Why Leap Seconds Cause Glitches
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- čas přidán 29. 06. 2015
- (EDIT: Of all the things not to fact-check! It's UTC, not UCT. Which is short for Coordinated Universal Time, because reasons. Well, that's embarrassing.)
tomscott.com - / tomscott - There's a leap second tonight! And while there's not the Y2K-scale of disaster being predicted for it, there are probably going to be a few problems. Here's why computers have trouble with something that should, in theory, be pretty simple.
I swear to god, Tom could talk about dirt and it'd be interesting.
Kayla Burney IKR i will be interested in this kind of "nerdy" stuff but without him and his voice i will fall asleep
dirt is very interesting.
Soil microbiology?
Randy Zhu
Another term is “pedogenesis”, which is the *formation* of dirt. Also “pedology”, which revolves around *studying* dirt.
PS: Ignore the “pedo-“ in the names, they’re not related to pedophiles however much they resemble dirt...
@@Operational117 iirc pedo-/paedo- has 2 meanings, 'child' and 'foot'. So someone with a foot fetish would, technically, be a pedophile/paedophile.
And then you get a call from mars...
and they say "excuse me, but we are on an entirely different time scale. one that includes an extra 40 minutes every day, and another set of time zones to boot"
and then you get a call from an artificially intelligent machine who informs us that our time zones are inferior
And then you get a call from Mercury. "Excuse me, but our day takes up 67% of our year. Also, you'll have to adjust for our retrograde using relativity. Also, we're burning to death, the average surface temperature is 340 K!"
Things like this are part of what UNIX time was meant to solve, thankfully.
Paul Kang And then Venus calls and says, "Hey, our day is longer than our year. Oh, and it's very hot and stifling down here!"
Are the stock markets closing for an hour or for 60 minutes and 1 second?
Or 59 minutes and 59 seconds, since in principle, leap seconds can go either way.
Hopefully forever.
Zeldagigafan
Well you got your wish now huh
Gamepocalypse Gaming bruh
2h 2s
We're surpassing the leader with this one 🗣️
Ah yes, UTC, the abbreviation compromise. The English wanted CUT (Coordinated Universal Time) and the French wanted TUC (Temps Universel Coordonné), so they compromised and chose UTC. That way, everyone is wrong!
Universal Time Compromise
What? No. The U in UTC has nothing to do with Unix timestamps.
@@paddor
I never said it did. In fact, I said it stood for "Universal". As for relevancy, Tom brings it up in the description of this video.
@@paddor r/woooosh
Alex Larsen
I don’t know what you original comment was, so I’ll let you off on this one.
I was staring at that clock, waiting for it to glitch.
is it glitch
Same
Ikr
I've said it before, but I'd love to know how you do your research. You seem to find elements of topics that nobody else seems to be writing / making videos about.
It's mostly out of curiosity i'd guess. By simply asking yourself how and why things work and how they could go wrong you get so many topics to reserch on that you bearly have the time to cover them all
Ali Jardz Ali, how are you verified with 6,000 subscribers???
The explanations are in His head
DashFlash you can get verified at 1000 subs with 4000 hours of watch time
@@charliemcguire5051 that's monetization
Try dragging the time bar, and see the little thumbnail, you can see that the clock in the thumbnail always at .60
Cool!
Nice catch
ChoCo BenchMarker cool
That is so cool cause it 60 timebdjzq s eknfowncls......
Wilry Williams r/ihadastroke
Yeah, I definitely misread the title. I thought "Why leap seconds cause chickens" was a weird video...
haha xD
Every leap second, the number of chickens in the world doubles. Bad for farmers, good for food.
xDDDDD
"Strange phenomenoa causes farmers' chickens to undergo a process similar to mitosis every leap second."
"The reason for this is the Temporal Lobe inside each living chicken. This organ instructs the brain to immediately stop all thought and to immediately duplicate the chicken when it detects a leap second. Scientists have been using chickens for centuries to figure out when a leap second occurs, as they are the best and most reliable source for knowing when a leap second occurs. Throughout the years, we have found that if we simply remove this from chickens, they will no longer spontaneously duplicate, however, any and all offspring they have will have 2 Temporal Lobes, causing it to split twice instead of just once, *quadrupling* the number of chickens."
"While this spontaneous growth of chickens is great for the market, it is not sustainable. If we continue this trend, it's estimated that chickens will overcrowd the Earth in 2045, so it is necessary we find a way to stunt their growth."
@@nathancarver7179 just loa d a spaceship whit the chikens every few years and send it to the sun. the chikens dien and melt and thus cannot duplicate anymore, and bc we only sent most of them, not all of them, we still have chikens.
You know, every time I watch a video of yours, I think "the James Burke torch has been passed - and it's in very, very good hands." Please keep up the great work.
Wow, that is a great comment. How accurate. He needs to do so of those time cuts in his videos.
Steve Donoghue I wonder if a modern day take on "Connections" would be a good idea?
In our current world, which is more hyper-connected and less scientifically literate than ever? It would be a GREAT idea! Provided it had the right host - hence my original comment!
Steve Donoghue You do know James Burke's still alive, right? Retired, quite possibly, but he won't be passing on any torches for a while!
I'm very glad he's still alive, and he's still a fascinating speaker! In fact, "New Connections" could be a collaboration!
Meanwhile some internet forums tell you that you have to wait 15 seconds to post again just because you posted a few minutes before daylight saving time starts.
For the ball drop of 1988, organizers acknowledged the addition of a leap second earlier that day (leap seconds are appended at midnight UTC, which is five hours before midnight in New York) by extending the drop to 61 seconds, and by including a special one-second light show during the extra second.
Your videos never seem to bore me. I learned so much from your CZcams channel! I love it. I saw that this video was recorded on June the 30th. I had just arrived in London that day so I'm really sad that I missed an opportunity to tell you how much I appreciate your hard work for this CZcams channel. But anyway, keep up the good work and I am looking forward to see more interesting, entertaining and informative videos in the near future.
Thank you so much for close captioning your videos!!! I'm hard of hearing, but love your work, and sometimes it can be difficult to understand what you're saying-but this solves is greatly, thank you!!
I always love it when you do videos on computer science.
The few minutes I spend watching your videos just feel like an eternity. Your videos don't need to be long to be good! I like you because of that. :D
I just noticed that you used the American date format.
I think his audience is mainly American so it makes sense to do that.
I would actually love for the stock market to crash because the Earth doesn't spin in human compliant measures.
That way, astrologers can finally blame the stars for your ill fortune... and be right. Sort of.
Just a lil bit.
Sapphire Crook lol ;-)
You are now a week older
You are now 5 minutes older
Can't relate you are 4 days older
You are now 35 seconds older
I think the best way to deal with leap seconds is to have the client-side have a sort of "lookup table" that translates Unix time to whatever time format your country uses. That would mean Unix time would never have to change. Yes, you'd have to pull together a database of when these changes happen, but it would be in software separate from Unix.
In the case of the space shuttle, you could have the main computer on Earth translate Unix time and account for any leap seconds. You wouldn't have to update the shuttle, just update how the client PC interprets this data.
ong, that's what i thought about
0:17 nice
I don't get it.....
So is the leap second happening all at once at midnight UTC, or will it get tacked on at midnight in each successive time zone?
Spencer O'Dowd I believe it's at midnight UTC, so 8pm New York time. (In practice, it'll probably be whenever your computer next happens to poll a central server for time updates, but maybe some systems handle it naturally!)
Spencer O'Dowd Actually, the leap second is a random second of the day, elected by lottery. Nobody's told which or when, except for a select group of lizards across the biology classes of the world.
And once the second happens, the brain implants of these lizards broadcast, with enough coverage that the minor issues with lightspeed are not noticeable.
It was that, or having to put in a few exceptions on the phone network, and the nerds preferred the easy way out with lizards they had lying around.
***** NTP tells the clients that a second will happen or that it has happened for a period of 12 h or 24 h (left my standards in the other jacket) before and after it
Fun fact: The number after the "." in the dot is always a multiple of four
@Shawn Deer Williams oh yea
@Shawn Deer Williams this video isn't in 60fps. It's on 30 or 25 or 24 fps. I don't know
@Shawn Deer Williams The video is in 25 fps. The centiseconds increase by 4 every frame because 100/25 = 4.
I had a brief frame rate drop/glitch when you mentioned "sudden glitch in time" at the end of your video and I genuinely thought it was included as another way to make your point...
I used to work in Computer Operations for a major bank. Daylight Saving was the headache (we didn't run Unix). At the start, setting the clock forward was easy, just pause processing, reset the clock, resume processing. Going back was harder. We would shut down everything for an hour (usually 2am), then during startup the clocks would reset to the standard time.
Occasionally I watch your video on programming time and timezones (possibly with some slight sadistic glee at the back of my mind), and I can only imagine what this news must've done for your hypothetical programmer, making his hypothetical timecounting program
If they have these every three years or so why not just have a leap minute once every 180 years or so?
Sooo much easier to deal with.
LiamE69 Might as well say, why not have a leap century instead? That is even easier.
The point is to avoid inaccuracies before they become significant. A minute, or even several seconds would certainly be significant in many applications, say travel plans or orbital calculations.
T1Squid Sorry I am absolutely not buying that.
Why is it of vital of importance that 0 deg is within 1 second of UT1? To the best of my knowledge no rockets are actually launched from the meridian so any orbital calculation must already include a correction in time for longitude if accuracy is needed. Hell, even being 0.9 seconds out, which it is right now, translates to a miss of a target by 6-8km at orbital speeds, so clearly they are not just looking up the time on the pc and saying "that'll do" for the calculations.
Travel plans? Really?
Forgive me if my examples lack conviction. Maybe you know better than I do.
I was merely trying to illustrate, an off-time by a minute might be considered unacceptable, whereas a second might still be in tolerance. Where exactly, I am unaware.
If this is not the case, then I'll happily vouch for the leap century. Although I'm sure no one else will, since there will be years where the timing of the seasons won't adhere to our traditional understanding, depending on where you live.
I guess in critical calculations, a whole different time format would be used anyway.
We should create a new calendar starting in January 1, 1970. That would make this year 45.
We've had leap seconds before and I've never known all this discussion particular in the popular media about doom and gloom. It's almost like a Y2K revival and when it happens life will just carry on as normal like it's done with previous leap seconds.
This video explained to me what unix time is, allowing me to use it in my python code. Thank you very much.
Brilliant explanation. I wasn't sure, from the title, that you weren't going to over dramatise the effects but you didn't.
Dude, I love your videos.
WE NO DIFFING HAL W THIS ONE🔥🗣‼️🗣🔥🔥
I was right there! Yesterday. Can't believe I missed Tom Scott by one day.
Ah, you had a chance!
Love these videos, really interesting :)
"...it goes 23:59:60 AND THEN EVERYTHING BREAKS."
Great vid, didn't know about the problems of UTC.
I woke up wondering what would happen to the unix timestamp, thanks for the answer!
I like the leap smear solution. Computer programs are better prepared for a second being a little too short or too long, but they are not prepared for having the :60 in a datetime or a second being repeated/skipped.
Tom scott always amazing.
I'm so hyped for this leap second today!
3½ hours to go, fire up the BBQ and gather friends around the ol' shortwave to listen to WWV or your favorite local time signal station and listen to it tick off 61 seconds in that final minute. I'm giddy, I tell ya!
Hey @tom_scott. Can you do a video about the Canadian strategic maple syrup reserves and how it was stolen. I would love to see a video on this!!
Man, do I love these video's
TAI doesn't have leap seconds. It's just a straight count of seconds. As a result, it's something like 30 seconds ahead of UTC (don't know the exact value off the top of my head, and it keeps going up each year). GPS date zero was midnight on the 6th of January 1980 UTC (which was the only time it's ever matched up with UTC), giving GPS time an offset of 19 seconds relative to TAI.
Oh golly, it's Y2K all over again!!!
***** Nillie
i'm really talking about all the craze that it spawned
+loric loppi
Y2K Actually was a thing that actually would have done a LOT of damage - mostly financial. The very reason people like you think it was totally harmless LOLOL is because it actually got fixed. Which took a LOT of time and effort.
The only stupid part of Y2k was people thinking it'd be the end of the world, computers will EXPLODE, but those were rare.
+Fen Y Y10K is a huger problem
Why not keep a separate time related to unix time where the leap seconds are included?
Then you can have your cake and eat it.
But then you'll have two separate times to keep track of, instead of just one. Trouble all around.
@@Poppamunz not really trouble all around, use non-leap time for all math, and when need be, convert to leap time to display to humans.
So here's what I hope is the next question that has been resolved - does UTC or UCT have a solution for Leap Nanoseconds?
All my computer clocks are leap second aware (I know because I wrote all of them). To store times with leap seconds, I just add a billion to the number of nanoseconds during the leap second insertion. Also, `struct tm` officially supports 60, although not 61, but I guess 61 will never happen and that they will just use the secondary insertion slots if need or in extreme scenarios use other of band leap second insertions.
I wonder if aliens have to deal with leap seconds too…
I would really like to see "23:60" on a clock for a second
I'm pretty sure this is why Google maps was off by 400ft today. It kept thinking I was east of where I was when it is normally really accurate
I was actually fixing a leap second count for one of the utility functions at Google for this very leap second. Just happened to notice that the count hasn't been updated yet, figured it'd take me a few minutes to increment the counter and get approval for the change. Long story short, took two weeks and API changes in several libraries. Moral, a) Google takes error-checking very seriously, and b) dealing with any sort of time-keeping utility functions is really, really not fun. I'd say, "don't get me started on time zones," but I believe Computerphile has a video on that very topic.
So this is why when I hacked a virtual machine to run the system clock backwards, it caused all sorts of errors and weird behavior.
Love you videos, Mega interesting!
Maybe having two different Unix times would work... like one that counts leap seconds and one that doesn’t
@VisualPlugin the Multi-lingual Programmer damn, a reply to a two year old comment
Hmmm, a follow-up (if it hasn't happened) would be interesting, to see what effects it actually had 🙂
I don't know why we don't just divide time up between measurement and representation.
For example, have UNIXtime or similar as a basic second counter that is always going up, then use ephemeris data and rules to convert real time measurement into representations, like time of day, and day of year. We know the axial and orbital periodicity to a very high degree of accuracy, and can also deal with fluctuations via functions.
Both kinds of data have value and are important for different processes.
I was in Westminster just 5 days ago! such a familiar sight
Ah yes, the thing that made Tom go into madness on computerphile
Will it have an affect on your hammer time clock?
Would love to hear you talk about the 2038 problem!
i think my favorite thing about this video is the fact that we, the human beings on this planet, are basically correcting it saying it did it wrong so now we have to compensate, that's like a parent doing something wrong and their child compensating for it, its completely comical
tom scott's attempt to beat the system
"A stitch in time fills up space."
You're correct [in your description] it is UTC. Originally it was proposed as CUT by English speakers, and TUC by French, a compromise of UTC by the International Telecommunication Union was finalized. This conforms to the variants of UT0, UT1, UT2, UT1R, etc.
Speaking of time zones, this might just be interesting enough for a casual mention in a video: Ireland is currently on Irish Standard Time (which is the same as CET) and not on British Summer Time.
This is because Ireland's official timezone is "GMT+1" - that's our standard time. But we observe daylight savings, by putting the clocks back in the winter to "GMT". Which means, while we always have the same time as London, our "standard time" is still 1 hour ahead of London? Blame the Standard Time Act 1968. Before that, we just followed London time - even for those 40-odd years where we were independent and didn't technically have to.
Why??? You guys are living by west of Greenwich! Is it some show off to oneself "we are ~independent~ from Britain now"?
The file with the current timestamp glitch would just be overwritten in most cases. I did some file manipulation in C++ and it overwrites the file that I had.
Another option would be to include a leap second for every month. If that month doesn't actually have a leap second, it gets skipped. Otherwise, it gets used.
Better to include the absolute seconds instead of option 2. The system just provides basic date ABIs like duration, time, dates, etc. Durations include the leap second while clock time doesn't. Is there any problem with this?
I love this guy and his channel and voice and video so much 💖 😘😘
I'm gonna tag Hal for this one
I think we should only apply leap-seconds and skip-seconds the day the rules and formulas needed to calculate the next 5 occurrences of is written out on the wikipedia-page for the phenomenon.
UTC/UCT/CUT/whatever time confuses me. I always just call it UCT because in my mind it's 'universally coordinated time', which isn't what it is, but whatever.
The US National Institute of Standards and Technology says that it's because they didn't want to appear to favor one language (English or French) over the other, and so it couldn't be CUT (Coordinated Universal Time) or TUC ("temps universel coordonné", I think?)... so they chose UTC.
It's also to match with the other time standards, of which many are named UT-something.
I just completely bypass that issue and say GMT
This is a bit vague, does the Unix time stay on the same second for two seconds or just keeps counting up?
I think I saw you on the bus today coming from Westminster Abbey...I was too nervous to say hello but I'm pretty certain that it was you! I should have said hello -___-
I like how he says you can set the date/time on your phone months back and it probably won't mess anything up. Then a few months after people do exactly that and break their iphones
Samuel K for several reasons:
1. they set back the time several years, not months.
2. it's an iPhone what do you expect?
There could be an option 3 which is adjusting the time back by 1 second.
I do think not including leap seconds is better. By definition, the Unix timestamps is the number of seconds elapsed since 1 Jan 1970 UTC. We are talking about physical seconds, which have a definite, measurable time span. Including leap seconds wouldn't make the unix timestamp what is meant to be: number of elapsed seconds since 1 Jan 1970 UTC. And by the way, all this crazyness of leap seconds, leap years and timezones is because our obsession of having the sun up on our heads when it is 12:00
Amazon's AWS will do the leap smear as well.
Also, a former coworker worked on an exchange. They've begun worrying about *nano*second timescales for high-frequency trading. Orders of magnitude even more absurd if they had to deal with a leap second in there.
Seriously? They went from mili to nano? What about micro inbetween?
How about negative leap seconds? Do those cause glitches and if so, why?
Do all the devices on the world which is this time have like a clock in them running since 1970? Are they all synchronized?
apparently the General Conference on Weights and Measures has decided to abandon leap seconds by or before 2035. I wonder what problems that's causing or will cause
You sir are great! Thank you!
The black box that pops up with options is just barely too small
I'm confused. So in order to not have to update all the programs that interpret Unicode, we update Unicode. But now we have to change the time on all computers? that seems like even more of a hassle?
2:20 This is literally a plot point in the light novel "The Perfect Insider".
***** I spent my leap second wondering when Citation Needed would return.
Why not just two Unix time feeds? One with the seconds since 1970 in absolute terms (atomic clock-based), and one feed with the number of seconds in human time-keeping standard (year-based)? Programmers could just use the absolute one whether they're dealing with time passing, and the year based one whenever dealing with dates/day-night/hours, etc.
Not counting leap seconds doesn't break the rule that a larger UNIX time happened after a smaller UNIX time. However, it does break the converse rule that a later event has a larger UNIX time than an earlier event.
Ahhh Unix. I used to be a Unix administrator at JPL. Brings back memories :-)
Hey tom maybe is interesting for you to know. Stock trading companies pay exorbitant prices for buildings near stock markets just to be nanoseconds faster than they competitors.
We'll never be a able to count time with 100% accuracy
Regarding: "the Earth's orbit is slightly irregular." - shouldn't be that more like our time measurement is not matching the orbit and thus we have to adjust for that? So, the fault is not the an orbital irragularity, but how we set up time measurment... after all we have the mentioned leap years for the same reason, do we not?
Drudenfusz No, it's actually an irregularity! That's why they're only announced a few months in advance. (Also, I guess technically it's in the rotation, not the orbit, but I reckon that's close enough.)
Drudenfusz we have atomic clocks
they are few orders of magnitude more precise than earth's rotation, let alone its travel around the sun
The spin of the earth changes each day from wind, tectonic shifts and probably a few other things I can't remember at the moment. It would be hard to account for these tiny changes everyday, so they wait until they have slowed rotation down by a second and add that to our time.
***** Okay then, thanks, guess I have learned something new.
***** Indeed it's the rotation, not the orbit. Not really close enough either, given the causes are things like the Moon's tidal effects.
so why are leap seconds a thing? yeah earth's orbit is irregular, but if we don't do leap seconds in a million years we'll be what a minute off of "proper" astrological time?
In a million years? A lot more than a minute. It only takes a few decades to rack up a minute's worth of leap seconds. And keeping up with correct astronomical time is very important for technologies that operate on the principles of general relativity - like GPS networks.
but I thought the irregular drift meant we both gain and lose seconds. does that mostly balance out?
But atomic clocks keep the count for GPS. Neither of a pair doing so knows nor cares that the earth's spin was a little off. All that does is the rising sun.
+hornylink this is a somewhat late answer, but for everyone wondering: no it doesn't. The atomic second (SI second) is defined, so 24 * 60 * 60 s is slightly shorter than the average astronomical sun day (the time span between 2 times the center of the sun being exactly on zenit over the greenwich meridian). Therefore you always add leap seconds to the UTC so it never differs more than one second from GMT. Leap seconds never get removed.
Nope, leap seconds CAN be negative, in which case UTC jumps from 23:59:58 to 00:00:00. It's just that all 27 of them we got so far happen to be all positive. And that answers hornylink's question: no, they are not nearly equally probable, so they don't balance out.
Would a solution possibly be to keep track of two versions of UTC, one where you include leap seconds and one where you don't?
Programmer 1: "You did remember to use UTC2 and not UTC1 right?"
Programmer 2: "...wait what?"
The clock without leap second is called TAI. You can use that for timestamp but since we don't have a leap second forecast database, a given future TAI cannot be translated to UTC and vice versa. And a time variable in computer that can't mark future time would be so annoying that nobody will use that. Therefore, a computer system pick TAI or UTC, only one of them base on system purposes, and stick with it.
wt program u use 2 display both unix and utc time on screen?
Leap seconds always happen late on Jun 30th, or December 31st - if they are needed. The reason why it is 'interesting' this time for computers, and haven't been an issue in the past, is that the last leap second in June was 2012 - but that was on a weekend. Before that, the most recent extra second in June was 1997, and before apparently everything was connected up and online. So, it was never a problem before.
Alister Bulman what about 31st December 1998, 2005 and 2008? ;-)
nova No stock markets open - no issues, and much of the rest of the world is happily shut down for a day or two.
I don't remember ANY problems caused by the leap second the last two times so I don't understand the fear.
We should change time to BC (before computer 1969=1 B.C.)
This year is M.D. 50 (Modern Date, Modern Day?)
Option 1 doesn't suck as much as you make it out to. The system without an update will still dock the satellite at the right time. You tell it, dock at 1435732692.543, and it will dock at 1435732692.543. If you try to transmit the time in another format that needs to be converted, then you run into problems.
Docking things in space isn't just a function you execute in a computer, it wouldn't just work it out.
It's been a few years. Do we know why now?