Talk:Leap second

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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 (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.]


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)

Fake screenshot[edit]

Showing 23:59:60 when there's still more than two hours to go! — Preceding unsigned comment added by (talk) 21:57, 30 June 2015 (UTC)

Indeed not serious because people looking are misinformed about the time it happens. — Preceding unsigned comment added by (talk) 22:16, 30 June 2015 (UTC)

Future of the leap second.[edit]

This source [1] seems to indicate to me that no decision was made at the 2015 conference WRC-15 to abolish the leap second although it was resolved to look at this possibility. Are there any secondary sources confirming this? What should we say about the subject in the article? Martin Hogbin (talk) 12:49, 14 November 2015 (UTC)

My impression is the conference is still in progress. The document cited by Martin Hogbin seems to me to just repeat the resolution from 2012 to consider the matter at this year's conference; it seems more like an agenda item than a decision. Jc3s5h (talk) 20:55, 14 November 2015 (UTC)
I have had another read and I think you are correct. Do we know when the decision is likely to be made? Martin Hogbin (talk) 13:29, 15 November 2015 (UTC)
I recall that the conference is to end near the end of November. Jc3s5h (talk) 18:16, 15 November 2015 (UTC)
This mailinglist thread states that the proposal to eliminate them is dead for now. —Steve Summit (talk) 17:22, 19 November 2015 (UTC)
Whoops! But now this mailinglist thread cites this reasonably definitive-looking press release. I'll update the article unless someone beats me to it. —Steve Summit (talk) 17:25, 19 November 2015 (UTC)

Negative Leap Seconds[edit]

I added a note about negative leap seconds which was quickly reverted by AstroLynx. The comment given was “discussing (negative) leap seconds before 1972 does appear to be useful here”. Where else but in an article on leap seconds would one discuss negative leap seconds? In order to avoid an edit war I am asking for a discussion. John Sauter (talk) 14:36, 18 May 2016 (UTC)

The practice of leap seconds was only introduced in 1972. What is the use of discussing leap seconds before 1972? AstroLynx (talk) 16:54, 18 May 2016 (UTC)
My intent is to correct this sentence: “However, negative leap seconds have never been needed since the UTC standard was established, and are highly unlikely to ever be.” First, the UTC standard was established earlier than 1972, but did not include leap seconds until 1972. Correcting this would result in “However, negative leap seconds have never been needed since leap seconds started in 1972, and are highly unlikely to ever be.” The second problem is that “are highly unlikely to ever be” is a judgment not supported by any reference. It would be adequate to simply remove it, but I tried to do better by mentioning that in the recent past (1885) the rotation rate of the Earth would have required a negative leap second if leap seconds had existed. John Sauter (talk) 17:14, 18 May 2016 (UTC)
Such a discussion could be useful further down in the article. The opening paragraph of this article is already rather long and should not be burdened with too much information. There might be a problem however with the source which you propose to add as it seems to be mainly based on WP:OR. AstroLynx (talk) 10:41, 19 May 2016 (UTC)
Would it be acceptable to delete the offending sentence, and add a section on negative leap seconds? Perhaps it would be better to move all but the first paragraph pf the lead into the body, change Insertion of Leap Seconds to Scheduling of Leap Seconds, and add subsections on positive and negative leap seconds. John Sauter (talk) 00:31, 20 May 2016 (UTC)
I support removing the sentence from the lead. The second paragraph of the lead is pretty thick if anyone wants to do some additional trimming. Scheduling of leap seconds seems like an improved title for the second section. The end of this section would be a good place to mention negative leap seconds because the next section is Slowing of the Earth. I don't think subsections are necessary to cover negative and positive. ~Kvng (talk) 14:02, 24 May 2016 (UTC)

Since the Earth is slowing down (and I do not think it would be too hard to find references for this), the unlikeliness of negative leap seconds is quite obvious. C.f. the graph in the article ΔT. — Edgar.bonet (talk) 19:06, 19 May 2016 (UTC)

As I read the graph of LOD in this article, the Earth was completing a rotation in less than 86,400 seconds as recently as 2005. Looking at the graph you mentioned, notice that to obtain a negative leap second doesn't require that the graph go back to 0, but only that it slopes downward for a while. I don't think it is unreasonable to imagine that the Earth might speed up again in the next few decades, and next time it might be enough to cause a negative leap second. John Sauter (talk) 00:39, 20 May 2016 (UTC)

You are right, a negative leap second is not completely unreasonable. But the secular deceleration only makes it less and less likely. This deceleration is not visible in the LOD graph of this article, as it covers too short a time span. It is more obvious in the ΔT graph. — Edgar.bonet (talk) 09:58, 20 May 2016 (UTC)

In the long run, the Earth is slowing down. 3000 years ago, a positive leap second would have been completely unreasonable, and 3000 years from now, a negative leap second will be completely unreasonable. Today, however, both are within the realm of possibility. John Sauter (talk) 01:10, 21 May 2016 (UTC)

Notwithstanding the discussion of negative leap seconds here on the talk page, which concluded that negative leap seconds are possible, though unlikely, an editor has modified the article to say that negative leap seconds are not possible. I deleted the sentence in the lead that characterizes the likelihood of negative leap seconds. John Sauter (talk) 20:41, 21 May 2016 (UTC)