time at a specified timezone, disregard daylights savings time
I have time series data obtained from a data logger that was set to one time zone without daylights 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?
You can use tz="Etc/GMT+12" :
as.POSIXct(ts_str, format="%d/%m/%Y %H:%M", tz="Etc/GMT+12")
[1] "2008-09-28 01:00:00 GMT+12" "2008-09-28 02:00:00 GMT+12"
[3] "2008-09-28 03:00:00 GMT+12"
For a full list of available timezones use,
dir(file.path(R.home("share"),"zoneinfo"), recursive=TRUE)
There are a couple of of .tab files in there which aren't timezones but hold some information, but my regex-fu isn't good enough to be able to exclude them with the pattern argument to dir .
如果只是将12 * 60 * 60添加到UTC派生矢量，您将拥有本地“标准”时间。
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