Leap Second At The End of 2005

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 ;)

Comments

How did you use yours?

[Chemisor]

And, of course, I already used it to read Slashdot. Oh, darn...

Re:How did you use yours?

[Extrudedaluminiu]

Do any NTP servers keep track of these seconds?

Re:How did you use yours?

[tonsofpcs]

Most NTP servers use UTC time, so yes.

http://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat - leap second bulletin

Re:How did you use yours?

[lousyd]

Do any NTP servers keep track of these seconds?

Yes, that's the point of serving the Network Time Protocol...

Re:How did you use yours?

[Yocto Yotta]

What does it matter now! I gotta reset ALL of my clocks again. Damn it.

Re:How did you use yours?

[Anonymous Coward]

There's a rumor going around that ~25000 Linux boxes running a custom 2.4.22 kernel crashed over at Yahoo! because of the leap second change.

Re:How did you use yours?

[fm6]

Everybody uses UTC. For official purposes, every non-solar clock is UTC, at varying degrees of accuracy, modified by the local time zone.

(By "solar" I don't just mean sundials. I mean clocks that are set by pointing the hour hand straight up at noon, which is how all clocks were set before time zones were invented.)

I think what you were trying to say is, "most NTP servers are corrected against official UTC time signals."

Re:How did you use yours?

[rossdee]

"(By "solar" I don't just mean sundials. I mean clocks that are set by pointing the hour hand straight up at noon, which is how all clocks were set before time zones were invented.)"

How do they know its noon then?

(Its overcast here)

Re:How did you use yours?

[Trogre]

Silly.

They used 747s to fly the clocks above the clouds.

A cool thing to do

[rolypolyman]

If you watch carefully for that leap second, you can do a freeze-frame flying kick like in The Matrix.

Re:A cool thing to do

[rubycodez]

I didn't see anything as cool as that during the leap second, but a cat did walk by twice.

The hard way

[Anonymous Coward]

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?

Re:The hard way

[MyLongNickName]

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.

Re:The hard way

[jacksonj04]

My clock is set by radio and has no manual adjust, you insensitive clod!

Re:The hard way

[MyLongNickName]

Only problem is that I spend most of my time indoors,

This is Slashdot. Quit spamming us with stuff we already know.

Re:The hard way

[Fishstick]

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.

Re:The hard way

[dotgain]

The trick for someone like you is to find someone else who does go outside, and let them take your watch for a little while. How long between signals until your watch wears runs far out of sync?

Re:The hard way

[jc42]

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.

For mountains, you don't want to just level them; you want to move the mass closer to the axis. So you want to pile the rubble on the poleward side of where the mountain used to be (north in the northern hemisphere, etc.).

Re:The hard way

[Kjella]

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.

If you have ten second-exact clocks in your house, someone has a very serious issue. If you believe 99,999,999 other households have ten second-exact clocks in their home, someone definately has a very serious issue. Besides the geeky solution is to have all of them synchronized automagically, what are you doing on slashdot?

Re:The hard way

[supersat]

You might be joking, but the US actually does want to abolish leap seconds. As a compromise to keep UTC somewhat in sync with UT1 (time as measured by astronomical observations), a leap hour would be inserted every 500-700 years.

I wish I were making this up.

countdown

[Anonymous Coward]

10,9,8,7,6,5,4,3,2,1,0,-1

-Sj53

Re:countdown

[thatnerdguy]

that's one second too many

Damn!

[Black Parrot]

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.

Highlights problem with ntp...

[Dr. Zowie]

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.

Re:Highlights problem with ntp...

[thehickcoder]

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.

Re:Highlights problem with ntp...

[DrPepper]

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 kind of precision, then you use a direct time source such as a GPS signal - a common secondary use of the atomic clocks onboard the satellites. The only way to get better precision than that is to get your own atomic clock :-)

Re:Highlights problem with ntp...

[Dr. Zowie]

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.

Re:Highlights problem with ntp...

[Floody]

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.

Re:Highlights problem with ntp...

[Jaseoldboss]

According to the FAQ on the NTP homepage "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 service and they are the same. So it seems that NTP must have observed leap seconds contrary to your original post.

Re:Highlights problem with ntp...

[OOGG_THE_CAVEMAN]

No widely-recognized data show *any* evidence for variance in the speed of light. Physicists are so certain of this that they have actually *defined* the speed of light as a basis for standards of measurements.

Furthermore, any such idea *still* has nothing to do with leap seconds. That you refuse to acknowledge your mistake shows you are extremely confused about the issue.

Re:happy new year

[SpinJaunt]

More along the lines of 730 days if you include the dupes..

time.gov

[srblackbird]

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

Re:time.gov

[Rytsarsky]

Screenshot: http://flickr.com/photos/jk3us/79978824/

Re:Happy New Year

[Shimmer]

"Happy New Year's" is short for "Happy New Year's Day".

How did you spend the extra second?

[House of Usher]

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

[Viriatus]

Old news, from last year.

It's not the 'ephemeris second' that's the problem

[Jonathan McDowell]

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.

Great

[the eric conspiracy]

Gotta love those long weekends!

Re:Happy New Year

[xenotrout]

REALTOR® is actually a registered trademark, which seems much like "realator" as you say. Although it does sound like it could be an "official" contraction, it's made up.
If you care to know, someone decided, it would seem, to make up a word in order to create "de facto regulation" of an industry--that is, anyone can call themselves real estate agents, but only those who get trademark license (possibly by passing a test on how well they understand real estate agency or REALTY) can legally call themselves REALTORs. And people are "supposed" to prefer a REALTOR over a real estate agent (at least that's the hope of the company owning the name REALTOR--I don't know whether it works or not).

Re:BBC TV yesterday

[Anonymous Coward]

On BBC 1, the clock was counting down and went 5-4-3-2-1-1-0. The people in the streets were just waiting for the bell of Big Ben to strike midnight -- there's no second hand.

The clock problems

[Antony-Kyre]

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?

Re:The clock problems

[DAldredge]

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.

Re:The clock problems

[Hillman]

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.

Re:The clock problems

[PPGMD]

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.

Re:The clock problems

[isorox]

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. Other regions outside London recieve their feeds via various routes.

DTT is sent seperatly, and the signal is encoded (with major delay) as a low bitrate (to the local transmitter), and a high bitrate (to nations/regions) which can be opted out of (I'm a little hazy on this bit).

Additonally DSat is encoded then uplinked to a satelite.

As a consumer, if you recieve digital there will be an additional delay in decoding.

The point is that the time might be fine in the studio, however it goes through a lot of equipment that adds a lot of delay, and different networks will have different delays, different equipment etc.

Now how do you line your studio up? Based on the studio output, the analog reception from a nearby transmitter, the analog reception from a 2nd or 3rd level slave, the digital reception from one of many different transmitters (each with different equipment encoding with a different delay), from satelite (with the 3/4 second bounce plus digital encoding), and how do you account for various decoders?

That's the problem for a normal new year broadcast. Add in a leap second (99% of equipment out there will not accept 23:59:60 as a valid time) and you've got even more problems.

In the UK the most accurate broadcast signal you'll get is the pips on Radio 4 LW.

If you want to know the real time, get a GPS system.

Re:And those with computers...

[anothy]

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.

Leap Second Lovers Are Traitors Says Bill O'Reilly

[Fishstick]

"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

tsunami caused rotation change

[zontroll]

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
(scroll down to the sixth question)

Re:It's not the 'ephemeris second' that's the prob

[Jonathan McDowell]

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 civil time. There's a problem that many technical applications - for instance a lot of stuff at NASA - use UTC in places where it would really make more sense to use TT or TAI, causing needless software grief.

Log of Atomic GPS Clock adjustment

[BiggRanger]

I did up a project on sourceforge.net a few years back to sync my computers with a GPS http://atomicgpsclock.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

Re:Missed it?

[imthesponge]

It's inserted at UTC 23:59:59, which would be 6:59:59 PM in New York.

Re:GPS not synchronized?

[tugrul]

The relationship between GPS and UTC is broadcast from the constellation in the navigation data stream that also transmits time stamps, satellite ephemerises, a variety of correction parameters and other stuff I don't understand/remember :)

Re:GPS not synchronized?

[MDMurphy]

GPS time just counts intervals, and it started the count in weeks, days, seconds in January, 1980. The system is aware if UTC though, and one of the various messages sent from the satellites includes the UTC offset. So if you receive and decode that message you'd know the UTC time.

As of yesterday, the difference between UTC and GPS time is 14 seconds.
http://maia.usno.navy.mil/ser7/series14.txt

last year the US proposed to cancel this update

[Herve5]

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

WWV

[spaceyhackerlady]

>blockquote> 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

I listened to it on WWV. They drop the 29th and 59th tick of each minute, and at 2359 UTC it sounded like (I counted the seconds myself):

tick (57)
tick (58)
silent (59, as usual)
silent (60, leap second)
BEEP (0000 UTC 1 January 2006)
titick
titick
titick
tick
tick

...and so on. The UT1 time correction went from -0.6 to +0.3 seconds. It's encoded in the double ticks.

Yes, I got a recording. Lame or what?

...laura

Re:Why bother?

[NixieBunny]

The folks who are into time are now realizing that the leap second was a sorta bad idea, since it is inserted with little advance notice and is not deterministic.The leap hour idea is being considered and would indeed solve the problem.

The big argument about leap seconds is that the computer folks want to eliminate them, but the astronomers are upset because the useful bit of information that tells how many seconds TAI is off from UTC is transmitted in a field that can only hold a number up to +/- one second in some time transmission protocols. So after a missed leap second, asatronomical time wil lbe off from UTC by an unspecified amount, which could be bad for anyone who uses UTC time to do astronomy. (Since UTC is the time that's transmitted around the world, this is important.)

Re:Typo

[eobanb]

Double "the" in article:

In order to ensure that the the atomic time ...

No, that's a leap the.