Not sure but perhaps this is related to bug PR#3646 reported in:
http://maths.newcastle.edu.au/~rking/R/devel/03b/0195.html --- Date: Thu, 4 Dec 2003 11:20:15 -0600 From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Subject: [R] bug in as.POSIXct ? I think that there is a bug in the as.POSIXct function on Windows. Here is what I get on Win2000, Pentium III machine in R 1.8.1. > dd1 <- ISOdatetime(2003, 10, 26, 0, 59, 59) > dd2 <- ISOdatetime(2003, 10, 26, 1, 0, 0) > dd2 - dd1 Time difference of 1.000278 hours Now, the 26th of October was the day that change to the standard time occurred, so I suspect that this has something to do with that. In fact > dd1 [1] "2003-10-26 00:59:59 Central Daylight Time" > dd2 [1] "2003-10-26 01:00:00 Central Standard Time" so it looks like the switch from CDT to CST happens at 1:00 (instead of 2:00 ?). Since the only thing the difftime function does is unclass the as.POSIXct values of its two arguments, the error seems to be in the as.POSIXct code. I looked at the C code of the as.POSIXct function but I do not know enough about R code and C handling of the time structures to find an error there. Perhaps, the error is actually in the C library handling of time structures on Windows machines. All this seems to work fine in version 1.8.1 patched 11-24 on a Linux machine, i.e. the above difference is 1second. However, the swicth between CDT and CSD also accurs at 1:00. Andy __________________________________ Andy Jaworski 518-1-01 Process Laboratory 3M Corporate Research Laboratory ----- E-mail: [EMAIL PROTECTED] Tel: (651) 733-6092 Fax: (651) 736-3122 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help