[R] Convert number to Date

[Joshua Wiley]

Dear Anna,

Rolf's explanation not withstanding, it has to do with differences in
how R and Excel treat dates.  If you use

as.Date(40182, origin="1899-12-30")

you will get the same date as Excel.  You can look at:

http://office.microsoft.com/training/training.aspx?AssetID=RC102786151033&CTT=6&Origin=RP102786121033

For an official guide on how Excel dates are calculated.  Apparently,
Excel's calendar starts on 1 January 1900.  Why one has to use an
origin of 30 December 1899 in R...well, I suspect that gets back to
Rolf's explanation.


HTH,

Josh

On Thu, Mar 25, 2010 at 1:33 PM, anna <lippelanna24 at hotmail.com> wrote:
>
> Hello, I have a date value in excel: 1/4/2010 which in number format gives me
> 40182. When I read this with read.xls from R I get same 40182 so what I do
> is that I use the as.Date() function but here is what the as.Date() function
> returns me:
>> as.Date(40182)
> [1] "2080-01-06"
> Why don't I get the same thing as in excel?
> Thanks!
>
> -----
> Anna Lippel
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-- 
Joshua Wiley
Senior in Psychology
University of California, Riverside
http://www.joshuawiley.com/