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Topic: Leap-second

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In the News (Mon 20 Nov 17)

 Leap second - Wikipedia, the free encyclopedia
Leap seconds are used to keep time standards synchronized with civil calendars, the basis of which is astronomical.
Leap seconds occur only at the end of a UTC month, and have only ever been inserted at the end of June 30 or December 31.
Leap seconds are necessary because time is measured utilizing stable atomic clocks (TAI or International Atomic Time), whereas the rotation of the Earth has been slowing down.
en.wikipedia.org /wiki/Leap_second   (1950 words)

 The NTP Timescale and Leap Seconds
Leap seconds were inserted prior to 1 January 2006 on the occasions listed in the leapseconds file, a current copy of which can be obtained from NIST or via the NTP Autokey security protocol.
The intervals between leap insertions has been increasing; the interval since the next scheduled leap second at the end of 2005 and the last one at the end of 1998 was seven years.
Thus, all previous leap seconds, not to mention the apparent origin of the timescale itself, lurch backward one second as each new timescale is established.
www.eecis.udel.edu /~mills/leap.html   (1423 words)

 NIST Time and Frequency FAQ
Leap seconds are needed so that users of the astronomical time scale (UT1) can use UTC and know that the difference between the two time scales is never greater than 0.9 seconds.
When a leap second is necessary, an announcement is made at least several months in advance, and all leap seconds so far have been implemented on either June 30th or December 31st.
The first leap second was added on June 30, 1972.
tf.nist.gov /timefreq/general/leaps.htm   (497 words)

 NIST Time Scale Data Archive
Leap seconds are used to keep the difference between UT1 and UTC to within ±0.9 s.
All leap seconds listed in the table are positive leap seconds, which means an extra second is inserted into the UTC time scale.
The first leap second was inserted into the UTC time scale on June 30, 1972.
tf.nist.gov /pubs/bulletin/leapsecond.htm   (354 words)

 Leap seconds
Leap seconds are inserted at the end of June or December as an additional second after 23:59:59 UTC (Universal Time Coordinated).
It is also possible to have a negative leap second, where one second is removed, in a case where the Earth is rotating faster, but such a negative second has never been used, and is rather unlikely to be used in the future.
The difference between UTC and TAI was defined as 10 seconds from January 1972 and the first leap second was added in June 1972.
www.timeanddate.com /time/leapseconds.html   (842 words)

 BBC NEWS Science/Nature New Year 'delayed' by leap second
The new leap second will be inserted at the end of the final minute of 2005, giving the familiar "six pip" BBC radio time signal an extra pip before the long pip marking the hour.
Leap seconds are required every so often to keep our clocks in sync with solar time used by astronomers.
A leap second is added to Co-ordinated Universal Time (UTC) to keep it in step with solar time- based on the Earth's rotation on itself - to within a second.
news.bbc.co.uk /1/hi/sci/tech/4562194.stm   (286 words)

 Leap seconds
Leap seconds were introduced in 1971 to reconcile astronomical time, which is based on the rotation on the Earth, and physical time, which can be measured with amazing accuracy using atomic clocks.
Leap seconds have to be inserted on average every 1–2 years during this century.
Abandoning leap seconds in the international standard time would not cause any problems for computer systems that are not involved in controlling astronomical or aerospace systems, as long as national/regional civilian time zones do the same.
www.cl.cam.ac.uk /~mgk25/time/leap   (2123 words)

 Future of Leap Seconds
Given that UTC with leap seconds originated in 1972, and that atomic time did not exist before 1955, it is not clear that any meaning dare be attributed to the fractional bits of the NTP clock during most of the first half of the present NTP era.
Note that the effective date of the end of leap seconds proposed by the 2004 contribution of the United States is 2007-12-21 which is less than two months after the conference.
Finally, as a result of the invention of leap seconds, systems designers and the general public have not had to recognize that time-of-day (universal time) and time interval (atomic time) are two distinct and incommensurate quantities.
www.ucolick.org /~sla/leapsecs/onlinebib.html   (12489 words)

 CNN.com - Earth orbit slows no more, baffling scientists - Jan. 2, 2004
The leap second was an unexpected consequence of the 1955 invention of the atomic clock, which use the electromagnetic radiation emanated by Cesium atoms to measure time.
Leap seconds can be a big deal, affecting everything from communication, navigation and air traffic control systems to the computers that link global financial markets.
To make the world's official time agree with where the Earth actually is in space, scientists in 1972 started adding an extra "leap second" on the last day of the year.
www.cnn.com /2004/TECH/science/01/01/leap.second.ap   (285 words)

 NIST Tech Beat - Dec. 21, 2005
A recent proposal to eliminate leap seconds altogether in the future is still under consideration by the international bodies in charge of coordinating world time.
This year's leap second will be implemented by adding an extra second to atomic clocks at NIST in Boulder, Colo., and other sites around the world.
Since 1999 until recently, that rotation and UTC had stayed closely enough in harmony to not require the adjustment of adding a leap second.
www.nist.gov /public_affairs/techbeat/tb2005_1222.htm   (1986 words)

 LiveScience.com - Extra Second Will be Added to 2005
The once-common "leap second" is the first in seven years and reflects the unpredictable nature of the planet's behavior.
The first leap second was added in 1972, as technology allowed for more accurate timekeeping, and they were all the rage in the beginning.
An extra second will be added to 2005 to make up for the slowing down of the Earth's rotation.
www.livescience.com /technology/050705_leap_second.html   (627 words)

 Geek.com Geek News - One leap second to be added to 2005
The leap second will be added just before 00:00 UTC between 2005 and 2006, so if you don't live in that timezone it will affect you at some other time during the day, for example just before 7 PM (12/31) in New York (Source).
The first leap second was added on June 30, 1972, and the last one was added in 1999.
One arc second of orbit of the planets Jupiter or Pluto is a very large distance travelled and a crucial measure to be made when sending expensive space craft to snoop around the surfaces of those planets.
www.geek.com /news/geeknews/2005Dec/gee20051226033965.htm   (2016 words)

 New Year’s Day 2006 delayed by a second - U.S. Life - MSNBC.com
Scientists are delaying the start of 2006 by the first “leap second” in seven years, a timing tweak meant to make up for changes in the Earth’s rotation.
Although it is possible to have a negative leap second --that is, a second deducted from Coordinated Universal Time --so far all have been add-ons, reflecting the Earth’s general slowing trend due to tidal braking.
The first leap second was added on June 30, 1972, according to NIST, an arm of the U.S. Commerce Department.
www.msnbc.msn.com /id/10605881   (392 words)

 Why the US wants to end link between time and sun
But adding these ad hoc "leap seconds" -- the last one was tacked on in 1998-- can be a big hassle for computers operating with software programs that never allowed for a 61-second minute, leading to glitches when the extra second passes.
Eliminating leap seconds will make sextants and sundials slowly become inaccurate, but supporters say that's OK now that the satellite-supported GPS can give exact longitude and latitude bearings to anyone with a receiver.
The U.S. effort to abolish leap seconds is also firmly opposed by Britain, which would further lose status as the center of time.
www.post-gazette.com /pg/05210/545823.stm   (1220 words)

 U.S. Naval Observatory to Add Leap Second to Clocks SpaceRef - Your Space Reference
Leap seconds are added because the Earth's rotation tends to slow down relative to atomic time.
This leap second is occuring seven years since the last one.
This marks the 23rd leap second to be added to UTC, a uniform time-scale kept by atomic clocks around the world.
www.spaceref.com /news/viewpr.html?pid=18607   (929 words)

 jwz - Happy Leap Second
However, the leap second was corrected by NTP during the daily run.
p-second.htm seems to confirm that: "If an NTP daemon detects a leap second announcement, it passes the announcement on to its clients, and notifies its own operating system clock of the upcoming leap second, if the operating system is aware of leap seconds.".
This decision is widely complained about to this day, but its also somewhat understandable — it'd be somewhat gross to require libc have access to an up-to-date list of leap seconds just to handle localtime() Therefore the kernel's idea of time_t must be set after each leap second event.
jwz.livejournal.com /585295.html   (798 words)

 BBC NEWS Science/Nature Leap second talks are postponed
The first leap second in seven years will be added at the end of 2005.
Leap seconds synchronise clock time with solar time used by astronomers.
Daniel Gambis, of the Earth Rotation Service in Paris, which decides when to add or subtract leap seconds, told the BBC: "For me, it would be a problem if the Sun were to rise at 4pm or at a different time like noon or midnight.
news.bbc.co.uk /1/hi/sci/tech/4420084.stm   (543 words)

 Scotsman.com News - Sci-Tech - Happy New Year . . one second late
Leap seconds were introduced in 1972, but this is the first to be applied for seven years.
To compensate for the effect, a "leap second" is to be added to the end of today, meaning the traditional Hogmanay countdown tonight will now end at 00.00.01.
Clocks are based on Greenwich Mean Time, which is tied to Sun's position in relation to the Greenwich Meridian - the zero line of longitude.
news.scotsman.com /scitech.cfm?id=2480912005   (397 words)

 2006 Will Be Delayed By A Second - CBS News
Leap seconds are needed occasionally because modern atomic clocks measure time with great accuracy, while the rotation of the Earth can be inconsistent.
A leap second will be inserted in the world's clocks just before midnight, Greenwich mean time, on New Year's Eve, the U.S. Naval Observatory reported Friday.
This will be the 23rd leap second that has been inserted since 1972 when an international timekeeping agreement was signed, according to the Observatory.
www.cbsnews.com /stories/2005/12/23/tech/main1164025.shtml?cmp=EM8707   (287 words)

 Leap Seconds
Over the course of one year, the difference accumulates to almost one second, which is compensated by the insertion of a leap second into the scale of UTC with a current regularity of a little less than once per year.
Since the first leap second in 1972, all leap seconds have been positive and there were 23 leap seconds in the 34 years to January, 2006.
The confusion arises because some mistake leap seconds for a measure of the rate at which the Earth is slowing.
tycho.usno.navy.mil /leapsec.html   (1741 words)

 Take an extra second this year to reflect on 2005
In a 24/7 world, leap seconds that adjust the timekeeping of atomic clocks to the time based on the rising and setting of the sun are viewed by many technocrats as a nuisance.
Yep, it's a leap second moment, one of those rare occasions when clocks around the world take a stutter step in order to conform with the Earth's wobbly, gradually slowing spin.
If 2005 is disappearing too fast for you, just hold on for a second, because this year you have an extra second to pause and reflect on the year before the ball drops and the calendar flips New Year's Eve.
seattlepi.nwsource.com /national/253531_leapsecond27.html   (463 words)

 2006 Postponed by One (Leap) Second
As the Earth slows, the addition of leap seconds will be required more frequently to keep the Earth and atomic clocks in sync.
To keep today's atomic clocks synchronized with time as measured by Earth's rotation, timekeepers insert a leap second whenever the difference between the two clocks exceeds nine-tenths of a second.
The extra second will allow Earth to stay in sync with the ultraprecise clocks, which mark time based on the vibration of atoms.
news.nationalgeographic.com /news/2005/12/1229_051229_leap_second.html   (558 words)

 'Leap second' to be added on Dec. 31 News.blog CNET News.com
The first leap second was added in 1972, and often the extra second has been added at the end of June instead of the end of December.
The adjustment, called a leap second, takes place whenever Coordinated Universal Time is out of synch with the planet's time by more than 0.9 seconds.
The last time a leap second was added was 1998, but usually they're added slightly less than once each year, NIST said.
news.com.com /2061-11204_3-6009898.html   (331 words)

 The Why Files Leapin' leap second
Throwing the leap second to the sharks, they say, will make it easier to develop and maintain global positioning satellites (GPS) and computer communications.
They say people who operate GPS and other time-critical gadgets have trouble accounting for leap seconds, which are somewhat unpredictable and thus tough to factor into software.
But in 1972, after the invention of the hyper-accurate atomic clock, timekeepers began slipping in a leap second every few years, so atomic-clock time would jibe with time derived from Earth's position in space.
whyfiles.org /shorties/187timeout   (968 words)

 USATODAY.com - A one-second argument
However, leap seconds are added whenever necessary to keep it in step with solar time to within 0.9 seconds.
The Royal Astronomical Society accuses those eager to drop leap seconds of trying to solve the problem of precision timing by "exporting problems" to those who use clock time as a measure for solar time.
One second is the duration of 9,192,631,770 cycles of the frequency of radiation from cesium atoms.
www.usatoday.com /tech/science/2005-10-12-leap-second_x.htm   (600 words)

 Random Developments - Leap second
This is caused by the rotation of Earth slowing down, and is not that uncommon; the last time we had a leap second was in 1998.
Someone in a mailing list mentioned that 2005 will have a leap second on 31 December, just before the year ends (ABC has a nice report about this).
This means that the minute starting at 23:59:00 on that day will have 61 seconds (23:59:57, 23:59:58, 23:59:59, 23:59:60, 00:00:00).
www.netwhatever.com /weblog/random/archives/000610.html   (171 words)

 NIST Tech Beat - December 19, 2003
The second step involves testing exposed cells for a specific protein in the cell membrane, the presence of which indicates cells are dying.
From 1972 (when the world went to the current system of atomic timekeeping) until 1999, 22 seconds were added to the world’s time in order to keep atomic time synchronized with Earth& time, as measured by the Earth& spin.
Within 40 seconds “flashover” occurs— that’s when flames completely engulf the room, depleting the oxygen and turning the atmosphere into toxic smoke and other searing gases.
www.nist.gov /public_affairs/techbeat/tb2003_1219.htm   (1512 words)

By resetting the clock at each leap second, xntpd extracts a correct UTC display (except, of course, during leap seconds) from the broken localtime() libraries.
Before the leap second, the TAI-UTC difference was 30 seconds; after the leap second, the TAI-UTC difference was 31 seconds.
By inserting occasional leap seconds into UTC, astronomers slow down UTC's progression to match Earth's rotation.
cr.yp.to /proto/utctai.html   (623 words)

 Ways to Use Your 2005 Leap Second
The world's extremely accurate atomic clocks will be adjusted by one second this year to compensate for the miniscule slowing down of Earth's orbit.
Multiply that by one second, and collectively we have an extra 204 years on our hands.
Now that there's nothing on but crappy reality programming, one second is about all you can take anyway.
www.thespeciousreport.com /2005/05050707leapsecond.html   (246 words)

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