diff --git a/chronos.cabal b/chronos.cabal
--- a/chronos.cabal
+++ b/chronos.cabal
@@ -1,5 +1,5 @@
 name: chronos
-version: 1.0.2
+version: 1.0.3
 synopsis: A performant time library
 description:
   Performance-oriented time library for haskell. The main differences
@@ -43,16 +43,17 @@
   other-modules:
       Chronos.Internal.CTimespec
   build-depends:
-      base >= 4.8 && < 5
-    , vector >= 0.11 && < 0.13
-    , text >= 1.2 && < 1.3
-    , bytestring >= 0.10 && < 0.11
+      base >= 4.9 && < 5
+    , aeson >= 1.1 && < 1.4
     , attoparsec >= 0.13 && < 0.14
-    , aeson >= 1.1 && < 1.3
+    , bytestring >= 0.10 && < 0.11
+    , clock >= 0.7 && < 0.8
     , hashable >= 1.2 && < 1.3
     , primitive >= 0.6 && < 0.7
+    , semigroups >= 0.16 && < 0.19
+    , text >= 1.2 && < 1.3
     , torsor >= 0.1 && < 0.2
-    , clock >= 0.7 && < 0.8
+    , vector >= 0.11 && < 0.13
   default-language:    Haskell2010
   c-sources:           src/cbits/hs-time.c
 
diff --git a/src/Chronos.hs b/src/Chronos.hs
--- a/src/Chronos.hs
+++ b/src/Chronos.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE MagicHash #-}
@@ -6,6 +7,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeInType #-}
 {-# LANGUAGE UnboxedTuples #-}
 
 {-# OPTIONS_GHC -Wall #-}
@@ -198,7 +200,6 @@
 
 import Data.Text (Text)
 import Data.Vector (Vector)
-import Data.Monoid
 import Data.Attoparsec.Text (Parser)
 import Control.Monad
 import Data.Foldable
@@ -216,26 +217,31 @@
 import Foreign.Storable
 import Data.Hashable (Hashable)
 import Control.Exception (evaluate)
-import qualified System.Clock as CLK
 import qualified Data.Aeson as AE
 import qualified Data.Aeson.Encoding as AEE
 import qualified Data.Aeson.Types as AET
-import qualified Data.Text as Text
-import qualified Data.Text.Read as Text
-import qualified Data.Attoparsec.Text as AT
 import qualified Data.Attoparsec.ByteString.Char8 as AB
-import qualified Data.Vector as Vector
-import qualified Data.Text.Lazy.Builder as TB
-import qualified Data.Text.Lazy.Builder.Int as TB
+import qualified Data.Attoparsec.Text as AT
 import qualified Data.ByteString.Builder as BB
 import qualified Data.ByteString.Char8 as BC
-import qualified Data.Text.Lazy as LT
 import qualified Data.ByteString.Lazy as LB
-import qualified Data.Vector.Unboxed as UVector
+import qualified Data.Semigroup as SG
+import qualified Data.Text as Text
+import qualified Data.Text.Lazy as LT
+import qualified Data.Text.Lazy.Builder as TB
+import qualified Data.Text.Lazy.Builder.Int as TB
+import qualified Data.Text.Read as Text
+import qualified Data.Vector as Vector
 import qualified Data.Vector.Generic as GVector
-import qualified Data.Vector.Primitive as PVector
 import qualified Data.Vector.Generic.Mutable as MGVector
+import qualified Data.Vector.Primitive as PVector
+import qualified Data.Vector.Unboxed as UVector
+import qualified System.Clock as CLK
 
+#if !MIN_VERSION_base(4,11,0)
+import Data.Semigroup (Semigroup, (<>))
+#endif
+
 second :: Timespan
 second = Timespan 1000000000
 
@@ -1784,7 +1790,7 @@
     else error "Enum.succ{Month}: tried to take succ of December"
   pred (Month x) = if x > 0
     then Month (x - 1)
-    else error "Enum.pred{Month}: tried to take succ of January"
+    else error "Enum.pred{Month}: tried to take pred of January"
   enumFrom x = enumFromTo x (Month 11)
 
 instance Bounded Month where
@@ -1814,9 +1820,12 @@
 newtype Timespan = Timespan { getTimespan :: Int64 }
   deriving (Show,Read,Eq,Ord,ToJSON,FromJSON,Additive)
 
+instance Semigroup Timespan where
+  (Timespan a) <> (Timespan b) = Timespan (a + b)
+
 instance Monoid Timespan where
   mempty = Timespan 0
-  mappend (Timespan a) (Timespan b) = Timespan (a + b)
+  mappend = (SG.<>)
 
 instance Torsor Time Timespan where
   add (Timespan ts) (Time t) = Time (t + ts)
@@ -2057,11 +2066,11 @@
 
 instance ToJSON Datetime where
   toJSON = AE.String . encode_YmdHMS SubsecondPrecisionAuto hyphen
-  toEncoding x = AEE.unsafeToEncoding (BB.char7 '"' <> builderUtf8_YmdHMS SubsecondPrecisionAuto hyphen x <> BB.char7 '"')
+  toEncoding x = AEE.unsafeToEncoding (BB.char7 '"' SG.<> builderUtf8_YmdHMS SubsecondPrecisionAuto hyphen x SG.<> BB.char7 '"')
 
 instance ToJSON Offset where
   toJSON = AE.String . encodeOffset OffsetFormatColonOn
-  toEncoding x = AEE.unsafeToEncoding (BB.char7 '"' <> builderOffsetUtf8 OffsetFormatColonOn x <> BB.char7 '"')
+  toEncoding x = AEE.unsafeToEncoding (BB.char7 '"' SG.<> builderOffsetUtf8 OffsetFormatColonOn x SG.<> BB.char7 '"')
 
 instance FromJSON Offset where
   parseJSON = AE.withText "Offset" aesonParserOffset
@@ -2069,7 +2078,7 @@
 instance ToJSONKey Offset where
   toJSONKey = AE.ToJSONKeyText
     (encodeOffset OffsetFormatColonOn)
-    (\x -> AEE.unsafeToEncoding (BB.char7 '"' <> builderOffsetUtf8 OffsetFormatColonOn x <> BB.char7 '"'))
+    (\x -> AEE.unsafeToEncoding (BB.char7 '"' SG.<> builderOffsetUtf8 OffsetFormatColonOn x SG.<> BB.char7 '"'))
 
 instance FromJSONKey Offset where
   fromJSONKey = AE.FromJSONKeyTextParser aesonParserOffset