Julian Date format -- interval not dateTime (my thought)

[Peter McCartney]

I guess the 'nominalDay' unit slipped past my notice. 

This question is drifting out of the datetime issue and into the count issue
which I don't think we ever resolved very well. To my recollection, counts
(and percents, etc) were not considered measurements by STMML and are all
dimensionless units. I don't think we are going to start naming units for
all the things we might count integer numbers of, are we? I would have
encoded day of the year as simply ratio with a unit of dimensionless and a
domain of 0 to 365. 

Peter McCartney (peter.mccartney at asu.edu)
Center for Environmental-Studies
Arizona State University
 


-----Original Message-----
From: Matt Jones [mailto:jones at nceas.ucsb.edu] 
Sent: Wednesday, March 19, 2003 9:58 AM
To: eml-dev at ecoinformatics.org
Cc: Henshaw, Don; Spycher, Gody
Subject: Re: Julian Date format -- interval not dateTime (my thought)


I agree.  We created the unit 'nominalDay' precisely for this purpose. It
represents an integer number of days.

Matt

Tim Bergsma wrote:
> Scott,
> 
> I was also wondering about "this advice".  I was taught somewhere not 
> to confuse Julian Day with day-of-year.  I use day-of-year, but I 
> don't really know what Julian Day is, and therefore hesitate to say 
> too much. With regard to "saying that something takes 200 Julian 
> Days", this is clearly the same concept as eml dictionary unit 
> nominalDay.
> 
> Tim.
> 
> Scott Chapal wrote:
> 
>>Was there ever any determination about Julian Day?
>>
>>What are we calling Julian Day in EML any way?
>>
>>YYYYddd or ddd ??
>>
>>David's numbers are what?  dddYYYY?
>>
>>Or does this advice pertain?  "The system of Julian days should not be 
>>confused with the simpler system of the same name which associates a 
>>date with the number of days elapsed since January 1st of the same 
>>year (according to which 2000-12-31 is day 366 of the year 2000)."
>>
>>Because the 'real' Julian Day is used in astronomy to number 
>>chronological days...
>>
>>So,
>>
>>ddd     - RATIO
>>YYYYddd - ORDINAL
>>
>>Or just other dateTime formats??
>>
>>-Scott
>>
>>David Blankman <dblankman at lternet.edu> writes:
>>
>>
>>>Don,
>>>
>>>I am not sure what the correct representation of Julian dates would 
>>>be. My sense is that the Julian date scale is actually an INTERVAL 
>>>scale not a dateTIME scale; arithmetic calculations are consistent, 
>>>that is, 2451919 - 2451819 gives the same value as 2351919 - 2351819. 
>>>It probably also makes sense to say that something that takes 200 
>>>julian days  = 2 * 100 julian days. My first thought was that it was 
>>>a ratio scale, but it is more like the celcius scale than the kelvin 
>>>scale in that the 0 on the julian scale is an arbitrary one.
>>>
>>>
>>>The julian date scale does not suffer from the problems that are 
>>>associated with a standard calendar scale, that is, the only unit is 
>>>the day and the fraction of a day; there is nothing like Feb 20 - Jan 
>>>20 representing a different number of days than Aug 20 - July 20.
>>
>>>I would appreciate enl-dev feedback on that.
>>>
>>>David
>>>
>>>Henshaw, Don wrote:
>>
>>>> On another topic:
>>>
>>>>Can a julian date be represented in the format string for 
>>>>measurementScale of datetime
>>>
>>>>i.e., YYYYddd
>>>> Other notes (being rather picky): pertaining to 
>>>>eml-unitDictionary.xml (2.0.0)
>>
>>--
>>\SEC
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> 
> 

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