[R] Serial Date

[David Winsemius]

On Mar 15, 2011, at 2:17 AM, Raoni Rosa Rodrigues wrote:

> Hello Mr. Allan and Mr. David!
>
> Thanks very much for your time and lessons.
>
> Works pretty well, Mr. Allan, specially after Mr. David explanation  
> (and the 2 days-bug correction).
>
> Just a curious behavior of data tranformation: the R-transformation  
> date was 2min and 20s late compared with excel 2007 time. Did you  
> know why?

I do not. One hypothesis might be that it relates to different  
treatment of the accumulation of leap-seconds:

http://en.wikipedia.org/wiki/Leap_second

Just a theory.

-- 
David.
>
> Attached a file with more than 1800 date-time values, that I used to  
> compare data. I ran this code on R
>
> Data = function (x){
>     c (ISOdatetime (1900, 1, 1, 0, 0, 0) + ((x-2)*60*60*24))
>     }
>
> and pasted result on excel where I compared with date time  
> personalized format (YYYY/MM/DD HH:MM:SS) of excel of original file.
>
> When I used a corrected code
>
> Data = function (x){
>     c (ISOdatetime (1900, 1, 1, 0, 2, 20) + ((x-2)*60*60*24))
>     }
>
> worked pretty well.
>
> Thanks again!
>
> All best,
>
> Raoni
>
> --- Em seg, 14/3/11, David Winsemius <dwinsemius at comcast.net>  
> escreveu:
>
> De: David Winsemius <dwinsemius at comcast.net>
> Assunto: Re: [R] Serial Date
> Para: "Allan Engelhardt" <allane at cybaea.com>
> Cc: "Raoni Rosa Rodrigues" <raonirosa at yahoo.com.br>, "R Help" <r-help at r-project.org 
> >
> Data: Segunda-feira, 14 de Março de 2011, 13:00
>
>
> On Mar 14, 2011, at 6:36 AM, Allan Engelhardt wrote:
>
>>
>>
>> On 14/03/11 02:00, Raoni Rosa Rodrigues wrote:
>>> Hello R Help,
>>>
>>> I'm working in a project with a software that register date and  
>>> time data in serial time format. This format is used by excel, for  
>>> exemple. In this format, 40597.3911423958 is 2011/2/23 09:23:15.
>>
>> Not on my system,
>
> Because ... There is a reasonably well understood MS bug in how it  
> handles the non-existent 1900-02-29. (It _still_ accepts that as a  
> valid date and calls it 60. I just re-demonstrated this amazingly  
> persistent bug behavior on the Mac Excel 2011 variant.  )
>
> http://finzi.psych.upenn.edu/R/library/cxxPack/html/serialNumber.html
> http://finzi.psych.upenn.edu/R/Rhelp02/archive/22942.html
>
> (I don't think Gabor's speculation regarding the migration from  
> Windows Excel to Mac Excel is possibly correct since Excel was  
> introduced on the Mac years before Windows was even a crash-prone  
> GUI on top of MS-DOS. The claim on one MS page is that the bug  
> originated in Lotus 1-2-3 and was emulated by Multiplan for  
> compatibility. )
>
> --David.
>
>
>
>> but this should get you going:
>>
>> ( a<- as.POSIXct("2011-02-23 09:23:15.00001", tz="GMT") )
>> # [1] "2011-02-23 09:23:15 GMT"
>> ( b<- difftime(a, ISOdatetime(1900,1,1,0,0,0), tz="GMT",  
>> units="days") )
>> # Time difference of 40595.39 days
>> as.double(b)
>> # [1] 40595.39
>> options("digits.secs" = 6)
>> ISOdatetime(1900, 1, 1, 0, 0, 0) + 40597.3911423958*60*60*24 # TZ  
>> dependent
>>> [1] "2011-02-25 09:23:14.702997 GMT"
>>
>>
>>
>> Hope this helps a little.
>>
>> Allan
>>
>>>   First part is number os days since 1900/1/1, and second part is  
>>> a fraction of a day.
>>>
>>> I need to make this transformation in R, and use it to make some  
>>> algebrian operations. I found that function 'serialNumber' of  
>>> package 'cxxPack' transform a as.data class object in this format,  
>>> but without time fraction. But I can't find nothing to do the  
>>> inverse way, transform serial date format in a POSIX class, for  
>>> exemple.
>>>
>>> Since now, thanks for your time and atention.
>>>
>>> All best,
>>>
>>> Raoni
>>> Associate Researcher
>>> Fish Passage Center
>>> UFMG, Brazil.
>>>
>>>
>>> "Fica proibido o uso da palavra liberdade,
>>>
>>> a qual será suprimida dos dicionários
>>>
>>> e do pântano enganoso das bocas.
>>>
>>> A partir deste instante
>>>
>>> a liberdade será algo vivo e transparente
>>>
>>> como um fogo ou um rio,
>>>
>>> e a sua morada será sempre
>>>
>>> o coração do homem."
>>>
>>> (Thiago de Mello)
>>>
>>>
>>>
>>>     [[alternative HTML version deleted]]
>>>
>>>
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>
>>     [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
>
> David Winsemius, MD
> West Hartford, CT
>
>
> <DateTime.txt>

David Winsemius, MD
West Hartford, CT