Hi Ben and Josh, No, I don't think that there is a bug. It's just due to my lack of knowledge on Date class, I was simply amazed that it has the daylight saving time built in at first. But on the second thought, it really should.
Thank you all for the explanations! ...Tao From: Ben Bolker <bbol...@gmail.com> To: "Shi, Tao" <shida...@yahoo.com> Cc: "r-h...@stat.math.ethz.ch" <r-h...@stat.math.ethz.ch> Sent: Saturday, October 30, 2010 7:22:04 AM Subject: Re: [R] date calculation On 10-10-30 02:02 AM, Shi, Tao wrote: > Hi Ben, > > That must be the case! In fact if I do: > >> difftime(strptime("24NOV2004", format="%d%b%Y"), >> strptime("13MAY2004",format="%d%b%Y"), units="days", tz="GMT") > Time difference of 195 days > > > which supports your claim. > > Can someone from the R development team confirm this? > > Thanks! > > ...Tao > > It sounds like you think this is a bug. It's not (although it's arguably not what you want). The general advice when using dates and time in R is to use the *least* specific date format that will do what you want, i.e. don't use a format that incorporates time zone information (daylight savings time) information if you don't want to deal with these complexities. I would suggest the chron package: library(chron) diff(chron(dates.=c("24/11/2004","13/05/2004"),format="d/m/y")) > > > > ----- Original Message ----- >> From:Ben Bolker <bbol...@gmail.com> >> To:r-h...@stat.math.ethz.ch >> Cc: >> Sent:Friday, October 29, 2010 7:54:53 PM >> Subject:Re: [R] date calculation >> >> >> Shi, Tao <shidaxia <at> >> href="http://yahoo.com">yahoo.com> writes: > >> Could someone >> explain to me why the following result is not a integer? >> >>> >> difftime(strptime("24NOV2004", format="%d%b%Y"), strptime("13MAY2004", >> >>> format="%d%b%Y"), units="days") >> Time difference of 195.0417 >> days > > Presumably because this goes across a daylight-savings >> time > adjustment? 0.0417=1/24 days is 1 hour ... > > Ben >> Bolker > > ______________________________________________ > >> ymailto="mailto:R-help@r-project.org" >> href="mailto:R-help@r-project.org">R-help@r-project.org mailing list > >> href="https://stat.ethz.ch/mailman/listinfo/r-help" target=_blank >>> 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@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.