Code to parse Github dates out of it's API using Aeson

GithubDate.hs

{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE OverloadedStrings #-}
module Main where

import Data.Aeson       (FromJSON(..), Value(..), Result(..))
import Data.Aeson.Types (parse)
import Data.Time.Clock  (UTCTime)
import Data.Time.Format (FormatTime, parseTime)
import Data.Typeable    (Typeable)
import Data.Text        (unpack)
import System.Locale    (defaultTimeLocale)

newtype GithubTime
  = GithubTime {
    fromGithubTime :: UTCTime
  }
  deriving (Eq, Ord, Read, Show, Typeable, FormatTime)


-- Date Format:
-- "2011/08/10 11:30:58 -0700"

instance FromJSON GithubTime where
  parseJSON (String t) =
    case parseTime defaultTimeLocale "%Y/%m/%d %T %z" (unpack t) of
      Just d -> return (GithubTime d)
      _ -> fail "Could not parse github date"


main :: IO ()
main = 
    print $ result
  where
    json   = String "2011/08/10 11:30:58 -0700"
    result = (parse parseJSON json :: Result GithubTime)