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DATETIME  December 2010

DATETIME December 2010

Subject:

Re: unknown/questionable/uncertain/approximate

From:

"Ray Denenberg, Library of Congress" <[log in to unmask]>

Reply-To:

Discussion of the Developing Date/Time Standards <[log in to unmask]>

Date:

Tue, 7 Dec 2010 14:18:18 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (197 lines)

Well Ed, thanks for all the fascinating information.  

I'd like to try to refocus on the issues at hand. I had felt last week that
we were starting to make progress and I would like to pick up from there,
perhaps propose a way forward with some compromise. 

To begin, let's distinguish:

(a) one unspecified date from a set of dates, 

from

(b) all of the dates in a set.

We already have proposed general syntax,  square and curly bracket for (a)
and (b) respectively.  

There is a further distinction necessary. In the case of "all the dates" and
let's say more specifically "all the years" and even more specifically than
that when they are consecutive - so lets say we have {1960,1961,1962,1963} -
this means in effect "all of the (discrete) years, 1960 through 1963".  It
DOES NOT mean "the (continuous) interval 1960 through 1963", and we need to
make that distinction. So an interval is a continous period, as opposed to a
set of consecutive dates. (Point is, when we use the curly brackets to
enclose a set of dates, they do not need to be consecutive, but if they are,
it does not constitute an interval; I think this has been a point of
confusion.)  

Having said all this as background,

I propose:

(1)  For a standard (continuous) interval with a start and end date, the ISO
notation (using "/" ) MAY be used, e.g. '1959/1971' means the continuous
period covering 1959 through 1971.
     Note: an interval has a start and end date, though one or the other may
be implicit, that is the interval may be specified by a start and duration
or a duration and end.

(2) As an alternative to (1) the double-dash notation may be used.  Thus
1959--1962 would also denote the continuous interval 1959 through 1962.  
   Notes: 
1.This is proposed because of objection raised by some to the '/' used in an
interval.
2. Double-dash is proposes rather than a single dash because single dash is
already used within dates.

(3) To denote "all of the (discrete) years 1959, 1960, ..., 1971" (as
opposed to the continuous interval in (1)), use curly brackets and the
double-dot notation, i.e. {1959..1971}.   commas may be used also, so
{1959..1961,1963} would mean "the years 1959, 1960, 1961, and 1963". {1961,
1963,1965..1967} would mean "the years 1961, 1963, 1965, 1966, and 1967".

(4) For a decade, as a special case of "all of the years", to denote all of
the years of a decade (as opposed to a single, unspecified year from the
decade), as an alternative to (1) and (2) the x notation may be used, e.g.
196x denotes all of the years of the 1960s (similary xx for all the years of
a century, etc.)  

(4) Square brackets means "one of the dates" using the double-dot and comma
syntax.  

(5) For the special case of a decade, where it is intended to denote "one
year, unspecified, within the decade" the 'u' notation may alternatively be
used. i.e. "196u" means one year, unspecified, within the 1960s.  
   Note: If the 'u' character in this usage is still offensive then we need
to continue to discuss an alternative character. But note that 'u' now
stands for "unspecified" not "unknown".

I would like feedback on these few proposals and then I will follow with
additional suggestions addressing terminology issues that we have been
discussing.

But please focus on these for the moment. 

--Ray


> -----Original Message-----
> From: Discussion of the Developing Date/Time Standards
> [mailto:[log in to unmask]] On Behalf Of Edward C. Zimmermann
> Sent: Monday, December 06, 2010 12:56 PM
> To: [log in to unmask]
> Subject: Re: [DATETIME] unknown/questionable/uncertain/approximate
> 
> On Thu, 2 Dec 2010 15:53:40 -0500, Ray Denenberg wrote
> > Ed - Your argument for 196u in favor of [1060....1969]  certainly
> > convinces me that I would rather use an analog than digital
> > thermometer if I am seeking accuracy and repeatability. And that I
> 
> Digital display technology makes them nearly always more readable than
> analog. This is the case for not just measure of temperature, weights
> and lengths but also time.
> 
> Early mass market battery powered digital clocks from Asia were
> notoriously inaccurate. While cheap mains powered clocks used the line
> frequency (50Hz or
> 60-Hz) these used little more than a simple RC-oscillator--- the first
> LED watch, the Pulsar, used a 32.768 Khz crystal or 2^15 but cost $1500
> USD in 1970--- and a counter. LCD made it possible for cheap driver
> circuits so there were even some cheap LCD stop-watches sold in the
> early 1980s that even offered 1/10th second readability. If anyone here
> recalls them they were extremely cheap (under $1 USD in Asia) but often
> lost (I seem to remember them always running slow) as much as 5 min.
> day (despite xtal).
> 
> 
> Compare now to the readability, repeatability and accuracy of a COSC
> certified
> chronometer: it can have, at best, 1 second readability but
> repeatability of better than +-5 seconds/day and accuracy better than
> +-10 seconds/day (which in the extreme case adds up 1 hour/year  365*10
> sec = 3650/60 min).
> 
> Many wristwatches don't have seconds hands and thus provide readability
> of only 1 minute. Some of these have good higher frequency xtal
> controlled (CMOS low power) movements and are are thus much more
> accurate than any COSC certified chronometer: accuracy up to +-1
> min/year (in other words accuracy and precision within a year are in
> the same units).
> 
> In 1967 the General Conference on Weights and Measures (CGPM) adopted
> the atomic definition of the second as the unit of time interval. The
> second is defined as the duration of 9192631770 cycles of radiation
> corresponding to the transition between two energy levels of the
> caesium-133 atom.
> 
> There used to be something called "Normed Railway Time" (Normalzeit).
> In Germany the national railway operated a system of clocks built
> around Lavet stepping motors (today the system is still in operation
> but is now driven by
> DCF77 radio, e.g. national time reference). These clocks were readable
> to 1 second. They were accurate (against their own reference) and
> repeatable to the speed to electricity to transfer the pulses which put
> it at under 1 second.
> 
> I've mentioned the Hebrew date/time system. Its  based upon an
> astronomical
> model: the motion of the Sun. While the Babylonians had a concept of
> "seconds"
> and sub-seconds (dividing things) the Babylonians measured (and
> reported time) using a double-hour lasting 120 modern minutes, a time-
> degree lasting four modern minutes, and a barleycorn lasting 3 1/3
> modern seconds. One could talk about 1/60th of a barleycorn but there
> was no means to measure it.
> 
> This brings us back to the origin of precise and accurate modern second
> measurements. This can be credited to Huygens who first suggested the
> use of a pendulum, viz. the linkage of time with the force of gravity
> (constant at any given spot on the planet).
> 
> 
> What we have now is gravity, decay of caesium-133 and the motion of the
> Sun across the Meridan.. AND we have measurement of time given my
> people against some reference clock near an event.. e.g. 1865-05-
> 15T7:22 Washington DC time for the death of Lincoln.
> 
> 
> In Judaism there is even geospatial issues for some date/events. Purim,
> for example, is celebrated in all places that were surrounded by walls
> at the time of Yehoshua as in Shushan (Susa, Iran) on 14 Adar and
> elsewhere on the
> 15 Adar. Thus in Jerusalem Purim is 14 but elsewhere the 15th. To
> distinguish the two one can speak of Purim De'Prazot and Purim
> De'Mukafot but generally the indication of day, 14 or 15, is implicitly
> set by the location of either the speaker or listener in Jerusalem.
> 
> I've been talking about measuring the current time. Going the other
> way..
> We often measure the age of things in the lab using Radiocarbon dating.
> The interesting thing about carbon dating is that its level of
> uncertainty is relatively low and does not increase linearly in time.
> The precision of a radiocarbon date is within a few hundred years.
> 
> Like the doctors noting what they assume to be the date/time of of
> Lincoln's death we also have for Biblical events a chronology specified
> in the Torah.
> The Torah gives us dates with much higher precision than Radiocarbon
> dating and the Torah itself can be calculated as being "given" on Mount
> Sinai 3323 years ago.
> 
> We have another form of dating which I'll call empirical dating. Its
> relevant to bibliographic recording. One does not know when, in fact,
> something was published but makes a good "educated guess" with a
> scientific consensus. These dates are not "questionable".. but they may
> change (in contrast to dates determined by Biblical chronology) as new
> states of information and knowledge emerge.
> 
> We will now agree that also for time systems we have differences in
> readability, repeatability and accuracy and that higher readability
> does not mean higher repeatability nor repeatability mean accuracy--
> which itself is really a measure against a reference (and includes its
> own model or
> paradigm)--- etc.
> 
> 

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