[time-nuts] LSEM (Leap Second Every Month)

Fri Jul 22 21:44:51 UTC 2016

Hi Brooke,

About sundials, timezones and "precise" timekeeping ...

There's a wonderful map by Stefano Maggiolo that everyone should look at:
http://blog.poormansmath.net/images/SolarTimeVsStandardTime.png

"How much is time wrong around the world?"
http://blog.poormansmath.net/how-much-is-time-wrong-around-the-world/

Someone mentioned the effect of leap seconds on true solar time. Based on the map, it's pretty common for civil noon (based on UTC) to be as much as an hour or more different from solar noon. Part of that is timezones. Part of that is DST. Part of that is seasonal, as in the equation of time (EoT). Given that, a +/-1 second offset due to a leap second is lost in the noise. In fact according to my EoT calculator the offset for today is 300 s and tomorrow its 309 s. So even one day's worth of EoT is ten times more than a leap second.

I would be interested in Sun dials too, maybe even a solar disciplined oscillator (SoDO), except most weeks it would be in holdover mode up here in the Northwest. ;-) The PID code would be quite interesting, since you can forward predict EoT. I think this is something Mike Cook would want to build, yes?

One other calculation for you: Earth circumference is 40,000 km. At 45 degrees latitude it's cos(45) = 0.707 as much. So an hour error from noon is 700 miles; a minute is 12 miles; a second is 1000 feet; and 1 ms is 1 foot; just like the speed of sound. That means a leap second is equivalent to walking 1000 feet, while DST is being forced marched 700 miles.

/tvb

----- Original Message ----- 
From: "Brooke Clarke" <brooke at pacific.net>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Friday, July 22, 2016 12:16 PM
Subject: Re: [time-nuts] LSEM (Leap Second Every Month)

> Hi Tom:
> 
> One of my interests is in Sun dials, so I like the idea of civil time corresponding as close as possible to the Sun's 
> position. Heliochronometers can be accurate to some seconds.
> The Dent <http://www.prc68.com/I/Dent.shtml>Dipleidoscope <http://www.prc68.com/I/Dent.shtml> was used to set railroad 
> clocks based on the Sun's position.
> 
> Another area of interest is astronomy where UTC1 adds a correction to a tenth of a second to UTC that essentially 
> bridges the gap between the leap second corrections.
> It would be interesting to learn how the Software Bisque Paramount telescope mount handles time.  It does not have any 
> provision for a time nuts oscillator/clock, but maybe should?
> 
> -- 
> Have Fun,
> 
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> The lesser of evils is still evil.
> 
> -------- Original Message --------
>>> If UTC time was adjusted every month would stick with one full second? Or
>>> some smaller quantity?
>> Hi Scott,
>>
>> The LSEM month suggestion retains the UTC policy of leaps being exactly +1 or -1 second, never larger, never smaller.
>>
>> There's a world of hurt if anyone even dreamed of shifting UTC by a fraction of a second. In fact, one of the main reasons UTC was created in the 70's was to put an end to the dreaded fractional jumps in atomic timekeeping during that era. Fractional steps atomic frequency and fractional steps in atomic time were both tried during 60's. For example:
>>
>> http://www.leapsecond.com/history/wwvb1966.htm
>>
>> Eliminating frequency jumps completely (by defining the UTC second to be 9,192,631,770 Hz cesium), and
>> changing any steps to be full +1 or -1 second integers (and not fractions) was why UTC was created.
>>
>> /tvb
>>
>> ----- Original Message -----
>> From: "Scott Stobbe" <scott.j.stobbe at gmail.com>
>> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
>> Sent: Thursday, July 21, 2016 3:06 PM
>> Subject: Re: [time-nuts] LSEM (Leap Second Every Month)
>>
>>
>>> If UTC time was adjusted every month would stick with one full second? Or
>>> some smaller quantity?
>>>
>>> On Thursday, 21 July 2016, Brooke Clarke <brooke at pacific.net> wrote:
>>>
>>>> Hi Tom:
>>>>
>>>> I like this idea.  I addresses the lesson from Y2K that something done
>>>> often works much better than something done only occasionally.
>>>> That's way you see the firetruck at the local store, because it's used all
>>>> the time and so is more likely to work when needed.
>>>>
>>>> --
>>>> Have Fun,
>>>>
>>>> Brooke Clarke
>>>> http://www.PRC68.com
>>>> http://www.end2partygovernment.com/2012Issues.html
>>>> The lesser of evils is still evil.
>>>>
>>>> -------- Original Message --------
>>>>
>>>>> Hi Tom...
>>>>>
>>>>> Does your proposal allow for a Zero leap second, or does it require
>>>>> either plus or minus 1 to work? Seems like you could stay closer to the
>>>>> true value if you also have a zero option. Might also cause less
>>>>> consternation for some services, like the finance and scientific worlds,
>>>>> that seem to have critical issues when an LS appears.
>>>>>
>>>>> I like your point that by having it occur monthly it forces systems to
>>>>> address issues promptly, and maybe that's the argument for the non-zero
>>>>> option.
>>>>>
>>>>> Tom Holmes, N8ZM
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Tom Van
>>>>> Baak
>>>>> Sent: Thursday, July 21, 2016 1:28 PM
>>>>> To: Discussion of precise time and frequency measurement <
>>>>> time-nuts at febo.com>
>>>>> Cc: Leap Second Discussion List <leapsecs at leapsecond.com>
>>>>> Subject: Re: [time-nuts] Leap second to be introduced at midnight UTC
>>>>> December 31 this year
>>>>>
>>>>> Time to mention this again...
>>>>>
>>>>> If we adopted the LSEM (Leap Second Every Month) model then none of this
>>>>> would be a problem. The idea is not to decide *if* there will be leap
>>>>> second, but to force every month to have a leap second. The IERS decision
>>>>> is then what the *sign* of the leap second should be this month.
>>>>>
>>>>> Note this would keep |DUT1| < 1 s as now. UT1 would stay in sync with
>>>>> UTC, not so much by rare steps but by dithering. There would be no change
>>>>> to UTC or timing infrastructure because the definition of UTC already
>>>>> allows for positive or negative leap seconds in any given month.
>>>>>
>>>>> Every UTC-aware device would 1) know how to reliably insert or delete a
>>>>> leap second, because bugs would be found by developers within a month or
>>>>> two, not by end-users years or decades in the future, and 2) every
>>>>> UTC-aware device would have an often tested direct or indirect path to IERS
>>>>> to know what the sign of the leap second will be for the current month.
>>>>>
>>>>> The leap second would then become a normal part of UTC, a regular monthly
>>>>> event, instead of a rare, newsworthy exception. None of the weird bugs we
>>>>> continue to see year after year in leap second handling by NTP and OS's and
>>>>> GPS receiver firmware would occur.
>>>>>
>>>>> Historical leap second tables would consist of little more than 12 bits
>>>>> per year.
>>>>>
>>>>> Moreover, in the next decade or two or three, if we slide into an era
>>>>> where average earth rotation slows from 86400.1 to 86400.0 to 86399.9
>>>>> seconds a day, there will be zero impact if LSEM is already in place.
>>>>>
>>>>> /tvb
>>>>>
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