[R] Difference in numeric Dates between Excel and R

[David Scott]

On 2/03/2011 12:31 p.m., Nordlund, Dan (DSHS/RDA) wrote:
>> -----Original Message----- From: r-help-bounces at r-project.org
>> [mailto:r-help-bounces at r- project.org] On Behalf Of Luis Felipe
>> Parra Sent: Tuesday, March 01, 2011 3:07 PM To: r-help Subject: [R]
>> Difference in numeric Dates between Excel and R
>>
>> Hello. I am using some dates I read in excel in R. I know the
>> excel origin is supposed to be 1900-1-1. But when I used as.Date
>> with origin=1900-1- 1 the dates that R reported me where two days
>> ahead than the ones I read from Excel. I noticed that when I did in
>> R the following:
>>
>>> as.Date("2011-3-4")-as.Date("1900-1-1")
>> Time difference of 40604 days
>>
>> but if I do the same operation in Excel the answer is 40605. Does
>> anybody know what can be going on?
>>
>
> I think so.  It is a known problem that Excel thinks 1900 was a leap
> year, but it was not.  So Excel counts an extra day (for nonexistent
> Feb 29, 1900).  In addition,  Excel considers "1900-01-01" as day 1,
> not day 0.
>
> Hope this is helpful,
>
> Dan

An explanation which seems reasonably authoritative is given here:
http://www.cpearson.com/excel/datetime.htm


David Scott
>
> Daniel J. Nordlund Washington State Department of Social and Health
> Services Planning, Performance, and Accountability Research and Data
> Analysis Division Olympia, WA 98504-5204
>
>
> ______________________________________________ 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 Scott	Department of Statistics
		The University of Auckland, PB 92019
		Auckland 1142,    NEW ZEALAND
Phone: +64 9 923 5055, or +64 9 373 7599 ext 85055
Email:	d.scott at auckland.ac.nz,  Fax: +64 9 373 7018

Director of Consulting, Department of Statistics