Hello R-user bug seekers are needed! In order to perform these simple tasks you have to use a copy of SPSS and obviously R. The problem is that date conversion of data coming from SPSS gives wrong results, if we follow ?as.POSIXct
## SPSS dates (R-help 2006-02-17) z <- c(10485849600, 10477641600, 10561104000, 10562745600) as.Date(as.POSIXct(z, origin="1582-10-14", tz="GMT")) Note that ?as.POSIXct is coherent with the SPSS 'Programming and Data Management' guide (pag. 116): 'Internally, dates and date/times are stored as the number of seconds from October 14, 1582, and times are stored as the number of seconds from midnight.' I think the SPSS 'Programming and Data Management' is not very clear: "times are stored as the number of seconds from midnight", but which midnight? 13th or 14th of October one? I think about 14th , so as.Date(as.POSIXct(z, origin="1582-10-14", tz="GMT")) has to be changed to as.Date(as.POSIXct(z, origin="1582-10-15", tz="GMT")) Test: ----- Let's create a vector of dates in SPSS and save it in C:\\date.sav DATA LIST / mydate (date). BEGIN DATA. 01/01/1960 11/07/1955 25/11/1962 08/06/1959 28-01-2003 15,03,03 1/1/1997 01-JAN-1998 END DATA. save outfile = "C:\\date.sav" /compressed. Now we use R: library(foreign) test.df <- read.spss("C://date.sav", to.data.frame=T) now following ?as.POSIXct test.df$newdate <- as.Date(as.POSIXct(test.df$MYDATE , origin="1582-10-14")) But if you take a look at the vector test.df$newdate you got: R.date = SPSS.date - 1 day Please confirm this! I would like to be sure that i didn't made mistakes (I've used SPSS 11 + R 2.8) If you come back to data, changing 14 to 15 test.df$newdate2 <- as.Date(as.POSIXct(test.df$MYDATE, origin="1582-10-15")) assures that R.date = SPSS.date > test.df MYDATE newdate newdate2 1 11903760000 1959-12-31 1960-01-01 2 11762496000 1955-07-10 1955-07-11 3 11995257600 1962-11-24 1962-11-25 4 11885875200 1959-06-07 1959-06-08 5 13263091200 2003-01-27 2003-01-28 6 13267065600 2003-03-14 2003-03-15 7 13071456000 1996-12-31 1997-01-01 8 13102992000 1997-12-31 1998-01-01 You got that, do you? It is needed to (eventually) ask clarifications about SPSS to Raynald Levesque (the author of SPSS 'Programming and Data Management' guide) and to submit a bug for ?as.POSIXct thank you Luca ______________________________________________ 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.