Re: [Haskell-cafe] timezone-series and timezone-olson

27 Mar 2011

      Hi Yitz,
Thanks for answering so quickly.

On Sun, 27 Mar 2011 14:16:50 +0200
Yitzchak Gale  wrote:
...
Hi Manfred,
...
runhaskell caltest.hs
"  03/27/11\n"
...
I am copying this response to the Haskell Cafe mailing list.
Manfred Lotz wrote:
...
...I'm trying to figure out how to use your
packages to get the time in a different timezone.
Do you have an example how to do that? What I want for example is to
provide the timezone preferably like this: US/Eastern, and get the
time information like for example this:
US/Eastern        DST  EDT   2011.03.27 05:20:52
The pieces I like to get are: Summertime indicator, TZ abbrev and
the date resp. time in that timezone.
...
...
Assuming you have the timezone file that you need - let's say it
is in the directory /usr/share/zoneinfo as typical for Linux and
Mac - here is how to code it:
do
  ...
  tzs <- getTimeZoneSeriesFromOlsonFile
"/usr/share/zoneinfo/America/New_York" let usEastern =
utcToLocalTime' tzs utc
Then, to format the time as you require, use the formatTime function
from the time package.
I tried it like this:

<------------------------------snip--------------------------------->

module Main where

import System.Environment
import System.Exit
import System.Locale
import Data.Time
import Data.Time.Clock
import Data.Time.LocalTime
import Data.Time.LocalTime.TimeZone.Olson 
import Data.Time.LocalTime.TimeZone.Series

path = "/usr/share/zoneinfo/"

showTime t = fmap (formatTime defaultTimeLocale "%Z %z %D%n") t

getTime :: [Char] -> IO LocalTime
getTime tz = do
  tzs <- getTimeZoneSeriesFromOlsonFile (path ++ tz)
  utcnow <- getCurrentTime
  let tzo = utcToLocalTime' tzs utcnow in return tzo

main = let t = getTime "US/Eastern"
       in showTime 
<------------------------------snap--------------------------------->

Don't know if this is the proper way to do. In the output I do not get
the timezone information:
...
runhaskell caltest.hs
"  03/27/11\n"
Don't know what I'm doing wrong.	

-- 
Manfred