Jonathan,
I've got to disagree with you about your second and third responses
below. The calendar only specifies how the reference date and time are
to be interpreted. It says nothing about either the time variable values
or the decoding that should be used to turn those elapsed time values
into dates and times. That choice is entirely up to the data consumer.
If a data producer started with a set of Julian calendar dates and
created a time variable, and a data user prefers to use Proleptic
Gregorian dates, there is no problem. One is not more correct than the
other.
Grace and peace,
Jim
On 6/3/15 10:47 AM, Jonathan Gregory wrote:
Dear Chris
While not happy, would you agree to introduce gregorian_utc, gregorian_gps,
gregorian_nls, define gregorian = gregorian_nls and deprecate it?
seems reasonable to me.
Good.
I think we
should omit gregorian_tai (although it's been instructive to discuss it)
since it's not been asked for yet.
fine with me -- I don't need it :-) -- though I thought that was the start
of this entire discussion.
The title of the thread is GPS. But maybe it was TAI. Please could anyone who
needs TAI speak up!
so the Calendar is ONLY for defining the reference
timestamp in the units.
I don't agree still with this. The calendar specifies the time system for
the reference time-stamp and the decoded time-coordinates,
I'm confused -- in the file, there are ONLY encoded time on the time
coordinates. How it gets decoded is entirely up to the data user -- they
can put it any calendar they want. I suppose your point is that the data
provider is specifying how the time coordinate is intended to be used --
which is fine. I can't imagine it would cause any problems to think of it
that way.
Yes, that's what I meant. If the decoding is done as specified by the method
implied by the calendar, the timestamps are (a) correct for and (b) should be
interpreted as being in that calendar. As a result of this discussion I see
that (a) and (b) are not the same, but they belong together.
I have learned,
and it also specifies how the translation is done.
by whom? when? my point is that the translation is up to the data user --
it's not in the file.
By identifying the calendar, the data-producer is (a) stating the method
which was used to encode the time coordinates (b) instructing the data-user to
use the reverse of that method to decode them into timestamps.
Best wishes
Jonathan
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