diff --git a/exec/period.hs b/exec/period.hs
--- a/exec/period.hs
+++ b/exec/period.hs
@@ -1,10 +1,14 @@
 {-# LANGUAGE OverloadedStrings #-}
+
 module Main where
 
-import Text.Period
-import Options.Applicative
-import qualified Data.Text as T
-import qualified Data.Text.IO as T
+import           Data.Monoid
+import qualified Data.Text           as T
+import qualified Data.Text.IO        as T
+import           Options.Applicative
+import           Text.Period
+
+import Prelude
 
 main :: IO ()
 main = execParser (info (helper <*> optParser) $ progDesc "period") >>= runCommand
diff --git a/period.cabal b/period.cabal
--- a/period.cabal
+++ b/period.cabal
@@ -1,5 +1,5 @@
 name:                period
-version:             0.1.0.0
+version:             0.1.0.1
 synopsis:            Parse and format date periods, collapse and expand their text representations.
 -- description:         
 homepage:            https://github.com/w3rs/period
@@ -16,8 +16,8 @@
 library
   exposed-modules:     Text.Period
   build-depends:
-                base >=4.6 && < 5,
-                time >=1.4,
+                base >=4.6 && < 4.9,
+                time >=1.5,
                 text >= 1.2,
                 text-show >= 2,
                 parsec >= 3.1
diff --git a/src/Text/Period.hs b/src/Text/Period.hs
--- a/src/Text/Period.hs
+++ b/src/Text/Period.hs
@@ -1,36 +1,38 @@
-{-# LANGUAGE LambdaCase   #-}
-{-# LANGUAGE MultiWayIf   #-}
-{-# LANGUAGE ViewPatterns #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ConstraintKinds       #-}
+{-# LANGUAGE FlexibleContexts      #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE MultiWayIf            #-}
+{-# LANGUAGE OverloadedStrings     #-}
+{-# LANGUAGE ScopedTypeVariables   #-}
 
 module Text.Period
  ( Period, PeriodFmt(..), parsePeriod, parsePeriodMay, parsePeriodEither
  , formatPeriod, collapsePeriod
  )where
 
+import           Control.Applicative hiding ((<|>))
 import           Control.Arrow
 import           Control.Monad
 import           Data.Char
-import           Data.Monoid ((<>))
-import qualified Data.Text as T
+import           Data.Monoid         ((<>))
+import qualified Data.Text           as T
 import           Data.Time
-import           TextShow (showt)
 
-import           Text.Parsec.Char
-import           Text.Parsec.Combinator
-import           Text.Parsec.Prim
-import           Text.Parsec.Text
+import Prelude
+import TextShow (showt)
 
+import Text.Parsec.Char
+import Text.Parsec.Combinator
+import Text.Parsec.Prim
+import Text.Parsec.Text
 
+
 type Period = (Day, Day)
 
 data PeriodFmt = PeriodFmt
   { perFieldSep :: T.Text -- ^ Separator between year, month and day
-  , perDateSep :: T.Text -- ^ Separator between dates in the range, e.g. comma
-                         -- in @yyyy-mm-dd,yyyy-mm-dd@
+  , perDateSep  :: T.Text -- ^ Separator between dates in the range, e.g. comma
+                          -- in @yyyy-mm-dd,yyyy-mm-dd@
   }
 
 data ParseState