Hello, I at first thought this was a system or locale issue, but since it occurs on both Windows and Linux and only for 2004 (AFAIK) I report it.
I have a problem with as.POSIXct for the hour between "2004-10-03 02:00:00 GMT" and "2004-10-03 02:59:59 GMT". In short, the 2 AM (GMT) hour in 2004 (but not in other years) is interpreted as 1 AM by strptime: (I use ISOdatetime as a convenience). ## Windows XP ISOdatetime(2004, 10, 3, 2, 0, 0, tz = "GMT") ##[1] "2004-10-03 01:00:00 GMT" ISOdatetime(2004, 10, 3, 1, 0, 0, tz = "GMT") ##[1] "2004-10-03 01:00:00 GMT" ISOdatetime(2005, 10, 3, 2, 0, 0, tz = "GMT") ##[1] "2005-10-03 02:00:00 GMT" ISOdatetime(2005, 10, 3, 1, 0, 0, tz = "GMT") ## [1] "2005-10-03 01:00:00 GMT" I've not explored it for other years, but it is not a problem for the same time in previous and next years. I only found it as I have a continuous sequence of date-times that cover that time period, the problem is not created by traversing that time with seq.POSIXt. I usually use Windows XP, below I also give results on Linux (release "2.4.21-37.ELsmp"). On that machine the times are incorrect in the other direction (in 2004, 2 AM is interpreted as 3 AM). My (Windows) system is set to automatically adjust for daylight summer time, and if I uncheck this and restart R the problem is "fixed". I don't know how I would do that on Linux, but it's a server anyway so I couldn't. ## R 2.2.0 ## Windows XP, SP2 ## System time is set to (GMT+10:00) Hobart - Tasmanian Summer Time (1 hour forward of GMT+10) Sys.getlocale() ## [1] "LC_COLLATE=English_Australia.1252;LC_CTYPE=English_Australia.1252;LC_MONETARY=English_Australia.1252;LC_NUMERIC=C;LC_TIME=English_Australia.1252" #### Try for 2004 (t1 <- ISOdatetime(2004, 10, 3, 1, 0, 0, tz = "GMT")) ##[1] "2004-10-03 01:00:00 GMT" (t2 <- ISOdatetime(2004, 10, 3, 2, 0, 0, tz = "GMT")) ##[1] "2004-10-03 01:00:00 GMT" ## no difference - why? t2 - t1 ## Time difference of 0 secs ## Try for 2005 (t1 <- ISOdatetime(2005, 10, 3, 1, 0, 0, tz = "GMT")) ##[1] "2005-10-03 01:00:00 GMT" (t2 <- ISOdatetime(2005, 10, 3, 2, 0, 0, tz = "GMT") ) ##[1] "2005-10-03 02:00:00 GMT" ## 1 hour difference - as expected t2 - t1 ## Time difference of 1 hours #### #### LINUX #### ## R 2.2.0 ## Linux (release "2.4.21-37.ELsmp" ## System time is set to (EST) - summer time (I don't know how to find more about this) Sys.getlocale() ## [1] "LC_CTYPE=en_AU.UTF-8;LC_NUMERIC=C;LC_TIME=en_AU.UTF-8;LC_COLLATE=en_AU.UTF-8;LC_MONETARY=en_AU.UTF-8;LC_MESSAGES=en_AU.UTF-8;LC_PAPER=C;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=C;LC_IDENTIFICATION=C" #### Try for 2004 (t1 <- ISOdatetime(2004, 10, 3, 1, 0, 0, tz = "GMT")) ## [1] "2004-10-03 01:00:00 GMT" (t2 <- ISOdatetime(2004, 10, 3, 2, 0, 0, tz = "GMT")) ##[1] "2004-10-03 03:00:00 GMT" ## difference of 2 hours - why? t2 - t1 ## Time difference of 2 hours ## Try for 2005 (t1 <- ISOdatetime(2005, 10, 3, 1, 0, 0, tz = "GMT")) ##[1] "2005-10-03 01:00:00 GMT" (t2 <- ISOdatetime(2005, 10, 3, 2, 0, 0, tz = "GMT") ) ##[1] "2005-10-03 02:00:00 GMT" ## one hour difference as expected t2 - t1 ## Time difference of 1 hours ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
