Leap Second To Be Added Dec 31, 2008 255
ammorris writes "Don't be the laughingstock of your friends when you shout 'Happy New Years' a second too early ... The International Earth Rotation and Reference Systems Service has announced that a leap second will be added on December 31, 2008 at 23h 59m 60s, meaning that this year will be exactly one second longer. The last leap second occurred Dec 31, 2005; they are added due to fluctuations in the rotational speed of the earth. You can read all about leap seconds on Wikipedia."
Second! (Score:5, Funny)
3... 2... 1... (Score:3, Funny)
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Re:Second! (Score:4, Insightful)
It's like raising a puppy. The worst punishment possible is to pay no attention.
The Internet is full of idiots/trolls/criminals/mentally ill. Banning is not a solution. After banning they just start to hide and use a proxy.
Ignoring is the best way.
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That's what mods are for. Apparently, however, they enjoyed the joke!
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Gee, thanks for the notice (Score:4, Funny)
Uhh, wouldn't it be nice if we were given a little bit more of a warning? Say, something like, oh a week?
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Re:Gee, thanks for the notice (Score:5, Informative)
The bulletin is dated 4 July 2008, it's just the Slashdot article that's late. Or even, just on time as a reminder.
Re:Gee, thanks for the notice (Score:5, Insightful)
Re:Gee, thanks for the notice (Score:5, Funny)
know about what?
I dont even read the Summary, so what the heck are we even talking about?
Complication? (Score:3, Insightful)
Leap seconds get added all the time. They can't be predicted years in advance. http://en.wikipedia.org/wiki/Leap_second [wikipedia.org]
If you are running NTP or have a radio-controlled lock they will handle this just fine.
If you have a real atomic clock you don't care, atomic clocks never get reset.
Otherwise, you have a couple days to fix your bugs.
Re:Gee, thanks for the notice (Score:5, Interesting)
Uhh, wouldn't it be nice if we were given a little bit more of a warning? Say, something like, oh a week?
You may laugh, but I work in Air Traffic Control. We rely on absolutely precise timing in a system distributed over 1000s of kilometres. Many components can be marked as non-functional by the system if they appear to have an incorrect clock.
Every time we add a leap second we get issues raised. I have to say it is a real PITA.
Re:Gee, thanks for the notice (Score:5, Informative)
Re:Gee, thanks for the notice (Score:5, Informative)
Re:Gee, thanks for the notice (Score:5, Interesting)
Some people mistakenly think NTP is a silver bullet for handling timing issues.
NTP is great for keeping consistent time *over time*. It is horrible for handling stuff like a leap second, it simply takes too long.
Some systems use GPS, some use IRIG-B and some use NTP. Some handle leap seconds and some don't.
If you work with telemetry, like I do, you need time to be 100% correct all the time or else the data is worthless. This leap second is actually causing NASa and other space agencies to not do satellite supports close to midnight on new-years eve UTC.
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Re:Gee, thanks for the notice (Score:5, Informative)
"Slew the time"? What system does that? According to the following page, the NTP server announces the leap second in advanced, and "well-behaved" kernels count the extra second like they are supposed to; i.e. there is no slewing:
http://www.cis.udel.edu/~mills/leap.html [udel.edu]
Re:Gee, thanks for the notice (Score:5, Interesting)
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If you need microsecond accuracy you have your timing and distribution systems, you pay attention to the bulletins, and you program this particular event (which your timer should have capacity for) back in July which is when this was first announced.
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You mean that in a critical field-of-work a system that fails more often than "doesn't work on leap days" gets past the acceptance tests?
I now understand where the pressure to remove leap seconds comes from. From the idiots that can't specify systems that handle them correctly.
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Excuse me? If everybody supports leap days, and time needs to be accurately kept across systems, then all systems should simply implement leap seconds.
It is not acceptable if some software implements the leap-day as the first day of a leap year. It is only acceptable as the last day of february.
So when a leap second comes about, everybody leaps a second at the same time, and no noise is introduced.
If clocks slew at different rates, they need to be corrected for anyway. So either you run public NTP which wil
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It can [udel.edu].
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It never allows time to just jump. It always slews the clock. My ubuntu desktop system at work took two weeks to slew the time by a couple of hours.
From "man ntpd":
Normally, the time is slewed if the offset is less than the step threshold, which is 128 ms by default, and stepped if above the threshold.
(That was from an Ubuntu 8.04 system, but it's consistent with my experience over the last decade+).
If your machine slewed a two-hour correction, then something is strange about your configuration.
Also from the man page, the slew rate of typical kernels is limited to 0.5 ms/s, so a two-hour slew would take 167 days, not two weeks.
Re:Gee, thanks for the notice (Score:5, Informative)
The NTP daemon is normally used to interface with GPS clocks and to distribute time around a LAN. It never allows time to just jump. It always slews the clock.
This, of course, is wrong.
First, by default it steps the time on startup, with a default limit of 1000 seconds offset, but you can disable this limit.
Second, after startup, by default it slews the time unless the offset is greater than 128ms, in which case it steps the time. The 128ms value is configurable via the "tinker" command, but it is not recommended that it be changed.
Re:Gee, thanks for the notice (Score:5, Interesting)
Yeah, we had problems in Google with these too; we have large networks of machines that used to use multiple different NTP servers (for resilience). Turns out not all NTP servers implemented leap seconds the same way, and many cluster based applications get upset when they aren't synchronized to within 100ms.
Now, we run a dry-run of a fake leap-second with all software a few weeks before the leap-second failover. It's the only way to be 100% sure that applications changed since the last leap second won't have problems. Though, most unittest frameworks now have the ability to implement second skewing, since the suffering caused by the 2005 leap second.
The main problem is that the POSIX description of how to do a leap second is retarded; you basically go from 00:00:00 to 00:00:59, some apps also get upset when they see the same time twice.
John
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(Score:5, leaks company procedures and shortcomings)
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Turns out not all NTP servers implemented leap seconds the same way, and many cluster based applications get upset when they aren't synchronized to within 100ms.
Given that most computers have utterly horrible tickers (irony: a $15 Timex watch keeps much better time than this $4,000 server), can you usually expect that much precision?
why rely on hh/mm/ss instead of millis elapsed... (Score:3, Insightful)
Uhh, wouldn't it be nice if we were given a little bit more of a warning? Say, something like, oh a week?
You may laugh, but I work in Air Traffic Control. We rely on absolutely precise timing in a system distributed over 1000s of kilometres. Many components can be marked as non-functional by the system if they appear to have an incorrect clock.
Every time we add a leap second we get issues raised. I have to say it is a real PITA.
What I find baffling is that architects/developers working in such a life-critical field managed to conceive application relying on days/minutes which are NOT fixed values. (a minute can have 59 or 61 seconds while a day can have 23 or 25 hours).
That said, the clock of a Un*x system is usually calibrated in milliseconds since the epoch and this has absolutely zero, nada, zilch, nothing to do with leaps seconds. The fact that we decide that 31 dec 2008 with have a 61 seconds minute change *nothing* to the c
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Is that true?
I know that this is how timezones, DST and leap years are handled, but are leap seconds handled like this too?
In other words, if I ask a Un*x system about the number of seconds since epoch for 2008-12-31 23:59:5
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Sorry, but that is exactly the point. Unix time was given as an example of a correct time implemention using a fixed base, but as far as I can see, it does not use a fixed base in this particular case. If it did, ntp deamons on unix systems would not have to slew or jump the kernel clock when a leap second is inserted.
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Which leaves two problems to be solved in a practical implementation:
1. You have to use GPS receivers which actually shows true GPS time, not GPS time corrected to UTC.
As someone has stated in another part of the discussion, GPS receivers will receive GPS time from the satellites, but they also receive a UTC correction which is calculated into the ti
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Wow, that's such a crappy definition. It clearly states a linear time scale, while it is not actually linear.
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You may laugh, but I work in Air Traffic Control. We rely on absolutely precise timing in a system distributed over 1000s of kilometres. Many components can be marked as non-functional by the system if they appear to have an incorrect clock.
Every time we add a leap second we get issues raised. I have to say it is a real PITA.
Leap seconds were invented in 1972. You mean your systems didn't get leap second support addressed when you got your Y2K fixes?
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The summary gives the impression that they figured this out today. The announcement is just a reminder and a PR magnet.
This has been known for quite some time and is significant for some industries (like my field of work; satellite telemetry).
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Uhh, wouldn't it be nice if we were given a little bit more of a warning? Say, something like, oh a week?
Yeah! This totally f*cks my schedule. One second totally ruins New Years for me.
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Only if you celebrate New Year's at 23:59 GMT. All other time zones will have New Year's take place exactly on schedule to the second including Times Square in New York.
Call me geeky, but isn't that the only true way to celebrate it? That's when all my servers are celebrating it...
2008?!! (Score:5, Funny)
Gah! I can't take another second of this!
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I just think it's about time.
Re:2008?!! (Score:5, Funny)
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I second that!
legally speaking, it's the first leap for the US (Score:5, Informative)
Re:legally speaking, it's the first leap for the U (Score:5, Informative)
Yes, yes, that's Nix vs Hedden and it was ruling by the U.S. Supreme Court in 1893. The court ruled that in the common parlance of the time a tomato was seen to be a vegetable and not a "fruit of the vine", working from the assumption that most people at it for a main course instead of a dessert. I think that if you were going to pick up on the ridiculous nature of the case you'd focus on the reason behind the court case — that taxes needed to be paid on imported vegetables and yet not on imported fruit.
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Leap days and leap seconds serve different purposes.
Leap days are because our definition of a day (and thus a year) are not exact. A year is actually ~365.25 days, so we add an extra day every 4 years to compensate.
Leap seconds are needed as there's another small random variance in the length of a day (The mean solar day lengthens by about 1.7ms per century, due to slowing of the earth's rotation), so we occasionally need to add a second to keep us in sync with astronomical time.
Longer, or shorter? (Score:4, Informative)
"Don't be the laughingstock of your friends when you shout 'Happy New Years' a second too early ... this year will be exactly one second longer."
So... wouldnt we be shouting it one second later than everyone else?
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That's UTC (Score:5, Informative)
You have a chance! (Score:2, Funny)
If you messed up in 2008 you still have an extra second to make good.
DON'T WASTE THIS GOLDEN OPPORTUNITY!
I'll have to mention this to HR... (Score:5, Funny)
Re:I'll have to mention this to HR... (Score:5, Funny)
Wha ...? (Score:5, Funny)
Wait just a second, now! I ... oh.
Damn Bush (Score:5, Funny)
Bush will do anything to remain president just a little longer.
Excellent news for my sex life (Score:5, Funny)
OK, just kidding - I am a
Re:Excellent news for my sex life (Score:5, Funny)
You'll have to hope for a leap-inch or two before that happens
While we're at nitpicking (Score:3, Interesting)
What timezone will it be added to at midnight?
Yes, I know, it is not nitpicking because it's nontrivial for certain high precision science projects... even though I couldn't think of one right now, but it's gonna be quite important for someone.
But just to add a joke: Effin' great, as if daylight saving didn't put enough stress on the mechanics of my clocks!
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Considering the people here start to fire off their rockets any time between 6pm and 6am that special nite, I doubt the second really matters either way...
Added When (Score:2)
The International Earth Rotation and Reference Systems Service has announced that a leap second will be added on December 31, 2008 [CC] at 23h 59m 60s
My understanding is that the last 60 seconds of the year will be 1/60th of a second longer. Or will my GPS actually read "23h 59m 59s" twice?
Re:Added When (Score:5, Informative)
The length of the second doesn't change. An extra second is added. I work with precision timing systems where this is an issue.
The sequence is:
23:59:59 UTC
23:59:60 UTC
00:00:00 UTC
00:00:01 UTC
That means that the valid range for seconds is 0..60 and it is possible to have 61 seconds in a minute. You need to know this if you are using a programming language with range checks.
GPS uses its own time scale that isn't affected by leap seconds.
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maybe we should use stardates? they just sound so cool
*read in a Picard voice* ... this Data guy is really freaking me out lately ...
stardate 48182.647... captains log supplemental... #1 is humping my leg... off boy off!
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I don't doubt that it does that internally, but GPS receivers usually put a timestamp on the position. How is this timestamp affected?
Will a GPS receiver continue to convert the internal time to UTC following an outdated algorithm which is hardcoded into the receiver, or is the conversion algorithm part of the data received from the satellites?
In other words: Can we trust the time from a GPS receiver, or will two receivers show a difference o
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Along with that time, there is a broadcast of the current offset between GPS time and the current UTC time. This offset goes up by 1 on every leap second since the GPS system first went live.
So as long as the receiver is getting all the GPS broadcasts, it will always know what the correct UTC time is.
"Happy first bug of the new year!" (Score:2)
That means that the valid range for seconds is 0..60 and it is possible to have 61 seconds in a minute. You need to know this if you are using a programming language with range checks.
Oh, shit.
Well, at least I'll know what I'll be doing on my first day of work next year.
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Will windows automatically adjust my clock for me? (Score:4, Funny)
Or, is that only in the vista ultimate edition?
Nah (Score:2, Funny)
No big d.......eal.
Happy New..... (Score:2)
Second?
Fluctuations? (Score:3, Interesting)
Re:Fluctuations? (Score:5, Informative)
I'm sorry? Fluctuations in the rotation of the earth? You mean the earth is accelerating and breaking?
Yes, that's exactly what we mean (well, "braking" rather than "breaking"). The earth does not have a constant angular velocity. To conserve angular momentum, as the mass distribution of the earth changes (e.g. due to glacial rebound), the spinning of the earth speeds up and slows down. It also slows down a little due to tidal braking. So a "day", as measured by the rotation of the earth relative to the fixed stars, is not exactly 86400 seconds. It's generally a little more, around 86400.001 seconds at present, and it varies from day to day and from year to year. Now that civil time (UTC) is kept with atomic clocks, this is a genuine problem. Leap seconds are introduced to keep UTC close to UT1 (astronomical time).
It has nothing to do with the fact that a rotation around the sun is not exactly 365.25 rotations around our own axis? hmm...
That's right. Leap seconds have nothing whatsoever to do with that. They don't affect the calendar. That's what leap days are for. Leap days keep the calendar in sync with the seasons (by setting the average calendar year length to 365.2425 days, very close to the vernal equinox year which is currently 365.242374 days).
Re:Fluctuations? (Score:5, Informative)
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Pun intended?
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Re:Fluctuations? (Score:4, Informative)
There is a drift, and there are fluctuations.
Regarding the drift: The day length is getting gradually longer by about 1.7 milliseconds every century (+2.3ms due to tidal braking, -0.6ms due to glacial rebound). In about 1820 the day was 86400 seconds; now it is longer than that. In a thousand years, the day will be about 86400.017 seconds, and we will need a leap second every couple of months.
[Note: I am simplifying a little here for the sake of clarity by ignoring the difference between a solar day and the stellar and sidereal days, which are about 4 minutes shorter].
Regarding the fluctuations: There are fluctuations of the earth's angular velocity on many timescales. It fluctuates with weather, with the seasons, and with major events on the surface (e.g. a dam creating a new reservoir) and in the earth's crust (e.g. an earthquake or major volcanic eruption) and deeper interior (e.g. we don't really know). All these events are minor rearrangements of the mass of the earth, which change its moment of inertia. Conservation of angular momentum dictates that the angular velocity must change, and it does. Of course the earth isn't a rigid body and that complicates all this. Learn about Geodesy if you want to know more.
In the 1990s the day length was approximately 86400.003 seconds, so we needed a leap second every year. For poorly-understood reasons (possibly some sort of deep mantle activity), the earth's rotation speeded up around the year 2000, and for a while the day length was about 86400.0004 seconds. Now it is slower again, about 86400.001 seconds. These changes all come under the "fluctuations" heading.
There is an organisation called the IERS [iers.org] - International Earth Rotation and reference Systems Service - which collects measurements of all this stuff to very high accuracy and produces all sorts of reports, bulletins, data sets, etc etc.
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However, the rotation around the Earths axis isn't all that smooth. It indeed accelerates and breakes due to tidal movements, atmosferic influences and interference with the Earths polar wobble.
The day-to-day difference can be as high as a few seconds, but averages taken over a long(ish) period are very stable. It has to be, conservation of momentum-wise.
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It has nothing to do with the fact that a rotation around the sun is not exactly 365.25 rotations around our own axis?
No, it does not. Leap days are about keeping the calendar in sync with the seasons. Leap seconds are about keeping the clock in sync with the rotation of the earth. These are two different components of motion, and they are handled with different measures.
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If it were, there would be 364.25 solar days in a year.
rj
"Length-of-day" is a serious geoscience parameter (Score:2)
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There's also a theorized seasonal component caused by sap rising and leaves growing in trees in alternate hemispheres, but that's pretty well down in the noise.
rj
Leap second at UTC, not Local midnight! (Score:5, Informative)
The UTC second 60 gets added at midnight only at those locations where UTC == local time, i.e. places like England.
For us in the rest of Europe, the leap second will be added an hour after local midnight, i.e. at 01:00:60 CET.
Terje
Re:Leap second at UTC, not Local midnight! (Score:4, Informative)
00:59:60 CET, you mean.
And there are other timezones besides Greenwich Mean Time [wikipedia.org] and Central European Time [wikipedia.org] in Europe too: Eastern European Time [wikipedia.org], Moscou Time [wikipedia.org] and even a smattering of Samara Time [wikipedia.org] and Yekaterinburg Time [wikipedia.org].
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Oops! Mea Culpa.
You're totally right, and I really should know better. :-)
Terje
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So, most of you Europeans (and Asians & Aussies) will be adding your second in 2009. Us Americans have to suffer through 2008 that extra second. :P
The Barnicle says (Score:2)
Leisure-suit up! This is going to be legend... wait for it...
The older you get.... (Score:2)
....the faster time flies by...
But damn'it... ya all don't have to help it.
The last second of the day (Score:2, Funny)
To be subtle, they added the leap second to the one time in the entire year when everyone (at least in that time zone) is watching the clock and counting along with it.
IERS (Score:2)
Damn. I've been following the International Earth Rotation and Reference Systems Service (IERS) emails for years and this one managed to slip into my spam filter. Thanks slashdot! for making sure I didn't miss it this year!!!
(A great bonding moment with my father was counting along to 61 with the atomic clock signal on the short wave while sitting by the sundial at the local science museum...)
Leap leap... (Score:5, Informative)
No it isn't. It's a 86401 seconds longer. Than last year. Or 86400 longer than the previous leap-second-year 2005. Oh, yeah, it's exactly 1 second longer than 2004 and 1996.
I confess enjoying myself as a time nazi. Should not forget to count february 29th...
Re:Leap leap... (Score:5, Informative)
I'd mod you up if I could. Instead, I'll add these bits of trivia:
The last time we had a leap second and a leap year was in 1992. The last time we had it on December 31 was 1976.
The only time we had two leap seconds (June 30 23:59:60 and December 31 23:59:60) was on leap year 1972, the first year leap seconds were applied, and making 1972 the longest year.
And in that one second... (Score:2)
Let's be done with '08 already - let's add that extra second to a good year
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Re:how will my computer know (Score:4, Interesting)
I don't suppose this leap second has been encoded into timezone information like daylight saving time has been.
So I would just run ntpd and expect the clock to step 1 second.
At second thought, I would expect ntpd to gradually slew system time since 1s is too small an offset to step the clock at once. Maybe it would be better to stop ntpd and restart it with -g or even delete its drift file since this second is not an error of the system clock but artificially introduced? Anyone know?
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NTP does include leap seconds if your timeserver knows about it, which all good timeservers should do. It shouldn't show up as a slew if ntpd behaves properly, it's a distinct step. Have a look at your logs after midnight and see if it's there.