[LEAPSECS] next leap second

[Brooks Harris]

IERS Technical Note No. 36
IERS Conventions (2010)
ftp://tai.bipm.org/iers/conv2010/tn36.pdf

-Brooks

On 2017-01-12 01:08 PM, Brooks Harris wrote:
> On 2017-01-12 12:18 PM, Michael Shields via LEAPSECS wrote:
>> On Wed, Jan 11, 2017 at 5:03 PM, Warner Losh <imp at bsdimp.com> wrote:
>>> On Wed, Jan 11, 2017 at 3:28 PM, Zefram <zefram at fysh.org> wrote:
>>>> It would be nice to have more sophisticated projections from IERS more
>>>> than a year ahead.  It would particularly help in evaluating the 
>>>> proposals
>>>> that have been made involving scheduling leap seconds further ahead.
>>> Especially if they had error bars that reflect the current confidence
>>> levels, perhaps tested on historic data.
>> It might also be helpful if we understood better how these models are
>> used to decide when to announce leap seconds.
> As I understand it, it's pretty complicated. IERS is the top node in a 
> hierarchy of entities; there are many contributing organizations 
> including the participating observatories and interaction with BIPM. 
> The IERS conventions guide the procedures, and those are large and 
> complicated documents. It's a pretty big administrative and technical 
> apparatus. It would be nice to understand it better, but the bottom 
> line for practical timekeeping discussions seems to be the IERS products.
>
> Maybe someone can inform us better?
>
> -Brooks
>> I don't know currently
>> what criteria the IERS uses, except the overall parameters of keeping
>> |UT1-UTC| < 0.9 s and preferring to have leap seconds in June or
>> December instead of other months.
>>
>> For example, here's Bulletin A from 2016-06-30:
>>
>> https://datacenter.iers.org/eop/-/somos/5Rgv/getTX/6/bulletina-xxix-026.txt 
>>
>>
>> 2016-12-31 (MJD 57753): -0.45079 s
>> 2017-06-30 (MJD 57934): -0.73759 s
>>
>> You might have expected either of these days to have leap seconds.
>> The next week, Bulletin C Number 52 announced a leap second for
>> 2016-12-31.  The actual value of UT1-UTC on that day was about
>> -0.407858 s.
>>
>> The predictions looked similar on 2014-06-26:
>>
>> https://datacenter.iers.org/eop/-/somos/5Rgv/getTX/6/bulletina-xxvii-026.txt 
>>
>>
>> 2014-12-31 (MJD 57022): -0.46583 s
>> 2015-06-26 (MJD 57199): -0.67258 s
>>
>> Again, either December 2014 or June 2015 could have had leap seconds.
>> But in this case the leap second was deferred.  It happened on
>> 2015-06-30, when UT1-UTC was -0.6760362 s
>> (https://datacenter.iers.org/eop/-/somos/5Rgv/getTX/207/bulletinb-330.txt). 
>>
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