On 2014-01-17 10:49 PM, Ian Batten wrote:
On 18 Jan 2014, at 01:22, Zefram <zef...@fysh.org> wrote:
Brooks Harris wrote:
Yes, I understand that. Perhaps using the word "origin" was careless.
Maybe you can suggest a better term.
"proleptic". You may usefully add "with astronomical year numbering" to
make clear that zero and negative year numbers are valid. But really,
when you're defining a time scale, the calendar is irrelevant. It's a
separate concern that should be addressed separately.
Of course the idea is that dates after 1972-01-01T00:00:00Z are
"earth corrected" (Leap Seconds).
Are you implying that dates before are not? That wouldn't be a proleptic
UTC.
Can someone suggest an application for a proleptic UTC representing dates in
the distant past
such that the differences between it and, say, proleptic UT1, proleptic TAI or
proleptic GPS
time would be significant, and where the issues would be common to some other
application?
Outside the production of historical astronomical data, where I suspect they
are going to
want a timescale which reflects variations in day length anyway, it's hard to
think of
applications where the recorded timestamps have precision better than the
differences between
these various putative timescales.
The purpose of the timescale I've suggested is accurate time-keeping
after 1972. The "proleptic UTC" (and it may need a different name) I've
tried to describe is an artificial construction for computational
convenience with defined relation to NTP, POSIX, and 1588/PTP. Its not
intended to be accurate before 1972.
On the other hand, a proleptic UTC with adjustments into the deep past
might be useful for, say, nit-picking historians, maybe the carbon
dating crowd. Interesting, but I wasn't trying to solve such problems,
if they exist.
-Brooks
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