Rich gave a long response on this fact also, pointed out why months are
deprecated in CF and the problems it causes.
-Roy
On Apr 11, 2013, at 1:10 PM, Steve Hankin <steven.c.hankin@xxxxxxxx> wrote:
> Hi John, Patrick,
>
> Quick sleuthing. Looking at the OPeNDAP HTML page I see that the units of
> the time axis are "months since 1901-01-01 00:00:00"
>
> It's miraculous that the two interpretations differ by a mere 21 minutes out
> of a 50 year offset from T0, considering that "months" is not a standardized
> time unit. CF advises that "...the unit month ... should be used with
> caution". An understatement that might better be stated as (say) "units of
> months should not be used in any case where the desired precision in the
> specification of the date is finer than 1 day" (to be on the safe side).
>
> - Steve
>
>
>
> On 4/11/2013 11:30 AM, John Caron wrote:
>> Hi Patrick:
>>
>> So WMS datetimes are probably being done through ncWms, using Joda Time
>> library, whereas the TDS opendap service will not interpret the dates, so it
>> must be the ferret client, presumably using udunits C library.
>>
>> Its hard to imagine 2 date libraries getting different answers, but since
>> one is done on the server, and the other on the client, it must be the
>> difference in the gravitational attraction of the moon between the two
>> locations, causing a slight difference in the length of the month.
>>
>> Do you by any chance know what is the correct answer?
>>
>> John
>>
>>
>> On 4/9/2013 7:08 PM, Patrick Brockmann wrote:
>>> Hi all,
>>>
>>> I have a strange behaviour with time dimension values exposed by the
>>> GetCapabilities
>>> and values get from an OPeNDAP access.
>>> Could someone explain me what is the source of the problem ?
>>>
>>> http://webportals.ipsl.jussieu.fr/thredds/wms/CARBON/CARBONES_PRIOR_orchidee_hadgem2-es_historical_nosoc_co2_npp_monthly_1951_2004_yearmonmean_3.nc?service=WMS&version=1.3.0&request=GetCapabilities
>>>
>>>
>>> ---> 1951-07-16T12:12:04.339Z, ....
>>>
>>> And from the OPeNDAP access with ferret client, I get
>>>
>>> ferret
>>> yes? use
>>> "http://webportals.ipsl.jussieu.fr/thredds/dodsC/CARBON/CARBONES_PRIOR_orchidee_hadgem2-es_historical_nosoc_co2_npp_monthly_1951_2004_yearmonmean_3.nc";
>>>
>>> yes? sg/t/l=1:10 npp2
>>> GRID GTL2
>>> name axis # pts start end
>>> MYLON LONGITUDE 720mr 0E 0.5W
>>> LAT LATITUDE 360 r 89.75S 89.75N
>>> normal Z
>>> TIME TIME 54 r 16-JUL-1951 12:33 15-JUL-2004 09:01
>>>
>>> L T TBOX TBOXLO TSTEP (months)
>>> 1> 16-JUL-1951 12:33:59 12 14-JAN-1951 21:39:23 606.4526
>>> 2> 15-JUL-1952 18:23:11 12 15-JAN-1952 03:28:35 618.4526
>>> 3> 16-JUL-1953 00:12:23 12 14-JAN-1953 09:17:47 630.4526
>>>
>>> --> Note the difference between 1951-07-16T12:12:04.339Z and 16-JUL-1951
>>> 12:33:59
>>>
>>> My TDS version is Version 4.3.15 - 20121218.1126
>>>
>>> Regards
>>> Patrick
>>>
>>
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**********************
"The contents of this message do not reflect any position of the U.S.
Government or NOAA."
**********************
Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097
e-mail: Roy.Mendelssohn@xxxxxxxx (Note new e-mail address)
voice: (831)-648-9029
fax: (831)-648-8440
www: http://www.pfeg.noaa.gov/
"Old age and treachery will overcome youth and skill."
"From those who have been given much, much will be expected"
"the arc of the moral universe is long, but it bends toward justice" -MLK Jr.
