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Earth Science

US DoD Poll On Leap Seconds 314

Posted by kdawson
from the great-leap-forward dept.
@10u8 writes "For time scales to leap, or not to leap, has been the question here before. The ITU-R will be considering leap seconds again in a few weeks. This week the USNO posted a survey about leap seconds by the US DoD. The issue has civil implications as well as technical ones, and there is a demonstrated way to respect the history, remove leaps from navigation and POSIX time, yet keep the sun overhead at noon."
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US DoD Poll On Leap Seconds

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  • by NoobixCube (1133473) on Monday September 08, 2008 @06:03PM (#24926697) Journal

    I thought we had leap years to take care of the discrepancy between our calendar and the actual orbit around the sun. Would a leap second even be made longer by any noticeable amount? What about sporting events? Someone who misses out on a world record by a tiny bit would complain that the record h older had more leap seconds in his race! (Okay, that one was a joke, but the rest I'm serious about)

    • by Anonymous Coward on Monday September 08, 2008 @06:05PM (#24926723)

      Compare absolute time vs relative time vs elapsed time vs hammer time...

    • Re: (Score:3, Insightful)

      by maxume (22995)

      The leap seconds do the same thing as the leap years (each leap day moves the calendar closer to the orbit, but not exactly to the orbit).

    • by EmbeddedJanitor (597831) on Monday September 08, 2008 @06:10PM (#24926771)
      Leap days correct our orbit around the sun to keep December/January in the middle of winter for the Northern Hemisphere.

      Leap seconds correct for the rotation of the earth to keep the sun above at noon.

      If we dispense with leap seconds then this relationship will slowly change and noon will eventually be dark.

      • I suppose I'd know that if I'd R'd TFA... :P

        • Keeping leap seconds synced is pretty important across comms networks.
      • Re: (Score:3, Interesting)

        by catmistake (814204)

        Leap days correct our orbit around the sun to keep December/January in the middle of winter for the Northern Hemisphere.

        While true, that is the intent, has any one noticed that this has failed over the last 20 years or so? When I was a child, Winter was Winter, and the first snow fall in the Northeast was usually by Thanksgiving. Over the past couple decades, the first snowfall seems to be pushing itself into late January, mid-February. Used to be, the harshest part of Winter was Dec-Jan, now it seems firmly seated in February. And why is it every year we see an Indian Summer smack in the middle of Winter? By my reckoning, w

        • has any one noticed that this has failed over the last 20 years or so?

          No. Labor Day was as cold in the valley as it usually is in the mountains this year, and trick or treating has consistently required coats for my family for the past 20 years.

          • Well, Labor Day is late Summer, and at elevation weather is always more extreme. Over recent history, haven't you noticed that the snows come later and linger longer? There was a snow storm late March 2 years ago... that just doesn't sit right with me that the biggest storms are arriving post-January rather than early December.

            • Well , my grandma told me, that once, they had snow in mid-June. I guess we need more and more exact data...

        • by Hadlock (143607)

          source? Pretty sure the latest recorded freeze in the DFW area has been april 14th for something like that for more than 30 years. when 80% of the US has only had scientifically accurate weather data for the last 100 year or so. pull up weather records for your area and post them, i'd be interested to see factual evidence support your theory.

      • Yep... (Score:5, Insightful)

        by msauve (701917) on Monday September 08, 2008 @06:42PM (#24927133)
        and if anyone doesn't like leap seconds, all they have to do is use one of the time scales which don't use them, like TAI [wikipedia.org].

        It's exceedingly silly and stupid for people to keep trying to change UTC [wikipedia.org] so it doesn't track solar time. That what it was intended to do. If you made the wrong choice, live with it, or change time scales. If it's being forced on you, quityerbitchin', and convince whoever decided on UTC to change. Stop trying to turn UTC into something it isn't, there are other people out there who made an intelligent decision, and depend on it's characteristics.
        • Re: (Score:3, Insightful)

          by Phil Karn (14620)
          You are absolutely right. UNIX and its derived systems simply made a big mistake in choosing UTC for internal use. They should use an atomic time scale, either TAI or GPS time internally, I don't really care which.

          If they really have to, UNIX could define their own epoch with a zero offset to UTC as of right now. Then timestamps made in the past few years won't have to jump in the changeover. This would give exactly the same benefit as no longer applying leap seconds to UTC without removing UTC's ability

      • by blantonl (784786)

        My God your signature:

        Engineering is the art of compromise.

        And then this quote:

        If we dispense with leap seconds then this relationship will slowly change and noon will eventually be dark.

        Does slowly equal 20 years, or 20,000 years before we're dark? I mean really?!?

      • Re: (Score:2, Funny)

        by nategoose (1004564)
        You had me scared there for a little bit. I thought you were going to explain how dispensing with leap times was going to degrade our orbit and make us either fall into the Sun or fling out into deep space.
      • by Dannkape (1195229) on Monday September 08, 2008 @07:29PM (#24927555)
        According to wikipedia, there seems to have been 24 leap seconds in the last 36 years. For solar noon to move a single hour away would take over 5 millenia.

        Of course, they do give the news something harmless to report on every once in a while...
      • by CorporateSuit (1319461) on Monday September 08, 2008 @07:50PM (#24927739)

        If we dispense with leap seconds then this relationship will slowly change and noon will eventually be dark.

        In that case, we rename "noon" to "midnight", and "midnight" to "noon"
        then "AM" can mean "After-Meridian" and "PM" can mean "Pre-Meridian"
        I thought of everything. Problem solved forever.

        • Re: (Score:3, Funny)

          by Myopic (18616)

          That's a great idea! Actually, let's do one better, and we'll change the names of the times whenever it drifts by six hours: we'll call noon "six o'clock", and whatnot. Actually, gosh, let's go all the way and do it for every hour. So, if we drift by an hour, then we'll rename "one o'clock" "two o'clock", and whatnot. That'll keep it all about right. No, wait, actually, we should do it for every minute -- no, let's do it for seconds! So, every time it gets off by a second, we'll add a second to the middle o

  • Not quite (Score:5, Informative)

    by Deadstick (535032) on Monday September 08, 2008 @06:04PM (#24926709)
    there is a demonstrated way to...keep the sun overhead at noon.

    No there isn't, but you can make it culminate at noon.

    rj

    • Re: (Score:3, Funny)

      Yeah, but anyone close enough to give the sun a nooner would get burned up.
    • No there isn't, but you can make it culminate at noon.

      It depends where you are in your time zone. It's rare for the sun to be directly overhead at noon.

      • Re: (Score:3, Informative)

        by Deadstick (535032)
        It's rare for the sun to be directly overhead anywhere, and impossible outside the Tropics. At noon local standard time (assuming the leap-second problem has been taken care of, per the thread topic), it culminates for an observer on the base meridian of the time zone. It always culminates at noon local solar time -- which is a bit of a tautology, because local solar time is computed from the time when it culminates.

        rj

    • by rrohbeck (944847)

      No there isn't, but you can make it culminate at noon.

      Yes there is: Move to the equator.

      :P

  • by wealthychef (584778) * on Monday September 08, 2008 @06:07PM (#24926731)
    I'd be more interested in killing Daylight Savings Time than dealing with Leap Year.
    • Re: (Score:3, Insightful)

      DST can be "fixed" by recording time in UCT. No such "fix" exists for leap seconds. With leap seconds, you're getting down to the fundamentals of how time is recorded, not how it is translated to local time.

      • by corsec67 (627446)

        Why don't you try to get everyone you interact with to use UTC, then?

        The gp obviously wasn't talking about recording timestamps, which should be in UTC.

      • Re: (Score:3, Interesting)

        by igb (28052)
        Don't be silly. If you need monotonically increasing time, that's what TAI is: constant seconds, no leap seconds, ticked by atomic clocks.. If you need time that works for solar or celestial navigation because you want to sail boats using only a sextant, you use UT0 or UT1, so that the sun is in the right place relative to your watch, but you accept that seconds aren't constant: variations in the movement of the earth appear as variations in the length of seconds. UTC is a convenient compromise, with the
    • Because it doesn't give you enough time during the day to sufficiently explain yourself on /.?

    • by BitterOldGUy (1330491) on Monday September 08, 2008 @06:13PM (#24926839)

      I'd be more interested in killing Daylight Savings Time than dealing with Leap Year.

      My cat wakes me up in the morning. She doesn't adjust. Because of her, I'm a morning person. Unfortunately, 90% of society are night people. Meaning, any social activity is past my bedtime and I become a wet blanket because I start yawning at everything at 20:00.

      • by Anonymous Coward on Monday September 08, 2008 @06:21PM (#24926929)

        I think your REAL problems are as follows:

        You have a cat.

        Your cat controls you.

        You characterize and categorize people (90%, society, night people) in terms of what they can give you (social activity).

        You speak in military (24 hour) time unnecessarily.

        You admit your own faults, but rather than fix them, you prefer to revel in your own meekness.

        • by BitterOldGUy (1330491) on Monday September 08, 2008 @06:54PM (#24927241)

          I think your REAL problems are as follows:

          You have a cat.

          Your cat controls you.

          You characterize and categorize people (90%, society, night people) in terms of what they can give you (social activity).

          You speak in military (24 hour) time unnecessarily.

          You admit your own faults, but rather than fix them, you prefer to revel in your own meekness.

          Dogs have masters.

          Cats have servants.

          I recognize my overlord and serve her. And as a result, my life is filled with a wondrous furry glory!

          The Egyptians worshiped cats as gods and the cats have never forgotten that.

          Military time is also computer server time. And if you deal with computers across at least one time zone you may want to use Zulu time too. Oooooo, I used another military term. You know why!? Because, I serve in the army of cats!

      • by fm6 (162816)

        And in fact people who work with animals are the biggest opponents of DST. Their livestock refuses to change its habits just because clock time has changed.

        What, you say you don't work with animals? Yes you do. You're a cat servant.

    • by Kjella (173770) on Monday September 08, 2008 @06:32PM (#24927035) Homepage

      Killing it? I want to change them completely, and wintertime too. Now, I live a bit further north than most people (60 degrees latitude) and what happens in the winter is that I, like most people, head to work in the dark and come home in the dark. Maybe you get to see some sun on your lunch break, but unless you got an office with a view you won't see much of it otherwise. If we have like 6 hours of sun, they should be 4PM-10PM so you can do some outdoor activity after work. What happens now is I sit indoors during the day because of work, and I sit indoors in the evenings because it's dark and cold outside. I haven't got any stats to back it up but I'd think most people work indoors these days, the reason to have light == noon so you could run around outside just isn't there. I'd be happy with mornings that suck (some more) and evenings that were bright and nice all year round.

      • by corsec67 (627446)

        Why not see if you could get to work at (say) midnight, so that when you get home it is morning?

        How about instead of redefining time, you change what the times mean?

        That is my complaint about DST: instead of leaving it up to businesses to start work at 9 instead of 8, they have to mandate that the whole concept of local time changes.

        • by Kjella (173770)

          Why not see if you could get to work at (say) midnight, so that when you get home it is morning?

          It's not the "getting to work" part, it's the "staying employed" part. Very few jobs, even with flexible hours will accept that you're never around during normal business hours. And the whole bit about social events which would then happen at "nighttime" for you.

          That is my complaint about DST: instead of leaving it up to businesses to start work at 9 instead of 8, they have to mandate that the whole concept of local time changes.

          It's not like they're warping the time stream or anything, it's just digits on a watch and there's no law saying businesses can't "un-DST" their business hours. Can it be that what you really have a problem with is being an hour out of synch with ev

      • But think of the children!

        No, really.

        How the hell am I going to go to sleep and wake up in time?

        3PM-9PM, with the sun completely down at 10PM would be pretty sweet. I mean, I'm in school all day, and they're leaving the lights on anyway, so why not? I finish school and it's bright out, it's so great to go outside! It would encourage us to get off our fat asses too. No more excuses. It's now sunny outside when you don't have work.

    • by zappepcs (820751)

      Yes, indeed. I was hoping to find an explanation in comments... I don't have TIME to read the articles... sigh

  • This adding of leap seconds based on decisions by panels of experts or authoritative bodies is a nonsense.

    If you're going to do this sort of thing - adding seconds to the clock here or there - it shouldn't be decided upon by some review committee. There should be a planned algorithm that kicks in, and the simplest one that actually does the job should be used. The bottom line is that a watch should be able to do it. If you do this, you're able to program devices to account for leap seconds instead of having

    • by klapaucjusz (1167407) on Monday September 08, 2008 @06:27PM (#24926991) Homepage

      There should be a planned algorithm that kicks in,

      This assumes that we know when, in the future, we'll need to insert leap seconds. And we don't.

      Leap seconds are introduced in order to compensate for medium-term variations in the earth's rotation speed. We don't have a good understanding of the way the earth rotates -- knowing what UTC time it will be in ten years' time is about as difficult as predicting the weather for next week-end.

    • The Earth's rotation varies somewhat unpredictably and thus there's no simple way of automatically adding/subtracting leap seconds without observation first.

      Communications, such as cellular phone networks, often depend on very precise syncronized timing.

      Ron

    • Re: (Score:2, Interesting)

      by surmak (1238244)

      If you're going to do this sort of thing - adding seconds to the clock here or there - it shouldn't be decided upon by some review committee. There should be a planned algorithm that kicks in, and the simplest one that actually does the job should be used. The bottom line is that a watch should be able to do it. If you do this, you're able to program devices to account for leap seconds instead of having to manually put in fudges which is an error prone process. You also get the possibility of adding leap milli-seconds or micro-seconds so fine grained adjustments are possible where required, whereas it would be much harder (though not impossible) to do that if you're manually correcting.

      It cannot be done. Leap seconds are dependent on unpredictable, chaotic natural events -- namely the fact that one day in not exactly 24 hours in length. The daily error is not constant, so the only way to determine when a leap second is required is through astronomical observations.

    • by John Hasler (414242) on Monday September 08, 2008 @06:36PM (#24927075) Homepage

      > There should be a planned algorithm that kicks in, and the simplest one that actually
      > does the job should be used.

      There is none. The rate of rotation of the Earth is slightly irregular in a not entirely predictable way.

      > I don't think I even own a time keep device where this level of accuracy matters.
      > Perhaps my GPS?

      Definitely your GPS. It cares about nanoseconds.

  • by jayveekay (735967) on Monday September 08, 2008 @06:18PM (#24926893)

    We don't need even one more second of Bush presidency. :)

  • increasing time?

    Yeah, I guess the clocks would have to take into account the increases in orbits and whatnot mentioned, but so what? Computation has become dirt cheap. So the Naval Observatory does an extra calculation for GPS and things that require that kind of accuracy.

    And as far as I'm concerned, my clocks are all within 10 minutes of each other - in other words, I don't give a shit about 10 minutes either way.

    • I don't give a shit about 10 minutes either way.

      It depends on the application. Having one's NFS file server just a second fast will break most Makefiles.

      • Re: (Score:3, Funny)

        by robo_mojo (997193)

        It depends on the application. Having one's NFS file server just a second fast will break most Makefiles.

        I think that says more about make than it says about timekeeping.

      • Nah. It just gets bitchy. "Blah blah has modification time in the future!"

        You might wind up generating a couple of .o files more than you need to, but I wouldn't call that breakage.

        Now, an NFS server that's running SLOW, OTOH....

    • by rrohbeck (944847) on Monday September 08, 2008 @07:23PM (#24927509)

      That's exactly the point. Changing software in military or even space systems isn't exactly trivial, maybe not even possible, plus you need a method to constantly provide (UT1-UTC) to the systems that rely on UT1 (astronomical time) being equal to UTC by less than a second. Like the radio controlled clock in your home. Or the time signal transmitters would have to be redefined not to transmit UTC but some new time scale, which would be a mess for GPS.

      UTC without leap seconds is basically TAI (international atomic time) - a strictly linear SI second timescale as precise as we can reproduce it.
      Just distribute (TAI-UTC) and (UT1-UTC) together with the usual time signals, leave UTC alone (with leap seconds) and you're all set and can use what you need. There is no one time scale; Einstein told us so. Better accept it.

      • Just distribute TAI, publish zoneinfo with leap seconds included, and calculate whatever you need for local use or display as needed.

        • by compro01 (777531) on Monday September 08, 2008 @08:55PM (#24928225)

          The problem being, the need for a leap second is not predefinable, unlike a leap day. Leap seconds are needed to compensate for slight (millisecond range) variations in the length of each day, due to the earth's rotation speed not being constant. We currently cannot predict those variations, and as such, the leap seconds are determined based on astronomical observation and applied as needed.

          • Re: (Score:3, Insightful)

            by John Hasler (414242)

            > We currently cannot predict those variations, and as such, the leap seconds are
            > determined based on astronomical observation and applied as needed.

            I know that, but zoneinfo has to be updated frequently anyway to accomodate the whims of princes.

  • I know! (Score:5, Funny)

    by tnk1 (899206) on Monday September 08, 2008 @06:52PM (#24927225)

    Let's just remove the problem entirely!

    I suggest... the French Republican calendar.

    And a good Tridi, 23 Fructidor, Year 216 to you too.

  • Why don't we just get Superman to fly around the Earth really fast to slightly change its rotation. If he can reverse time, surely he could adjust it sightly so that everything would work out.
  • by k1e0x (1040314) on Monday September 08, 2008 @06:58PM (#24927283) Homepage

    I don't understand what the DoD has to do with time, standards or measurements.

    Is the DoD trying to say now Muhahaha! Now we control time itself, submit all ye to "civilian time"?

    We need to get the opinion of an expert, not some random poll.. perhaps the DoD should seek the advice of the master of timecube theory Dr. Gene Ray.

  • Who gives a damn about the sun being overhead at 12PM? China operates in a single timezone, despite spanning something like five, and they do just fine.

    Give us GMT. Let noon drift where noon drifts. Just keep the seasons in line with the longest and shortest days and forget the rest.

  • The problem isn't with UTC or TAI or any other timekeeping system used by the world.

    The problem is with the cheap crap you have in your home which assumes every day is 86400 seconds long and every year is 365 days.

    You bought it, you adjust it. I got better problems to solve.

  • by PPH (736903) on Monday September 08, 2008 @09:21PM (#24928403)
    What significance does this have for people who live in their parents' basement?

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