[LEAPSECS] Time Synchronization in Financial markets

[Brooks Harris]

Hi John,
On 2016-10-09 12:41 PM, John Sauter wrote:
> On Sat, 2016-10-08 at 15:58 -0600, Warner Losh wrote:
>> On Sat, Oct 8, 2016 at 2:43 PM, Steve Allen <sla at ucolick.org> wrote:
>>> On Fri 2016-10-07T11:48:25 -0600, Warner Losh hath writ:
>>>> Accurate, Traceable, and Verifiable Time Synchronization for
>>>> World
>>>> Financial Markets
>>>>
>>>> http://nvlpubs.nist.gov/nistpubs/jres/121/jres.121.023.pdf
>>>>
>>>> Market synchronization requirements today are 1s. However, in
>>>> August
>>>> 2017 they become 50ms. Good thing normal market hours on the US
>>>> exchanges avoids the leap second...
>>> Notably missing in this document is any mention of the term leap
>>> second.
>>> More surprising is no mention of TAI, despite the numerous
>>> references
>>> to the use of IEEE 1588 PTP for the timing systems.
>>> It's like getting a tour map that describes the route but fails to
>>> mention that along the way there's a bridge out.
>> Yes, it's like all the other systems I worked on that required
>> external UTC to be correct at all times, even when the GPS receiver
>> doesn't yet know the current number of leap seconds. I'll have to
>> pass
>> the leap second comment along to the author...
>>
>> Warner
> I took the lack of mention of leap seconds to mean that leap seconds
> ere not a problem.  The output of the NISTDC units is an astonishingly
>   accurate 1 pulse per second.  That feeds NTP, which handles leap
> seconds using a table.  As long as the table is kept up to date,
> everyone agrees on each second's name.
Except the one to be called YYYY-MM-DDT23:59:60.

There are 86401 pegs in the (positive) Leap Second UTC day. There are 
86400 holes in traditional timescales in which to put them. Something 
has to to go missing - the mapping is indeterminate. Common practice of 
introducing Leap Seconds on local timescales simultaneous with its 
introduction at UTC places these indeterminate labels at different 
time-of-day points along each local timescale. Non standardized and 
politically driven Daylight Savings rules further complicates when these 
indeterminate moments occur. Meantime there is no standardized way to 
keep the Leap Second tables automatically updated to begin with.

-Brooks
>      John Sauter (John_Sauter at systemeyescomputerstore.com)
>
>
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