[LEAPSECS] Time math libraries, UTC to TAI

[GERRY ASHTON]

> On December 29, 2016 at 6:00 PM Steve Allen <sla at ucolick.org> wrote, in part:
> 
> On Thu 2016-12-29T09:26:58 -0700, Warner Losh hath writ:
> 
> > How do you deal with acquiring knowledge of leap seconds after you've
> > given out 'old' timestamps that might be affected by them? This is
> > best described as how well you recover from the leapsecond file being
> > corrupted and replaced, though there's many other scenarios here.
> 
> This question is similar to the ones that the EU financial sector
> have been asking in the face of the ESMA MiFID II regulations that
> will require extremly precise timestamps on market trades.
> https://www.esma.europa.eu/sites/default/files/library/2015/11/2015-esma-1464_annex_i_-_draft_rts_and_its_on_mifid_ii_and_mifir.pdf
> 
> .
> 
> .
> 
> .
> 
> In some of the salepitches it has been evident that the answer to the
> MiFID II and Warner Losh's question is that companies exist who will
> install high-precision timestamping gear at the market and lease a
> direct connection to the nearest national metrology institute. Those
> salespitches also indicate that despite the use of term UTC in the
> text of the regulation, the underlying system will have to work in TAI
> (which I take that they are simplifying the sales pitch and they
> really mean a TAI-like timescale).
> 
> That way the initial trade timestamps will be a provisional local time.
> When the regulators come knocking on the door asking about the actual
> UTC of a transaction the provisional local time can be converted to
> a value of UTC consistent with BIPM.
> 
> And all that is the same technique that astronomers and navigators
> have used for centuries. The new part in all the above leaked
> information is that the way that timekeeping works has now been
> inculcated to financial market regulators.
> 

The principals of trades (sellers and buyers) are critically interested in the date in their local time zone on which a trade occurred. As an example, due to the percentage of income taken by income taxes being higher for higher incomes, there is a huge difference whether a stock sale with a profit of $50,000 occurs in 2018, when the seller's other income is $60,000, or 2019, when the seller's other income is $10,000. Therefore it is critical that the UTC time be reported to principals; it would not be acceptable to let the time scale reported to principals to differ by 36 seconds from the time scale recognized by tax authorities. So waiting until the regulators come knocking on the door would not be acceptable.