over how much time it would take.
| In 500 years there might be half as much divergence between
| solar noon and 12:00pm as we intentionally inflict on
| ourselves with DST, or that France and Spain inflicted on
| themselves in the 1940's so they could share a time zone with
| Germany. By the time anyone will even notice we will probably
| change time systems for other reasons anyway. It's not even
| remotely comparable to the Julian/Gregorian issue, which
| dealt with leap _days_. Each day has 86400 seconds.
| b112 wrote:
| If you think you're going to steal days off my life, you've
| got another thing coming buster!
| euroderf wrote:
| > There is some talk of eliminating the leap second, which
| would over time have the Earth and sun diverge with regards
| to noon and such.
|
| <rant> It won't happen on a human scale. So why oh why do we
| screw around with this moronic leap-second nonsense ? Oh
| dear, in the year 4000 noon will arrive three minutes earlier
| compared to now. So? </rant>
| michaelt wrote:
| _> One 'answer' to this concern is to have a 'leap hour' or
| something in the future_
|
| We've had 27 leapseconds in the last 54 years [1] - an
| average of 0.5 seconds per year.
|
| At that rate, solar time will drift by 60 seconds over the
| course of 120 years. Drifting by 10 minutes will take 1200
| years.
|
| The leap hour will be in 7200 years, around year 9226.
|
| [1] https://en.wikipedia.org/wiki/Leap_second
| throwup238 wrote:
| _> The leap hour will be in 7200 years, around year 9226._
|
| 7200 years ago the Neolithic revolution was still in full
| swing and many of the most famous megaliths like Stonehenge
| hadn't even been built yet. The first real state, the
| Sumerian civilization, hadn't formed yet in Mesopotamia.
|
| Personally, I'm very comfortable making this someone else's
| problems 7200 years from now. If they're still having basic
| coordination issues then it's their own damn problem.
| refulgentis wrote:
| "Basic" made me lol :)
| fanf2 wrote:
| Yeah. There's also the issue that the earth's rotation is
| slowing down, so over the long term leap seconds would
| become more and more frequent. There's a point when the
| earth is slow enough that leap seconds need to happen
| nearly every month, and by that point they are no longer a
| workable solution to the problem. That is expected to take
| a few thousand years, comparable to the point where a leap
| hour would be needed if there were no leap seconds.
| clickety_clack wrote:
| In British Colombia they're locking into daylight savings
| time, so I think it's safe to say that people aren't really
| bothered by solar accuracy.
| TurdF3rguson wrote:
| >There is some talk of eliminating the leap second
|
| The concern, of course, is that some universes eliminating
| them while others don't can puts us out of sync. This creates
| a wobble that could potentially throw us out of Hilbert
| space.
| dijit wrote:
| Just here to reinforce your point.
|
| The last leap-second I encountered (also the 2014 one) crashed
| my MySQL databases.
|
| you wouldn't assume that it depends on time like that, because
| honestly why would it? "surely it's fine, NTP corrects drift of
| a second fairly frequently"- but a leap second is not a drift,
| it's something quite insane unless your primitives are solid.
| Nobody would test for this.
| imglorp wrote:
| Yes I would assume that the NTP daemon would handle a leap
| second arrival with guarantees of (1) gradual application
| over a longer period and (2) never moving the clock
| backwards, only slowing it a little.
|
| I wonder if all NTP implementations don't follow those
| guarantees?
|
| Oh and another app that hates clock jumps used to be sshd; it
| would just bail out and drop all connections. We found that
| out while chasing ANOTHER bug in SunOS on a T4: they didn't
| have it mutexed right so it possible to read its RTC register
| while it was in the middle of getting updated so the client
| would read a garbage time. We chased NTP for a week before
| realizing it was the kernel.
| leni536 wrote:
| The insanity is that both NTP and unix timestamps need to
| be wound back during a leap second, as well as computer
| hardware clocks. If we just had monotonic clocks everwhere
| and adjusted for leap seconds in presentation then we
| wouldn't have many of the associated problems.
|
| It's not like we wound back by 24 hours on leap days, that
| would be insanity. So in addition of leapseconds being a
| rare problem, it's also handled in a uniquely bad way.
| throw0101d wrote:
| There was some talk about a negative leap second+ a few years
| ago:
|
| * https://www.npr.org/2024/03/30/1241674216/climate-change-tim...
|
| + T23:59:58Z would have skipped/suppressed :59 and gone to
| T00:00:00Z.
| netsharc wrote:
| You make it sound like time labels like "23:59:58Z" can perform
| actions (e.g. to skip or "suppress").
|
| I had to look it up: https://www.timeanddate.com/time/negative-
| leap-second.html . In proper words, the clock ("the one
| humanity agrees to use) would skip 23:59:59Z.
|
| I wonder how much chaos a minute that only has 59 seconds would
| cause. Measurements would be off by that missing second (e.g. a
| pipeline delivering fuel at 60 liters/minute would surprisingly
| only have 59 liters in that minute..).
| throw0101c wrote:
| > _I wonder how much chaos a minute that only has 59 seconds
| would cause._
|
| The FreeBSD folks test(ed?) their code for these things and
| it works:
|
| * https://lists.freebsd.org/pipermail/freebsd-
| stable/2020-Nove...
|
| Of course third-party userland code understanding what
| happens is another thing.
| SeanDav wrote:
| I assumed that leap seconds could be determined algorithmically,
| it appears I assumed badly. This is a bit of a can of worms...
| toast0 wrote:
| They basically are, the algorithm is something like:
|
| At the beginning of january and july, observe the difference
| between UT1 and UTC. If the difference is >= 0.6s, a leap
| second will be inserted at the end of june/december. Publish
| the results here: https://hpiers.obspm.fr/eoppc/bul/bulc
| pocksuppet wrote:
| This is true. They look at how much the earth spun, and
| whether it was more or less than 86400 seconds/day average.
| This can't be done without external data. It's not a pure
| mathematical algorithm.
| xg15 wrote:
| Waiting until Trump discovers that the earth rotation service
| exists and forces them to insert a negative leap second just
| because he can.
| Vvector wrote:
| Leap Seconds need to be abolished. The only people who need it
| are Astronomers. They could just use an offset. Implementing leap
| seconds correctly is a huge burden, for no gain.
|
| Where I live, high noon today occurs at 1:03 PM. No one is
| complaining that it is 3 minutes (or 63 minutes) off. It's a non-
| issue for 99.9% of the population.
| coldpie wrote:
| Hmm. I understand that perspective, but I'm not sure I agree.
| It does seem to matter over a relatively short & realistic time
| scale. According to the Wikipedia page, there have been 27
| seconds added since 1972, which is only 44 years ago. At that
| rate, that's about 1 minute per 100 years. We have many systems
| that have existed for several centuries and I think it's not
| unreasonable to start making plans for systems that may exist
| for millennia, where you're starting to talk about a 10+ minute
| offset at the current rate.
|
| But I do think there is a valid argument that the infrequency
| of these events cause more issues than maybe one large
| adjustment 500 years from now would cause. Not sure where I
| land on this one.
| 8fingerlouie wrote:
| > since 1972, which is only 44 years ago
|
| Thanks for making me a decade younger :)
| ralferoo wrote:
| The problem is that Earth's rotation isn't consistently
| faster. Some years leap seconds need to be added, some years
| they need to be removed. Would be far better to leave them
| alone, let them average out, and as the GP said let the
| people who care about this add the offset they need.
| coldpie wrote:
| > Some years leap seconds need to be added, some years they
| need to be removed.
|
| Is that true? Per Wikipedia:
|
| > Since [1972], 27 leap seconds have been added to UTC,
| with the most recent occurring on December 31, 2016. All
| have so far been positive leap seconds, adding a second to
| a UTC day; while a negative leap second is theoretically
| possible, it has not yet occurred.
|
| Either way, it's due in part to Earth's rotation slowing
| down, so the average drift would still be non-zero.
| ralferoo wrote:
| We've not had to apply negative leap seconds yet since
| leap seconds were introduced in 1972, but that wasn't the
| point.
|
| The time period of the Earth fluctuates a lot [0] and
| actually in 2020 it was less than 24 hours, but not a
| large enough change to warrant a negative leap second. If
| you go back to the 1940s, we would had needed negative
| leap seconds if we had leap seconds at all then, and
| going back 150 years we would have needed multiple
| negative leap seconds every year for several consecutive
| years.
|
| What we can say is that on average, it is close enough to
| 24 hours and the average over hundreds of years is even
| closer to 24 hours that it's not worth adding these extra
| seconds as you'd then need to remove them again later on.
|
| [0] https://c.tadst.com/gfx/900x506/graphlength-of-
| day.png from https://www.timeanddate.com/time/negative-
| leap-second.html
| Vvector wrote:
| Can you explain how a 10 minute offset would affect you in
| any way?
|
| For 99% of the world today, high noon =/= 12:00:00. Nothing
| breaks because of this. The world continues to run.
| philwelch wrote:
| You make a good argument for the opposite of your conclusion.
| If you're planning a system that's supposed to last for
| millennia, that system shouldn't depend on the fiat of the
| International Earth Rotation and Reference Systems Service.
| zarzavat wrote:
| Let's just do leap minutes. If humanity survives long enough
| to witness a leap minute without destroying ourselves then
| that's ample compensation for the minor inconvenience.
| 8fingerlouie wrote:
| I mean, in 53 years we have added 27 leap seconds, so in 119
| years you'll have to set your alarm a minute earlier if you
| still want to arrive on time.
| xorcist wrote:
| Unless you want to abolish timezones entirely, which would
| simplify clocks but complicate a whole lot else in society,
| you're going to need leap- _something_. Would leap minutes or
| hours really be much better? The idea that doing things less
| often causes more problems is a reasonable one.
| delecti wrote:
| In the 56 years since UTC was established, there have only
| been 37 leap seconds. At that rate it would take more than
| 5400 years before it would affect solar noon more than DST
| does. I'm more than okay kicking the can that far down the
| road in the name of avoiding all the ridiculous solutions
| that are needed to accommodate leap seconds. We've endured
| these headaches to potentially solve a problem for people who
| might not even still be using UTC.
|
| Compare that to removing the leap _day_ , where the start of
| seasons would be noticeably affected within just a few
| decades. Hundreds of years ago, a pretty insignificant
| headache was invented which is providing constant payoffs.
| paulddraper wrote:
| > The only people who need it are Astronomers.
|
| And anyone that cares about the relationship of the time of day
| and the position of the Sun.
|
| Granted, it's not a lot, only a minute per century.
| Vvector wrote:
| Yet high noon at my current location comes at 12:03 (1:03
| with DST). It's three minutes off. If I lived further west in
| my timezone, noon would come much later.
|
| How can people manage with noon off by minutes, yet want
| leap-second accuracy every 6 months?
| paulddraper wrote:
| More like every 2 years.
|
| But yes, point taken.
|
| The counterpoint is that it costs little.
| euroderf wrote:
| > The counterpoint is that it costs little.
|
| Radical changes to time-related software cost little ?
| Stop press !
| paulddraper wrote:
| What radical software changes are you doing?
|
| I haven't once done a single software upgrade related to
| leap seconds.
| phicoh wrote:
| Which means that time changes slowly enough that we don't
| notice. At some point everybody goes work half an hour
| earlier because it makes sense. Schools start earlier, shops
| open earlier. It doesn't have to be coordinated worldwide.
| Every region or even town can have its own customs. Then
| people notice they are in the wrong time zone and a country
| moves to a different time zone.
|
| Statistically, nobody on Earth knows what UTC is. People know
| about their local time zone and how it related to time zones
| in other countries. Where the position of the sun is relative
| to UTC, almost nobody knows.
| bloak wrote:
| I think the best solution for minimising overall _long-term_
| hassle is to switch to using TAI internally and UTC for
| display.
| himata4113 wrote:
| How about a leap minute instead so we only have to worry about
| this when it's not a problem anymore :)? We will either hit the
| fermi filter or accend intelligence.
| layer8 wrote:
| The length of day increases by around 1.7 milliseconds per
| century long term (due to the moon's gravity continuously
| slowing down Earth's rotation), which without leaps seconds
| translates to around one total minute per century. Note that
| this is cumulative: next century you will need two leap
| minutes, and so on. Of course, there are significant shorter-
| term variations in Earth's rotation due to other factors, so it
| isn't quite that smooth in practice.
|
| There was a resolution in 2022 to make a decision in or before
| 2035, to increase the allowable deviation from one second to a
| longer interval, like one minute. But that would become more
| frequent in the long run as well, and likely would still cause
| disruptions whenever it happens. Though on the other hand there
| would likely be a longer advance notice for it as well.
| himata4113 wrote:
| I think in 100 years more or take if the exponential curve
| doesn't level off we're gonna each near super intelligence
| and some form of fusion at minimum. At worst we just
| eradicate ourselves.
| wmf wrote:
| That's much worse than the Y2K problem.
| himata4113 wrote:
| The idea is that we've advanced so far that it is simply not
| a problem anymore.
| alentred wrote:
| I would rather suggest a contrary: do smaller increments more
| frequently. This way it is easier to test and if something goes
| wrong you know it quicker. Kind of like running your CI
| pipeline on every commit vs nightly. Going to millisecond
| adjustments seems, however, very impractical.
| sltr wrote:
| Next up: DOGE cancels leap seconds. /s
| idiotsecant wrote:
| We should just have a standards body that meets each decade and
| decides what epoch time every day for the next 10 years
| officially starts on. Everyone knows ahead of time how it will
| work, software updates have predictable change intervals, it
| allows us to refresh time based on policy decisions, and it uses
| something sane as the backbone of the system.
___________________________________________________________________
(page generated 2026-03-09 23:01 UTC)