[LEAPSECS] My FOSDEM slides

[Warner Losh]

> On Mar 6, 2015, at 9:57 PM, Steve Allen <sla at ucolick.org> wrote:
> 
> On Fri 2015-03-06T21:37:42 -0700, Warner Losh hath writ:
>> So it isn't outside the realm of possibilities that you'd have people making measurements
>> from the late 60's till 1972 using UTC (and yes, it did exist in a practical form
>> before 1972, just not in the current form and the common usage often leaves some
>> ambiguity between the actual, realized form as broadcast by WWV, or the proleptic
>> form w/o leap seconds). Actual measurements from this time, though, were based
>> on something approaching the UTC as broadcast by WWV. Not sure how many data
>> sets from that time survive until today, and how many need to be converted from that
>> to UT1 or UT2, but evidentially there's some...
> 
> Yes and yes, but these are specialty applications for specialty datasets
> which can only be reduced to a precise modern time scale if the original
> observations and equipment were meticulously calibrated.
> And then they must be reduced by going back to look at, e.g.
> https://plus.google.com/photos/112320138481375234766/albums/6078225731350227361

There are a few observatories around here (being in proximity to Boulder) that have
data from this time. They know it is only good to a millisecond or so, but that’s UTC
not UT. They don’t have to recreate the calibrations or whatever today because they
know the data isn’t much better than that. Still, there is some of it that it matters to. Though
maybe by now the old professors are gone and the data is too… My data on this is
about 15 years old, and even then it was second hand...

> Please don't try to make this part of a General Timestamp API.
> 
> Before 1972, for a general API, there is just UT.

Generally yes. I agree. For most data, UT is close enough, since that also required a lot
of specialty data that you have to look up in books if you want to covert it to elapsed time.
I’d make it be opt-in, but I wouldn’t make it impossible.

Warner
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