
You can also make the change in the excel file first. 
 
In excel highlight the date column-> right click-> format cells ->under number tab click custom ->in the Type field type the following "yyyy-mm-dd"
 
Now save and import.
 

> Date: Fri, 5 Aug 2011 13:59:16 +0100
> From: ted.harding@wlandres.net
> To: r-help@r-project.org
> CC: emma.raven@jbaconsulting.co.uk
> Subject: Re: [R] excel dates and times in R
> 
> On 05-Aug-11 10:27:28, bevare wrote:
> > Hello,
> > I am having some fun dealing with dates and times. My input
> > is a excel csv file with two columns with data in the following
> > format: 
> > 
> > date time
> > 25-Jun-1961 04:00:00
> > 
> > i.e. day - month - year hour:min:sec
> > 
> > I would like to have a single object in R that combines these
> > and converts them into a sensible R format (e.g.
> > ISOdatetime(1961,06,25,04,00,00,tz="GMT").
> > 
> > I have played with the function chron and also strptime but
> > can't seem to get them to work. 
> > 
> > Can anybody help me out please? 
> > 
> > Thanks
> > Bevare
> 
> I know almost nothing about using the "time" functions in R,
> but since I see that I get:
> 
> ISOdatetime(1961,06,25,04,00,00,tz="GMT")
> # [1] "1961-06-25 04:00:00 GMT"
> 
> it would seem that you already have it almost made in the
> original Excel fields, namely:
> 
> paste("1961-06-25","04:00:00","GMT",sep=" ")
> # [1] "1961-06-25 04:00:00 GMT"
> 
> So you could write this as a function
> 
> getISOdt <- function(date,time,zone){
> paste(date,time,zone,sep=" ")
> }
> 
> where the parameters date, time and zone are supplied as
> character strings:
> 
> getISOdt("1961-06-25","04:00:00","GMT")
> [1] "1961-06-25 04:00:00 GMT"
> 
> Then you can apply() this to the two comlumns in the dataframe
> you get when reading in the Excel CSV file, with zone being
> supplied independently.
> 
> Hoping this helps,
> Ted.
> 
> --------------------------------------------------------------------
> E-Mail: (Ted Harding) <ted.harding@wlandres.net>
> Fax-to-email: +44 (0)870 094 0861
> Date: 05-Aug-11 Time: 13:59:14
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