beakerchu:
Hurrah, I am now calling the C function tzset() from my Haskell code via FFI, and I'm getting the results I want.
$ cat hsc2now.hs {-# LANGUAGE ForeignFunctionInterface #-} import Data.Time import Data.Time.LocalTime import System.Environment import System.Posix.Env foreign import ccall "time.h tzset" tzset :: IO () outTime utc tzName = do putEnv ("TZ=" ++ tzName) tzset tz <- getTimeZone utc putStrLn (tzName ++ "\t" ++ show (utcToLocalTime tz utc)) main = do utc <- getCurrentTime mapM_ (outTime utc) =<< getArgs $ ghc --make hsc2now.hs -o hsc2now [1 of 1] Compiling Main ( hsc2now.hs, hsc2now.o ) Linking hsc2now ... $ ./hsc2now Europe/Moscow Europe/Paris Europe/London Europe/Moscow 2008-02-17 22:06:44.770153 Europe/Paris 2008-02-17 20:06:44.770153 Europe/London 2008-02-17 19:06:44.770153
Thank you everyone for your help :-)
Perhaps we should get a binding to tzset in the unix library?