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I have time series data obtained from a data logger that was set to one time zone without daylight savings ( NZST or UTC+12:00), and the data spans a few years. Data loggers don't consider DST changes, and are synchronized to local time with/without DST (depending who deployed it). However, when I get the data into R, I'm unable to properly use as.POSIXct to ignore DST. I'm using R 2.14.0 on a Windows computer with these settings: > Sys.timezone() [1] "NZDT" > Sys.getlocale("LC_TIME") [1] "English_New Zealand.1252" Here are three timestamps across the spring DST change, each are spaced 1 hour apart: > ts_str <- c("28/09/2008 01:00", "28/09/2008 02:00", "28/09/2008 03:00") > as.POSIXct(ts_str, format="%d/%m/%Y %H:%M", tz="") [1] "2008-09-28 01:00:00 NZST" NA [3] "2008-09-28 03:00:00 NZDT" > as.POSIXct(ts_str, format="%d/%m/%Y %H:%M", tz="UTC") [1] "2008-09-28 01:00:00 UTC" "2008-09-28 02:00:00 UTC" [3] "2008-09-28 03:00:00 UTC" As you can see, the clocks jumped forward at 1:59 to 3:00, so 2:00 is invalid, thus NA. Furthermore, I can use tz="UTC" to get it to ignore DST changes. However, I'd rather keep the correct time zone since I have other data series recorded with DST (NZDT or UTC+13:00) that I'd like to blend in (via merge ) for my analysis. How do I configure the tz parameter on a MS Windows computer? I've tried many things, such as "NZST", "New Zealand Standard Time", "UTC+12:00", "+1200", etc., but no luck. Or do I modify some other setting?

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