Perhaps because the timezone is specified as a character string and not a date-time object complete with timezone.
>From the help filr for as.POSIXct.numeric: "origin: a date-time object, or something which can be coerced by as.POSIXct(tz="GMT") to such an object." Note the coercion. Bill Venables. -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Galen Moore Sent: Tuesday, 31 May 2011 12:20 PM To: r-help@r-project.org Subject: [R] DateTime Math in R - POSIXct Greetings - I'm battling POSIXct, as per the code below. My input is actually an XL file, but the weird results below correctly model what I am seeing in my program. Before I punt and use lubridate or timeDate, could anyone please help me understand why POSIXct forces my variable back to GMT? I suspect that I'm not properly coding the tzone value, but it does not throw an error as-is. > tstamp <- "2011-05-22 11:45:00 MDT" > mode(tstamp) [1] "character" > > dateP <- as.POSIXct(tstamp, origin="1970-01-01", tzone="MDT") > mode(dateP) [1] "numeric" > dateP [1] "2011-05-22 11:45:00 MDT" > > dateN <- as.numeric(dateP) > dateN [1] 1306086300 > > dateP2 <- as.POSIXct(dateN, origin="1970-01-01", tzone="MDT") > dateP2 [1] "2011-05-22 18:45:00 MDT" Many thanks. Galen Moore [[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. ______________________________________________ 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.
