Thanks David, now I wonder how you can have as.Date() render the date using local time rather than UTC.
Andrew On Mon, Sep 13, 2010 at 12:08 PM, David Winsemius <[email protected]>wrote: > > On Sep 13, 2010, at 11:56 AM, Andrew Yee wrote: > > I'm trying to understand why as.Date() is converting a the modified date >> of >> a file from August 22 to August 23. >> >> foo <- file.info(file.to.process) >>> str(foo) >>> >> 'data.frame': 1 obs. of 10 variables: >> $ size : num 5.37e+09 >> $ isdir : logi FALSE >> $ mode :Class 'octmode' int 436 >> $ mtime : POSIXct, format: "2010-08-22 23:14:52" >> $ ctime : POSIXct, format: "2010-09-13 11:34:31" >> $ atime : POSIXct, format: "2010-09-09 15:42:00" >> $ uid : int 503 >> $ gid : int 503 >> $ uname : chr "ayee" >> $ grname: chr "ayee" >> >> as.Date(foo$mtime) >>> >> [1] "2010-08-23" >> >> In this case as.Date(foo$mtime) gives August 23. I would have expected >> August 22. >> > > You are pretty close to midnight. Probably a TZ issue. Check your locale > settings versus UTC/GMT. > > > dt <- as.POSIXct("2010-08-22 23:14:52") > > as.Date(dt) > [1] "2010-08-23" > > Happens to me too, but when its 23:14 here, (US-EDT) it's the next day in > Greenwich. The help page says: > "The last [POSIXct] is converted to days by ignoring the time after > midnight in the representation of the time in UTC." That is not entirely > clear to my reading, but I am forced to conclude that it means as.Date > returns the Date in UTC terms rather than in local terms. > > -- > David. > > >> Thanks, >> Andrew >> >> sessionInfo() >>> >> R version 2.11.1 Patched (2010-09-11 r52901) >> Platform: x86_64-unknown-linux-gnu (64-bit) >> >> locale: >> [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C >> [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8 >> [5] LC_MONETARY=C LC_MESSAGES=en_US.UTF-8 >> [7] LC_PAPER=en_US.UTF-8 LC_NAME=C >> [9] LC_ADDRESS=C LC_TELEPHONE=C >> [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C >> >> attached base packages: >> [1] stats graphics grDevices utils datasets methods base >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> [email protected] 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 > > [[alternative HTML version deleted]] ______________________________________________ [email protected] 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.
