I've been having trouble following some of the language, and so I want to start by citing this snippet as a clear description of current practice:
On Apr 28, 2015, at 14:41, Jim Biard <jbiard at cicsnc.org> wrote:
> In the "real" world, we often start with UTC timestamps that have leap seconds accounted for, yet convert them to elapsed times using calculators that don't account for leap seconds. This can actually lead to elapsed time values that encode a time discontinuity and cannot be counted on to produce accurate differences between every pair of values.
Assuming I grok reality, I agree that the historical default for existing datasets is that the leap second handling has to be "unknown", as it all depends on the conversion software.
With this as my baseline, I am not sure how to interpret the following sentence:
On Apr 29, 2015, at 06:39, Jonathan Gregory <j.m.gregory at reading.ac.uk> wrote:
> it is likely that nearly all existing time values have been encoded *without* leap seconds, and therefore *not* UTC strictly.
Let me take an example: A sensor system has a GPS, and timestamps its data accordingly. As I understand it:
the GPS timestamp is using UTC; and
the UTC has included any leap seconds that have been added since leap seconds began. (Must be true, or GPS timestamps would be 16 seconds off, right?)
So it seems to me almost all observational time values have been encoded *with* leap seconds, and therefore *are* UTC.
Can Jonathan or others clarify what I've got wrong?
John
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Received on Wed Apr 29 2015 - 09:50:07 BST
