[LEAPSECS] the big artillery

[Brooks Harris]

On 2014-11-04 11:53 AM, Gerard Ashton wrote:
> Of course Brooks Harris is free to define proleptic UTC any way he pleases
> within the confines of a document he has control over, including a post to
> this mailing list. But I think the term "proleptic UTC", outside the
> confines of a document that gives it a proprietary definition, could mean a
> variety of things.

Sure, thanks. But using a name that elicits incoming projectiles isn't 
so helpful either. I'll conjugate on, or accept suggestions for, a 
better name.

> For example, the Standards of Fundamental Astronomy
> subroutine  iauDat provides the delta between TAI and UTC, and the source
> code comments say "UTC began at 1960 January 1.0 (JD 2436934.5) and it is
> improper to call the function with an earlier date."
For purposes of astronomy, and probably others, the "rubber band era" 
may have relevance. To call it "UTC" seems a bit of a stretch to me, but 
there's no generally accepted name for what Zefram calls "rubber-seconds 
era of UTC". Everybody has seized the name, and attempted to give it 
some meaning other than what I, at least, consider to be its origin - 
1972-01-01T00:00:00Z, when there was exactly 10 seconds initial TAI-UTC 
offset, and when Leap Seconds were deemed to exist. As we've heard so 
often here, the term doesn't appear until sometime late in the 
development of the timescale. POSIX seized on it, NTP, PTP, and here 
another organization has extrapolated it into the past.

>   In as much as UTC
> attempted to track UT2 in the 1960s, I would regard 1960 January 1.0 as the
> dividing point between proleptic UTC and UTC, and I would regard proleptic
> UTC as synonymous with UT2. If it turns out that creates a discontinuity at
> the dividing point, so be it.

That's one of the problems with "UTC", isn't it? Everybody seems to have 
a slightly different idea what it is.

-B

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