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

Bob Camp kb8tq at n1k.org
Thu Jul 21 23:47:40 UTC 2016


Hi

A leap millisecond …. there’s an idea to explain to grandma. If you accept the idea that 
we need a leap second ever year or three, it’s not going to be a millisecond. Something 
messy would be required if you went below 100 ms. 100 ms would (barely) accommodate 
a “once a year” leap second. If it was a 0.1 sec event, you would not get the nice “back and forth” 
process for debugging and testing systems quite as often. 

Bob

> On Jul 21, 2016, at 6:06 PM, Scott Stobbe <scott.j.stobbe at gmail.com> wrote:
> 
> 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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