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Leap Second At The End of 2005 269

Posted by CmdrTaco
from the correct-your-watches-immediately dept.
Ruff_ilb writes "Because of the discrepency between an ephemeris second (the fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time) and the second of atomic time (the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom), we're left with more than leap years. In order to ensure that the the atomic time and civil stay coordinated, "Civil time is occasionally adjusted by one second increments to ensure that the difference between a uniform time scale defined by atomic clocks does not differ from the Earth's rotational time by more than 0.9 seconds."" And Happy New Years everyone ;)
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Leap Second At The End of 2005

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  • by Chemisor (97276) on Sunday January 01, 2006 @11:53AM (#14374340)
    And, of course, I already used it to read Slashdot. Oh, darn...
  • by rolypolyman (933130) on Sunday January 01, 2006 @11:54AM (#14374346)
    If you watch carefully for that leap second, you can do a freeze-frame flying kick like in The Matrix.
  • by Anonymous Coward on Sunday January 01, 2006 @11:56AM (#14374355)
    Adjusting the clock is of course the easy way to solve the mismatch between our ideal time and earth's rotation.

    Real engineering solution would involve changing earth's rotation speed to match the clock. Any takers?
    • by MyLongNickName (822545) on Sunday January 01, 2006 @12:07PM (#14374410) Journal
      Adjusting the clock is of course the easy way to solve the mismatch between our ideal time and earth's rotation

      Oh yeah? It took me about ten minutes to adjust all the clocks in my house due to the damn leap second. Multiply this by the 100 million households in the nation, and we have a very serious issue here.

      I demand that George Bush pull us out of whatever God forsaken U.N. treaty that got us into this mess.
    • My clock is set by radio and has no manual adjust, you insensitive clod!
    • Well, we just need to reduce Earth's momentum of inertia. According to the law of conservation of angular momentum it will make Earth rotate faster.

      You can try this on yourself: sit on a swivel chair and start spinning with your hands held apart, then quickly pull your hands close to your body - you should start rotate faster.

      I think if we level all mountain ranges and melt both ice caps it should be enough to make Earth spin faster enough to compensate for this leap second.
      • Re:The hard way (Score:3, Insightful)

        by jc42 (318812)
        I think if we level all mountain ranges and melt both ice caps it should be enough to make Earth spin faster enough to compensate for this leap second

        Um, if you melt the ice caps, won't the water spread itself out through the oceans? This will, on the average, make the molecules move away from the axis, thus slowing the planet's rotation.

        What you want to do is pile mass up close to the axis, i.e., at the poles. With water, you'd need to precipitate it out at the poles. This isn't what we're doing, though
    • Is the earth really slowing down, or is it that our electronic clocks are being affected by something else? If you go back over the centuries, you will notice the speed of light has been measured at different speeds. Hmmmm, I wonder.
    • I'm afraid it would have to be an ongoing thing; the Earth is slowing down due to tidal braking, and as it's unpredictable enough already just figuring out when to give our planet a nudge would be hard enough. Good luck!
  • countdown (Score:3, Funny)

    by Anonymous Coward on Sunday January 01, 2006 @11:56AM (#14374359)
    10,9,8,7,6,5,4,3,2,1,0,-1

    -Sj53
  • Those with updated (don't know from when) libc or equivalent automatically encountered the leap second at midnight. Even if you didn't, you'll still sync back up with an NTP server eventually (I'd hope).
    • hopefully you don't mean that literally, or it's a bug (although an admittedly minor one); the change didn't happen at midnight for most of the world. for example, it was 19:00:60 in EST.
  • oh great (Score:2, Funny)

    by BushCheney08 (917605)
    Great! Now I hafta go around the house and adjust all the clocks again...
  • Damn! (Score:4, Funny)

    by Black Parrot (19622) * on Sunday January 01, 2006 @12:00PM (#14374368)
    Now my clock is 121 seconds off, instead of just 120.

    Thank goodness I didn't bother setting the VCR clock after the last thunderstorm.
  • by Dr. Zowie (109983) <slashdot@defPARISorest.org minus city> on Sunday January 01, 2006 @12:02PM (#14374379)
    The NTP [slashdot.org] protocol that all of us cool kids use to synchronize our computers' clocks has a fundamental flaw -- the NTP time is tied to UTC [wikipedia.org], but contains no leap seconds at all, more like TAI [wikipedia.org], the atomic time standard. When there's a leap second, the system's solution is to ignore it.

    So, as of today, any time stamp you have made using NTP, ever, has been retroactively displaced by one second. Intervals that included midnight (UTC) last night are all too short by one second.

    This may not be a problem for handling your calendar appointments, but it can muck up all kinds of scientific applications that require high precision.

    • by thehickcoder (620326) on Sunday January 01, 2006 @12:17PM (#14374448) Homepage
      Actually, if you where doing high precision scientific applications, it seems this type of behavior would be preferred. Because of the leap second there was not 2 seconds between 11:59:59 and 12:00:01 last night. So, using the NTP behavior if I want a timestamp that was exactly 10000000 seconds ago, I get one that represents 10000000 actually elapsed seconds.

      Just because everybody agrees to change their clocks doesn't mean time actually slows down or speeds up.
      • There's alternative scientific research which hints that the speed of light is variable. Maybe the earth isn't slowing down. Maybe our atomic clocks are just getting faster.
      • by Dr. Zowie (109983) <slashdot@defPARISorest.org minus city> on Sunday January 01, 2006 @01:17PM (#14374684)
        Hmmm... Maybe I wasn't clear to start with. If (using my handy atomic clock) I made an NTP timestamp at precisely 11:00 pm UTC yesterday, and another NTP timestamp at precisely 11:00 pm UTC today, those two timestamps would differ by exactly 24 hours, although the two UTC times are 24 hours and one second apart. That is an error. T

        he error is carried by the fact that NTP stays synchronized to UTC in the present, but the past is "free floating". If, today, I convert my previous NTP timestamp back to UTC I will find that it occurred at 11:00:01pm yesterday rather than 11:00:00, the time that I actually made it. That's because NTP counts offsets from the present moment, assuming that UTC behaves like TAI.

        • According to the FAQ on the NTP homepage [ntp.org] "NTP uses UTC as reference time"

          Further down there is a discussion of how leap seconds are handled. I was curious so I checked my computer clock (which is synced using NTP) against my alarm clock (which uses the radio signal from the MSF [npl.co.uk] service and they are the same. So it seems that NTP must have observed leap seconds contrary to your original post.
    • NTP does include support for leap seconds - there are bits that can be set by the primary time source to indicate that a leap second will occur soon. NTP isn't a time source itself - it's a protocol for transferring time. You can use whatever time source you want for NTP - it's up to the time source to set the bits if desired.

      NTP is intended for synchronising computers together (useful for servers). It is not intended to provide a highly accurate time signal for scientific applications. If you need that
      • ...the atomic clocks onboard the satellites.

        That leads to an interesting question: the satellites are in reduced gravity, which increases the rate at which time passes, and moving faster than we do here on the ground which lowers it. I doubt that the two effects cancel out completely, as they're not moving that fast. Is there a correction for this included in their software, or is GPS time really a little fast compared to what we have on the ground? Anybody out there know?

    • by Floody (153869) on Sunday January 01, 2006 @03:57PM (#14375329)
      The NTP protocol that all of us cool kids use to synchronize our computers' clocks has a fundamental flaw -- the NTP time is tied to UTC, but contains no leap seconds at all, more like TAI, the atomic time standard. When there's a leap second, the system's solution is to ignore it.

      So, as of today, any time stamp you have made using NTP, ever, has been retroactively displaced by one second. Intervals that included midnight (UTC) last night are all too short by one second.

      This may not be a problem for handling your calendar appointments, but it can muck up all kinds of scientific applications that require high precision.


      You are confusing transport with content. NTP, by itself, has no inherent concept of leap-seconds, leap-years or any other sort of temporal leapage; it simply provides a way to statistically analyze time sources, account for latency, jitter and dispersion and keep a local clock as closely synced as possible to one or more remote clocks. When making adjustments to the local clock, it is careful to not introduce large amounts of skew which might wreak havoc on time sensitive running processes Iinstead it will slowly "bump" the clock towards what it currently thinks is the most accurate time.

      To make NTP useful, of course, it must be provided with one or more ultimately trusted authoritative time source (these can be stratified [stratums] in terms of network closeness to the original time reference). As you noted, major reference clocks on the net use a UTC time source, which makes more sense for common applications than TAI, as non-scientific-clocks world-wide are based on UTC.

      When the leap second was added at the beginning of this year (this morning -- or perhaps the very end of last year), the UTC was simply adjusted by one second. stratum 1 NTP servers which are directly hardwired to reference clocks (ultimately, that means atomic clocks), adjusted by the UTC-TAI offset, trust their reference clocks above all else; thus when they saw the UTC adjustment they simply assumed that their local cpu clock was off and began adjusting it accordingly (from the reference frame of the NTP timescale, time "stood still" for one second). Simultanously, any new broadcasts or query-responses sent out on a network interface used the newly offset time. Downstream NTP daemons would make a similar conclusion; that their local clock had drifted one second off and should be slowly adjusted towards the correct time.

      The net effect is that if you were to view NTP as a continous set of incrementing ticks beginning on 0h Jan 1, 1900 GMT (UTC origin is TAI -10s 0h Jan 1, 1972, and thus technically is meaningless for timescales that originate prior to the epoch), historical timecodes are effectively lost on each update where a leap second has been inserted, however the current timecode is in sync with UTC.

      Sensitive scientific applications will likely simply avoid the UTC offset completely and use a direct TAI reference clock.

  • Yeah! - Mandatory overtime - I get time and a half! - Oh wait.......nevermind
  • time.gov (Score:5, Informative)

    by srblackbird (569638) on Sunday January 01, 2006 @12:04PM (#14374392) Homepage
    I watched the time at Time.gov: 23:59:56 (UTC) =>23:59:57=>23:59:58=>23:59:59=>23:59:60!=>00:00:0 0
    It was Amazing! This was the first time for me... *remebers where I was at that moment
  • So during the correction of the clocks and the extra second being added, what did you do? Did you ponder world peace? The latest 0 day exploits for Windows? Where Microsoft is going with the .NET platform with version 2.0? Or were most of you transfixed on Times Square watching the ball drop getting close to someone you love?
  • old news (Score:5, Funny)

    by Viriatus (886319) on Sunday January 01, 2006 @12:08PM (#14374411)
    Old news, from last year.
    • Since the leap second was added at midnight UTC, it was already noon back on the international dateline. So the adjustment was 1/2 way through the first day of the year.
  • oh, shit. (Score:2, Funny)

    by CAIMLAS (41445)
    Oh, shit. I've got to reset my goddamn clock again.
  • by Jonathan McDowell (515872) on Sunday January 01, 2006 @12:25PM (#14374478) Homepage
    Original poster is slightly wrong - it's not the length of the 1900 ephemeris second,
    it's the fact that the Earth, like all of us, is getting older and slowing down, so that
    the 2005 "Earth rotation" second (i.e. 1/86400 of one spin of the Earth) is longer than
    the 1900 equivalent and longer than the atomic time (SI) second. Instead of changing
    the length of the second, it is currently deemed less painful to keep using the old
    length and stick in an extra second every now and again.

    Since this depends on the slop of the Earth's interior, it's not a fully regular and predictable thing - we might even have to remove a second one year.
    • It is worth noting that those "leap seconds" amuse only some people. People who work on systems that can't afford a 1 second discontinuity (such as the GPS system) use a continuous counting of the SI second.

      http://www.leapsecond.com/java/gpsclock.htm [leapsecond.com]
      • Right. If you want a timescale that guarantees that it's dark at midnight, you use UTC, locked to the Earth's rotation. If you want a timescale which guarantees a simple calculation of the elapsed time between two time stamps, use TAI or TT or GPS time or another timescale that's linked to atomic time or proper time in some rest frame. The scientific community provides all the different timescales that you might want, all of them within a couple of minutes of being GMT. The Earth-locked one makes sense for
      • The discontinuity is only in the assignment of seconds of linear time (i.e., the number of seconds that have elapsed since some reference) to days and time of day. For purposes like GPS, where you don't care at all about making the time relevant to humans, the linear time is perfectly sufficient, and there aren't leap seconds or leap year days because those concepts are only relevant to the alignment of units larger than seconds. That site is a bit misleading, actually. GPS time doesn't use an hour:minute:
    • This is very true.

      To within about one part in 1.E12 the ephemeris second is identical to the SI second defined by the cesium resonance. In 1977 the length of the second of TAI was changed [ucolick.org] so as to conform better with the preferred definition of the SI second. Before 1977 TAI and UTC ticked faster than they do now. Astronomers did not object to the change in rate of TAI because it was within the uncertainty of the original definition of the ephemeris second.

  • Great (Score:5, Funny)

    by the eric conspiracy (20178) on Sunday January 01, 2006 @12:31PM (#14374497)
    Gotta love those long weekends!

  • There was a January 0 in year 1900? Hmm found no mention of it here [wikipedia.org].

    - Thomas;
    • Have a look at an old ephemeris and see the large numbers of tabulations of quantities with respect to date. For the sake of ease of typesetting it was commonplace to have tables with dates such as January 0, 5, 10, 15, 20, 25, 30, and 35. That avoided the need to redundantly set more lead into the matrix for the name of the month o nevery single line of the tables. In the case of tables being interpreted by humans there was no expectation of raising some sort of input exception because in the full conte
  • The clock problems (Score:4, Interesting)

    by Antony-Kyre (807195) on Sunday January 01, 2006 @12:48PM (#14374557)
    Did anyone notice the atomic clock problems that happened when the leap second occurred? Some atomic clocks were different than others. If I am not mistaken, and I don't believe I am, the leap second occurred at 23:59:60 UTC (yes, I typed that in correctly). I also flipped back and forth between like ABC and NBC, Pacific Time, and notice they were like 3 seconds or so different in their countdown clocks. What is up with that?
    • by DAldredge (2353)
      That may have been caused by different lenghts of time delay. not all networks use the same amount of time delay on their live feeds.
      • And I thought atomic clock servers were suppose to be accurate. I guess I was wrong. I manually used a program to check my computer time against atomic clock servers. Some servers didn't recognize the leap second, and I really thought they were suppose to be accurate.
    • I also flipped back and forth between like ABC and NBC, Pacific Time, and notice they were like 3 seconds or so different in their countdown clocks. What is up with that?

      I was watching CNN and they had a couple seconds difference between their on screen countdown and the Times Square Coke-sign countdown. It kind of scrapped the fun of counting down to 2006, CNN was allready at 0 when Times Square had 4 seconds left.

      Yeah, I'm a dork, having my new year's fun scrapped by a 4 seconds discrepancy.

    • by Hillman (137883)
      Some networks use a time delay to filter out profanities. Also it might be because the feed you're watching goes thru a sat link before reaching your affiliate.
    • by PPGMD (679725) on Sunday January 01, 2006 @03:03PM (#14375140) Journal
      Sat delays along with buffer so they can dump profanity can build up the time difference.

      Last year during the Superbowl it was noticeable at my house, I had 3 TVs tuned to the game, 2 via DirecTV and another using rabbit ears, the over the air broadcast was easily 2-3 seconds ahead of the DTV broadcast. This is one of the reasons that the Sport Betting Houses that allow betting up until play completion don't allow cellphones, because you could have someone watching via a faster source or at the game itself, feeding you what's going to happen.

    • by isorox (205688)
      We (A national UK broadcaster) had a countdown clock (2 identical computers). It was linked from the corp's central ntp server (in turn via GPS), but generally it's a PC clock. Normal broadcast equipment runs off a time code generator that's slaved to GPS.

      It wasn't far off the pips on radio 4 analog (ignore big ben etc) in the gallery.

      After leaving the gallery, it travels down to one CTA, then another, then another, then gets split, and is sent via seperate routes to the main transmitter in Crystal Palace.
    • I also flipped back and forth between like ABC and NBC, Pacific Time, and notice they were like 3 seconds or so different in their countdown clocks. What is up with that?


      Differing amounts of broadcast time delay?

  • Rob, we all saw that coming a few days ago. But /now/ it's important to *you*. If you'd just stop with the babymaking attempts, playing with your new Legos and ignoring dupes you could start working on the reply for the 1,000,000 Slashdot account.
  • by Fishstick (150821) on Sunday January 01, 2006 @01:17PM (#14374680) Journal
    "This year's leap second is an assault on the American public," says commentator Bill O'Reilly. "The reason the leap second is even being proposed is because of America Haters, because of Iraqi hate mongers, and let's be honest, Shiites. Why would you add a second to the year unless you're an anti-American hate monger?
    I remember liberals at a party saying, 'let's add a second to the year' and I was the only one who spoke up against it. Why would they want to add a second to the year? Because it gives them a second longer to hate Bush.

    "Look, look, look, look. A leap second is a denial of everything American, of everything good, of everything moral. They're saying we need this second because the earth rotates on its axis and revolves around the earth, well this is the no spin zone. So we don't need a leap second. Though I would rather have a leap second than some of these hate-mongers who go around hating even their own ideas! They need to hate their own ideas so much that you have many liberals proposing the leap second, which is an idea that they hate, yet, they propose.

    "I am so so so so upset with these people, who actually believe their ideas, yet, I have no hate in my heart. I am a simple guy, who only has my own true beliefs and a few products that are my cornerstone to fight against the leap second poobah. Let me say it aloud: Leap Second, leap second, leap second. Doesn't it sound ugly?

    "Please, don't let these Darwinian leap-seconders, who believe that the planets revolve around the sun, who believe that rocks are sedimentary, igneous and stalactites, who are innocent dim-wit believers in a faith bordering on hating everything religious like trees and fruitcake, yet, who don't believe in John 7:12:45:67:89, have their say.

    "But you know what I love? Dialogue. Rational dialogue which allows me to say that aliens from a Iraqi loving planet want to abolish Christmas by adding a leap second to the Darwinian anti-God year. Dialogue is what keeps the American system God-loving and anti non-God. It also keeps the anti-God loving non-Iraqi loving insurgent deniers able to voice their hideous so-called opinions over the American loving tolerant airways. And now let's take some calls."

    Steve Martin [huffingtonpost.com]
  • Are they also adjusting the clock because the Dec 2004 earthquake and tsunami caused a small change in the rotation speed of the earth? I believe it caused the rotation to last a few miliseconds longer for that day. There some info at the NOVA site on pbs.org:
    http://www.pbs.org/wgbh/nova/tsunami/ask-050331.ht ml [pbs.org]
    (scroll down to the sixth question)
  • by BiggRanger (787488) <BiggRanger@nosPaM.tds.net> on Sunday January 01, 2006 @01:34PM (#14374741) Journal
    I did up a project on sourceforge.net a few years back to sync my computers with a GPS http://atomicgpsclock.sourceforge.net/ [sourceforge.net]. Below is a log of the activity, normally there is a +/- 0.016 or so second instability, but 18:59:59 EST (or 23:59:59 UTC) the Navy made a 1 second adjustment to the GPS system, and it's vibible in the log at the next scheduled sync (in bold)

    2005.12.31 18:33:49 00032 GPS Status - Tracking: 3D
    2005.12.31 18:43:27 00020 Offset: 000.016 Buffer: 13
    2005.12.31 18:43:27 00032 GPS Status - Tracking: 3D
    2005.12.31 18:43:49 00020 Offset: -000.031 Buffer: 13
    2005.12.31 18:43:49 00032 GPS Status - Tracking: 3D
    2005.12.31 18:45:15 00033 GPS Status - Tracking: No
    2005.12.31 18:45:34 00032 GPS Status - Tracking: 1D
    2005.12.31 18:46:48 00033 GPS Status - Tracking: No
    2005.12.31 18:46:52 00032 GPS Status - Tracking: 3D
    2005.12.31 19:01:43 00033 GPS Status - Tracking: No
    2005.12.31 19:01:55 00032 GPS Status - Tracking: 1D
    2005.12.31 19:03:45 00020 Offset: 001.016 Buffer: 13
    2005.12.31 19:03:45 00032 GPS Status - Tracking: 2D
    2005.12.31 19:13:45 00020 Offset: -000.016 Buffer: 13
    2005.12.31 19:13:45 00032 GPS Status - Tracking: 3D
    2005.12.31 19:23:43 00020 Offset: 000.000 Buffer: 13
    2005.12.31 19:23:43 00032 GPS Status - Tracking: 3D
    2005.12.31 19:33:43 00020 Offset: 000.000 Buffer: 13
    2005.12.31 19:33:43 00032 GPS Status - Tracking: 3D
    2005.12.31 19:43:30 00033 GPS Status - Tracking: No
    2005.12.31 19:43:40 00032 GPS Status - Tracking: 1D
    2005.12.31 19:53:41 00020 Offset: -000.031 Buffer: 13
    2005.12.31 19:53:41 00032 GPS Status - Tracking: 3D
    2005.12.31 20:03:39 00020 Offset: 000.000 Buffer: 13
    2005.12.31 20:03:39 00032 GPS Status - Tracking: 3D
  • I watched the time square ball drop from the west coast last night on TV -- nbc.

    of course, they printed "live" on the screen which was bs -- but did anyone else notice that the digital time on the screen and the seconds that the crowd were chanting down were 1 second off? obviously, I had way too little to drink this year to notice this, and no girl nearby to kiss.

    I'm wondering if maybe this was due to some clocks on 2005 time and some with more accurate accounting?

  • by Herve5 (879674) on Sunday January 01, 2006 @02:25PM (#14374975)
    I know a person in charge of geostationary satellite control, and she says this time adjustment will have imposed a large amount of satellite and ground station software updates.
    She added that because of this among many other updates, there have been a formal proposal by the US, some months ago, to change the rules and abandon any updating before there is a full day (!) of delay, but the proposal was refused.

    FYI, this 1-s correction is the first in 5 years, but there were 4 others in the previous 5 years.

    Waiting for one day would basically mean renouncing for some thousand years, or more probably, waiting for the next civilization to come :-)

    Hervé
  • No wonder I feel so well rested!
  • Double "the" in article:

    In order to ensure that the the atomic time ...
  • We all know what it was like for Y2K, and although nuclear bombs didn't fly out randomly from military bases across the world, now newspapers couldn't resist not to hype up the friggin' leap second again:

    http://www.suntimes.com/output/news/cst-nws-sec01. html [suntimes.com]

    Quote: "If you don't get all the clocks synchronized when the leap second occurs -- you could have potentially interesting effects," Chester said. "The Internet could stop working, cell phones could go out."

    YEA. SURE!
    • Even without leap seconds, it isn't unusual to see serious glitches in software when the time rolls over at the end of the year. I used to see it every year with software that predicted the orbits of satellites.
      • Looks like a piece of bad software to me ;)

        When you take complete date with seconds, minutes, days etc. etc. instead of just a timestamp, you have to implement much better logic that implements rolling of seconds into minutes, minutes into hours etc. then months into years, also account for leap years and so on.

        If the programmer got lazy and implemented logic up to months, you'll experience odd behaviour each new year's eve.

        But nothing is odd on new years eve, if you take the timestamp (timestamp is usually

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