[ntpwg] Further to the timestamping issue

[Marshall Eubanks]

Dear Dave;

Leapseconds are driven by torques at the core mantle boundary, which  
we cannot see directly
and basically have information about only through UT1 and LOD  
measurements. In practice, leap seconds cannot
be predicted much more than 6 months to a year in advance because of  
that.

AND, keep in mind that in the "jerk" seen around 1905 would have meant  
several _negative_ leap seconds in
one year, which would I am sure be a fun experience if repeated today.

Regards
Marshall



On Jun 19, 2008, at 2:36 PM, David L. Mills wrote:

> Rob,
>
> You imply a burning desire to predict leap events possibly years in
> advance. From the IERS bulletins I gather announcing leap seconds is
> somewhat of a black art and the announcements are only a few months in
> advance, depending on the DUT1 crossover. Also, the IERS can announce
> multiple bulletins even now should they choose; however, the time
> dissemination community has no means at present to announce more than
> one at a time. In fact, it is possible to announce more than one
> occasion in the NIST leapseconds file. Should that possibility  
> arise, I
> would be delighted to have NTP properly respond to them.
>
> Dave
>
> Rob Seaman wrote:
>
>> TSG wrote:
>>
>>> Do you have any idea of the cost of implementing a log management
>>> practice that will address multiple Leap Second's being added???
>>
>>
>> No, and neither do you.
>>
>> You are also jousting with a windmill. Nothing would stop Gambis from
>> announcing a leap second for December 2011 at the same time as a leap
>> second for June 2009. (Dates chosen randomly.) Each would be handled
>> in sequence whether or not NTP is aware of both at the same time.
>> This is precisely a feature of UTC that has been requested. The
>> question is how best would NTP implement it.
>>
>>> Considering also that Leap Second's are never added such that there
>>> would be more than one per month added,
>>
>>
>> Nice argument against leap hours :-)
>>
>>> the accidental adding of a leap second (assuming NTP automatically
>>> tracks them) could cause billions or trillions of dollars of damage
>>
>>
>> Somebody who places auditing above all other requirements might want
>> to actually characterize the cost/schedule/performance benefits and
>> risks of the various alternatives :-)
>>
>> Rob
>>
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>
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