Talk:Leap second

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Time (Rated C-class, Low-importance)
WikiProject icon This article is within the scope of WikiProject Time, a collaborative effort to improve the coverage of Time on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 Low  This article has been rated as Low-importance on the project's importance scale.
 


I removed the "Citations needed" tag[edit]

I removed the citations needed tag, since the article seems to have plenty of citations, and no {{cn}}" annotations. If anybody has a specific fact they would like cited, then please do say. Thue (talk) 13:17, 29 June 2012 (UTC)

What about 60 cycle 120 vac power that runs wall clocks?[edit]

What about 60 cycle 120 vac power? That runs wall clocks and is kept very accurate so they do not drift. Do they adjust the cycles on the last 24 hours or what? Wall clocks can not change quickly like a digitalbut there must be a way to adjust. Garylcamp (talk) 22:03, 29 June 2012 (UTC)

See Utility frequency#Stability. — Joe Kress (talk) 22:18, 29 June 2012 (UTC)

Screenshot[edit]

I like the screenshot (got one myself). I like that it's actually a UTC time, compared to the previous Central Time image (and my new Pacific Time image). However, it's odd that it reads "Right now, the official U.S. time is". I know why it does, but perhaps crop that image to exclude that line. (On the other hand, the source is from NIST in the U.S., so I suppose it could be considered the "official U.S. UTC time".) goodeye (talk) 01:28, 1 July 2012 (UTC)

Negative leap seconds[edit]

The article should mention that leap seconds can be either added or removed. The article currently gives the impression that they can only be added. Thue (talk) 19:34, 4 July 2012 (UTC)

The article states "A negative leap second would suppress second 23:59:59 of the last day of a chosen month, so that second 23:59:58 of that date would be followed immediately by second 00:00:00 of the following date. However, since the UTC standard was established, negative leap seconds have never been needed." Jc3s5h (talk) 20:26, 4 July 2012 (UTC)
It would probably help to insert explicit references to ITU-R TF.460 both here and on the UTC page. The ITU-R made the recent versions of this defining document openly available starting in December 2010.Steven L Allen (talk) 02:00, 12 July 2012 (UTC)
Although recent versions are useful for current practice, they are useless as historical documents. Only the 1970 and 1974 versions of CCIR Recommendation 460, or a reprint of them, or of their leap second sections would serve that purpose. — Joe Kress (talk) 08:36, 12 July 2012 (UTC)
US NBS reprinted the 1970 original Rec. 460 on page 31 of Monograph 140, Time and frequency: theory and fundamentals (Byron E. Blair, 1974). Prior to that it also reprints numerous other original defining documents about the SI second and TAI.Steven L Allen (talk) 18:31, 12 July 2012 (UTC)

Why can't the abolition movement just change to using TAI?[edit]

I am curious why the article makes no mention of the idea that those who wish to abolish the leap second might do better simply to use the existing TAI time system for their purposes rather than altering UTC to make it resemble TAI. We've had TAI since the 1950s, and it does what those who seek to abolish the leap second want a timescale to do. Why don't they just switch from using UTC to using TAI? If there are any interesting reasons why they would rather alter UTC than switch to using the existing TAI system, those reasons ought to be discussed in this article.

I'd edit the article to discuss these reasons myself, if I knew of any. But if there are no good reasons, that point ought to be addressed in the article as well, and I'm not enough of an expert in this subject to make assertions about the absence of good reasons.

In particular it's kind of crazy that we already have GPS time, which is a variant of TAI that differs from it by a constant offset. Abolishing the leap second would just leave us with a third such constant-offset-differing timescale when TAI is already adequate for all such purposes. Reasons for wanting to multiply the number of constant-offset atomic timescales should be discussed in this article, if such reasons exist.

--arkuat (talk) 23:41, 26 July 2012 (UTC)

Only arguments that have been reported in reliable noteworthy sources should go in the article. But I suspect the reason many of these sources have not adopted TAI is that it is not the legal civil time anywhere in the world. Many systems must keep legal time, and many other systems must interface with systems that are keeping legal time. Jc3s5h (talk) 03:08, 27 July 2012 (UTC)
What is "legal time"? -- Q Chris (talk) 07:23, 27 July 2012 (UTC)


In any country, civil time (rather than "legal time") is the timescale approved for official and commercial use.

In Switzerland for example civil time is defined as UTC+1 (+2 in the summer). So that's what you are required to use, by law, whether in a contract, a bus schedule, a police report or whatever. In the same way that you are required to sell, say, gasoline by the liter.

In practice the civil time of most (all?) countries is based on UTC. So for any system that interact with the outside world using anything else than UTC is not an option. Thus if you are not happy with UTC you can't just use something else, you need the whole word to switch.

TAI couldn't be used directly as we don't want clocks to suddenly jump backwards. Continuity with the current time has to be maintained. Whether you formally introduce a new timescale or change the definition of UTC is a detail.

So the real question, which IMO is not really addressed in the article at this time, is why would you want to abolish leap seconds ?

The main reason is that leap seconds are a huge pain in the butt for computers and networks

Bomazi (talk) 16:39, 17 January 2013 (UTC)

I think the pain in the butt is covered in the first paragraph of the Proposal to abolish leap seconds section. -—Kvng 15:07, 20 January 2013 (UTC)

Ok, I didn't read that part. Bomazi (talk) 21:56, 20 January 2013 (UTC)

One area where "traceable" time comes into play is in the financial markets where messages between traders and stock exchanges are time-stamped and people calculate transmission times between parties to the nearest millisecond and get excited once these take longer than 0.1 seconds. The only way that the times can be measured is for the transmitter to place a timestamp on their electgronic message and for the recipient to note the timestamp upon receipt. Martinvl (talk) 07:47, 21 January 2013 (UTC)

Moving reference longitude[edit]

The traditional (GMT) scheme was to establish mean solar time at the reference longitude of Greenwich, then to relate local civil times to GMT by offsets of (preferably) integer numbers of hours. This translated the mean solar time at the Greenwich reference longitude to a local reference longitude that was a multiple of 15 degrees. Eliminating the leap second is equivalent to abandoning Greenwich's longitude as the overall reference. Neglecting one leap second effectively moves all reference longitudes eastward a quarter of a nautical mile at the equator, an average rate of less than a meter per day at the rate leap seconds have been issued.

Since the vast majority of locations within one time zone are observing a civil time that differs from the true local mean solar time by much more than a second anyway, having the reference moving at so slow a rate can hardly be noticed. In any case, the drawing of time-zone boundaries has so much to do with geography and political borders, and recurs so frequently that so slowly creeping a reference is easily accommodated by tweaking a boundary every century or two.

This concept of a moving reference would seem to satisfy the requirement mentioned for some countries, that civil time be tied to solar time. It places the responsibility on the country's government of drawing and redrawing time-zone boundaries to keep times everywhere within the country reasonably close to the mean solar time at the local reference longitudes, a responsibility they already accept.

I am posting this idea here in the hope that someone will have seen it somewhere else, making it not original research and therefore able to be included in the article. — Preceding unsigned comment added by 70.116.95.245 (talk) 22:52, 9 June 2013 (UTC)

Incorrect edit[edit]

The following was added today:

Applications for which leap seconds cause problems can use one of the other existing time standards, such as TAI, which is the basis for UTC,[1] or GPS time, which may be calculated from satellite-broadcast signals.[2]

[Citations changed slightly to work in talk page.]

References

1. E. Felicitas Arias, Gianna Panfilo, and Gérard Petit (2011-09-11). "Status of UTC/TAI" (PDF). Retrieved 2013-08-20. 

2. Geoffrey Blewitt (1997). "Basics of the GPS Technique: Observation Equations" (PDF). Retrieved 2013-08-20. 

This is not correct. In the earlier part of the edit, it is claimed that TAI is the basis for UTC, which is partly true, but TAI is not broadcast or disseminated, so an application occurring outside a time laboratory does not have direct access to it. Furthermore, TAI is more than 30 seconds different from UTC, which is the defacto basis for civil time throughout the world. So for many applications TAI may not be used instead of UTC.

Which part of "TAI is the basis for UTC" is partly true. If you actually want to argue this further, it is probably best to do so at International Atomic Time or Coordinated Universal Time. ~KvnG 03:15, 25 August 2013 (UTC)

In the later part of the edit it is claimed that GPS time may be calculated from satellite-broadcast signals. This is backwards; GPS satellites broadcast GPS time. They also broadcast data that can be used to calculate UTC from GPS, but some applications cannot obtain the UTC calculation data in time to make use of it.

GPS time is based on TAI. A simple and completely accurate calculation (TAI – GPS = 19 seconds) converts between the two. No calculation data necessary. See Gps#Timekeeping. ~KvnG 03:15, 25 August 2013 (UTC)

Also, the second citation is unacceptable in that it fails to state what page in a 46 page paper supports the claim. Furthermore the strings "UTC" and "coordinated" (with no sensitivity to capitalization) cannot be found in the paper. Jc3s5h (talk) 16:34, 20 August 2013 (UTC)

I agree with this. ~KvnG 03:15, 25 August 2013 (UTC)

Dubious edit[edit]

user:Rightismight made this edit, with no citation provided. Rightismight asserts

In the event the ITU resolution passes and leap seconds are no longer inserted, special Network Time Protocol and other time servers could be set up that provide UT1 rather than UTC. Those astronomical observatories and other users that require UT1 could run off that time - although in many cases these users already downloaded UT1-UTC from the IERS, and apply corrections in software.

However, one of the concerns frequently raised is that no though analysis has been done to determine which systems will fail if leap seconds are eliminated. Not knowing which systems will be affected, there is no way to assess how effective a particular solution would be. Also, it is not known whether the systems will be accessible to make any software updates that may be required, or whether the documentation and skills that would be needed to update potentially old systems still exist.

Such a statement ought not to be made by a Wikipedia editor; it must come from a reliable source. Jc3s5h (talk) 02:23, 4 July 2014 (UTC)

I have added a reference, from a respected scientist, made at a well-known conference on this matter. Hope this is considered sufficient. — Preceding unsigned comment added by Rightismight (talkcontribs) 04:39, 4 July 2014 (UTC)

I support removing this apparently speculative and uncited contribution. ~KvnG 14:02, 22 July 2014 (UTC)

Citation clean-up[edit]

The citation format for this article is a mess. The usual practice is to follow the format that was first introduced, which appears to be the APA style. Comments? Jc3s5h (talk) 17:49, 15 July 2014 (UTC)

Manually formatting references is not fun. I prefer to use {{citation}} and friends. ~KvnG 14:02, 22 July 2014 (UTC)