diff --git a/Data/Time/LocalTime/TimeZone/Series.hs b/Data/Time/LocalTime/TimeZone/Series.hs
--- a/Data/Time/LocalTime/TimeZone/Series.hs
+++ b/Data/Time/LocalTime/TimeZone/Series.hs
@@ -34,10 +34,12 @@
 import Data.Maybe (listToMaybe, fromMaybe)
 import Data.Typeable (Typeable)
 import Control.Arrow (first)
+import Control.DeepSeq (NFData(..))
 
--- Conditional import, depending on whether time library is pre-1.6 or
--- post-1.6, controlled by cabal flag:
-import Data.Time.LocalTime.TimeZone.Internal.MapBuiltTime (mapBuiltTime)
+-- Conditional import, depending on the version of the time library,
+-- controlled by cabal flag:
+import Data.Time.LocalTime.TimeZone.Internal.TimeVersion (mapBuiltTime,
+  mapFormatCharacter)
 
 -- $abouttzs
 -- A @TimeZoneSeries@ describes a timezone with a set of 'TimeZone'
@@ -80,6 +82,9 @@
 instance Read TimeZoneSeries where
     readsPrec n = map (first $ flip TimeZoneSeries []) . readsPrec n
 
+instance NFData TimeZoneSeries where
+  rnf tzs = rnf (tzsTimeZone tzs, tzsTransitions tzs)
+
 instance ParseTime TimeZoneSeries where
   buildTime locale = mapBuiltTime (flip TimeZoneSeries []) . buildTime locale
 
@@ -93,7 +98,7 @@
 
 instance FormatTime TimeZoneSeries where
   formatCharacter = 
-    fmap (\f locale mpado -> f locale mpado . latestNonSummer) .
+    fmap (mapFormatCharacter latestNonSummer) .
     formatCharacter
 
 -- | Given a timezone represented by a @TimeZoneSeries@, and a @UTCTime@,
@@ -175,7 +180,7 @@
 
 instance FormatTime ZoneSeriesTime where
   formatCharacter =
-    fmap (\f locale mpado -> f locale mpado . zoneSeriesTimeToZonedTime) .
+    fmap (mapFormatCharacter zoneSeriesTimeToZonedTime) .
     formatCharacter
 
 -- | The @ZonedTime@ of a @ZoneSeriesTime@.
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -43,7 +43,7 @@
 packages for more information about reading and creating Olson
 timezone files.
 
-Copyright (c) 2010-2015 Yitzchak Gale. All rights reserved.
+Copyright (c) 2010-2016 Yitzchak Gale. All rights reserved.
 
 For licensing information, see the BSD3-style license in the file
 LICENSE that was originally distributed by the author together with
diff --git a/time_1_6_and_1_7/Data/Time/LocalTime/TimeZone/Internal/TimeVersion.hs b/time_1_6_and_1_7/Data/Time/LocalTime/TimeZone/Internal/TimeVersion.hs
new file mode 100644
--- /dev/null
+++ b/time_1_6_and_1_7/Data/Time/LocalTime/TimeZone/Internal/TimeVersion.hs
@@ -0,0 +1,16 @@
+-- | Functions that depend on the version of the @time@ library
+
+module Data.Time.LocalTime.TimeZone.Internal.TimeVersion
+(
+   mapBuiltTime
+ , mapFormatCharacter
+)
+where
+
+-- | Map over 'Maybe' for 'buildTime' for post-1.6 time library.
+mapBuiltTime :: Functor f => (a -> b) -> f a -> f b
+mapBuiltTime = fmap
+
+-- | Map for 'formatCharacter' for pre-1.8 time library.
+mapFormatCharacter :: (a -> b) -> (c -> d -> b -> z) -> c -> d -> a -> z
+mapFormatCharacter f g locale mpado = g locale mpado . f
diff --git a/time_post_1_6/Data/Time/LocalTime/TimeZone/Internal/MapBuiltTime.hs b/time_post_1_6/Data/Time/LocalTime/TimeZone/Internal/MapBuiltTime.hs
deleted file mode 100644
--- a/time_post_1_6/Data/Time/LocalTime/TimeZone/Internal/MapBuiltTime.hs
+++ /dev/null
@@ -1,11 +0,0 @@
--- | Specify the mapping function for 'buildTime'.
-
-module Data.Time.LocalTime.TimeZone.Internal.MapBuiltTime
-(
-  mapBuiltTime
-)
-where
-
--- | Map over 'Maybe' for 'buildTime' for post-1.6 time library.
-mapBuiltTime :: Functor f => (a -> b) -> f a -> f b
-mapBuiltTime = fmap
diff --git a/time_post_1_8/Data/Time/LocalTime/TimeZone/Internal/TimeVersion.hs b/time_post_1_8/Data/Time/LocalTime/TimeZone/Internal/TimeVersion.hs
new file mode 100644
--- /dev/null
+++ b/time_post_1_8/Data/Time/LocalTime/TimeZone/Internal/TimeVersion.hs
@@ -0,0 +1,17 @@
+-- | Functions that depend on the version of the @time@ library
+
+module Data.Time.LocalTime.TimeZone.Internal.TimeVersion
+(
+   mapBuiltTime
+ , mapFormatCharacter
+)
+where
+
+-- | Map over 'Maybe' for 'buildTime' for post-1.6 time library.
+mapBuiltTime :: Functor f => (a -> b) -> f a -> f b
+mapBuiltTime = fmap
+
+-- | Map for 'formatCharacter' for post-1.8 time library.
+mapFormatCharacter ::
+  (a -> b) -> (c -> d -> e -> b -> z) -> c -> d -> e -> a -> z
+mapFormatCharacter f g locale mpado mwidth = g locale mpado mwidth . f
diff --git a/time_pre_1_6/Data/Time/LocalTime/TimeZone/Internal/MapBuiltTime.hs b/time_pre_1_6/Data/Time/LocalTime/TimeZone/Internal/MapBuiltTime.hs
deleted file mode 100644
--- a/time_pre_1_6/Data/Time/LocalTime/TimeZone/Internal/MapBuiltTime.hs
+++ /dev/null
@@ -1,11 +0,0 @@
--- | Specify the mapping function for 'buildTime'.
-
-module Data.Time.LocalTime.TimeZone.Internal.MapBuiltTime
-(
-  mapBuiltTime
-)
-where
-
--- | No mapping needed for 'buildTime' for pre-1.6 time library.
-mapBuiltTime :: a -> a
-mapBuiltTime = id
diff --git a/time_pre_1_6/Data/Time/LocalTime/TimeZone/Internal/TimeVersion.hs b/time_pre_1_6/Data/Time/LocalTime/TimeZone/Internal/TimeVersion.hs
new file mode 100644
--- /dev/null
+++ b/time_pre_1_6/Data/Time/LocalTime/TimeZone/Internal/TimeVersion.hs
@@ -0,0 +1,16 @@
+-- | Functions that depend on the version of the @time@ library
+
+module Data.Time.LocalTime.TimeZone.Internal.TimeVersion
+(
+   mapBuiltTime
+ , mapFormatCharacter
+)
+where
+
+-- | No mapping needed for 'buildTime' for pre-1.6 time library.
+mapBuiltTime :: a -> a
+mapBuiltTime = id
+
+-- | Map for 'formatCharacter' for pre-1.8 time library.
+mapFormatCharacter :: (a -> b) -> (c -> d -> b -> z) -> c -> d -> a -> z
+mapFormatCharacter f g locale mpado = g locale mpado . f
diff --git a/timezone-series.cabal b/timezone-series.cabal
--- a/timezone-series.cabal
+++ b/timezone-series.cabal
@@ -1,5 +1,5 @@
 Name:                timezone-series
-Version:             0.1.6.1
+Version:             0.1.8
 Synopsis:            Enhanced timezone handling for Data.Time
 Description:         This package endows Data.Time, from the time
                      package, with several data types and functions
@@ -19,6 +19,8 @@
 Build-type:          Simple
 Extra-source-files:  README.md
 Cabal-version:       >=1.10
+Tested-with:         GHC > 7.4 && < 8.1
+
 Source-repository HEAD
   type:              git
   location:          https://github.com/ygale/timezone-series.git
@@ -27,18 +29,29 @@
   Description:       Use version < 1.6 of the time library
   Default:           False
 
+Flag time_1_6_and_1_7
+  Description:       Use version >= 1.6 and < 1.8 of the time library
+  Default:           False
+
 Library
   Default-language:    Haskell2010
   Hs-source-dirs:      .
   if flag(time_pre_1_6)
     Hs-source-dirs:    time_pre_1_6
   else
-    Hs-source-dirs:    time_post_1_6
+    if flag(time_1_6_and_1_7)
+      Hs-source-dirs:  time_1_6_and_1_7
+    else
+      Hs-source-dirs:  time_post_1_8
   Exposed-modules:     Data.Time.LocalTime.TimeZone.Series
-  Other-modules:       Data.Time.LocalTime.TimeZone.Internal.MapBuiltTime
+  Other-modules:       Data.Time.LocalTime.TimeZone.Internal.TimeVersion
   Default-extensions:  DeriveDataTypeable
   Build-depends:       base >= 4.4 && < 5
+                     , deepseq
   if flag(time_pre_1_6)
     Build-depends:     time >= 1.1.4 && < 1.6
   else
-    Build-depends:     time >= 1.6 && < 1.7
+    if flag(time_1_6_and_1_7)
+      Build-depends:   time >= 1.6 && < 1.8
+    else
+      Build-depends:   time >= 1.8 && < 1.9