unknown timezone name in R strptime/as.POSIXct

Question

Where can I find a list of all legal time names for R function as.POSIXct?

as.POSIXct("1970-01-01",tz="CST") generates a warning that "CST" (Central Standard Time) is unknown.

Answer 1

Timezone stuff can drive you NUTS!!

Being located in Germany, this is what I used to do to set my tz:

> options(tz="Europe/Berlin") 

Doing so, I always wondered why R would throw "unknown timezone" warnings:

> t <- "2011-11-08 09:42:00" > as.POSIXct(t, tz=getOption("tz")) [1] "2011-11-08 09:42:00 CET" Warning messages: 1: In strptime(xx, f <- "%Y-%m-%d %H:%M:%OS", tz = tz) :   unknown timezone 'MET-1MST' 2: In as.POSIXct.POSIXlt(x) : unknown timezone 'MET-1MST' 3: In strptime(x, f, tz = tz) : unknown timezone 'MET-1MST' 4: In as.POSIXct.POSIXlt(as.POSIXlt(x, tz, ...), tz, ...) :   unknown timezone 'MET-1MST' 5: In as.POSIXlt.POSIXct(x, tz) : unknown timezone 'MET-1MST' 

Someday I found out that setting tz via options() was not enough as the environment variable TZ is not affected and hence all the the trouble:

> Sys.getenv("TZ") [1] "MET-1MST" 

Changing this should do away with the nasty warnings:

> Sys.setenv(TZ="Europe/Berlin") > Sys.getenv("TZ") [1] "Europe/Berlin" > as.POSIXct(t, tz=getOption("tz")) [1] "2011-11-08 09:42:00 CET"