diff --git a/include/thyme.h b/include/thyme.h
--- a/include/thyme.h
+++ b/include/thyme.h
@@ -1,5 +1,5 @@
 #define INSTANCES_USUAL     Eq, Ord, Data, Typeable, Generic
-#define INSTANCES_NEWTYPE   INSTANCES_USUAL, Enum, Ix, NFData
+#define INSTANCES_NEWTYPE   INSTANCES_USUAL, Enum, Ix, NFData, MVector VUM.MVector, Vector VU.Vector, VUM.Unbox
 #define INSTANCES_MICRO     INSTANCES_NEWTYPE, Bounded, Random, Arbitrary, CoArbitrary
 #define LensP Lens'
 #define LENS(S,F,A) {-# INLINE _/**/F #-}; _/**/F :: LensP S A; _/**/F = lens F $ \ S {..} F/**/_ -> S {F = F/**/_, ..}
diff --git a/src/Data/Thyme/Calendar/Internal.hs b/src/Data/Thyme/Calendar/Internal.hs
--- a/src/Data/Thyme/Calendar/Internal.hs
+++ b/src/Data/Thyme/Calendar/Internal.hs
@@ -25,8 +25,10 @@
 import Data.Int
 import Data.Ix
 import Data.Thyme.Format.Internal
-import Data.Vector.Unboxed (Vector)
-import qualified Data.Vector.Unboxed as V
+import Data.Vector.Generic (Vector)
+import Data.Vector.Generic.Mutable (MVector)
+import qualified Data.Vector.Unboxed as VU
+import qualified Data.Vector.Unboxed.Mutable as VUM
 import GHC.Generics (Generic)
 import System.Random
 import Test.QuickCheck hiding ((.&.))
@@ -44,9 +46,9 @@
 instance AffineSpace Day where
     type Diff Day = Days
     {-# INLINE (.-.) #-}
-    ModifiedJulianDay a .-. ModifiedJulianDay b = a - b
+    (.-.) = \ (ModifiedJulianDay a) (ModifiedJulianDay b) -> a - b
     {-# INLINE (.+^) #-}
-    ModifiedJulianDay a .+^ d = ModifiedJulianDay (a + d)
+    (.+^) = \ (ModifiedJulianDay a) d -> ModifiedJulianDay (a + d)
 
 {-# INLINE modifiedJulianDay #-}
 modifiedJulianDay :: Iso' Day Int
@@ -146,28 +148,28 @@
 
 {-# NOINLINE monthLengths #-}
 {-# NOINLINE monthLengthsLeap #-}
-monthLengths, monthLengthsLeap :: Vector Days
-monthLengths     = V.fromList [31,28,31,30,31,30,31,31,30,31,30,31]
-monthLengthsLeap = V.fromList [31,29,31,30,31,30,31,31,30,31,30,31]
+monthLengths, monthLengthsLeap :: VU.Vector Days
+monthLengths     = VU.fromList [31,28,31,30,31,30,31,31,30,31,30,31]
+monthLengthsLeap = VU.fromList [31,29,31,30,31,30,31,31,30,31,30,31]
                             -- J  F  M  A  M  J  J  A  S  O  N  D
 
 {-# ANN monthDays "HLint: ignore Use fromMaybe" #-}
 {-# NOINLINE monthDays #-}
-monthDays :: Vector ({-Month-}Int8, {-DayOfMonth-}Int8)
-monthDays = V.generate 365 go where
-    dom01 = V.prescanl' (+) 0 monthLengths
+monthDays :: VU.Vector ({-Month-}Int8, {-DayOfMonth-}Int8)
+monthDays = VU.generate 365 go where
+    dom01 = VU.prescanl' (+) 0 monthLengths
     go yd = (fromIntegral m, fromIntegral d) where
-        m = maybe 12 id $ V.findIndex (yd <) dom01
-        d = succ yd - V.unsafeIndex dom01 (pred m)
+        m = maybe 12 id $ VU.findIndex (yd <) dom01
+        d = succ yd - VU.unsafeIndex dom01 (pred m)
 
 {-# ANN monthDaysLeap "HLint: ignore Use fromMaybe" #-}
 {-# NOINLINE monthDaysLeap #-}
-monthDaysLeap :: Vector ({-Month-}Int8, {-DayOfMonth-}Int8)
-monthDaysLeap = V.generate 366 go where
-    dom01 = V.prescanl' (+) 0 monthLengthsLeap
+monthDaysLeap :: VU.Vector ({-Month-}Int8, {-DayOfMonth-}Int8)
+monthDaysLeap = VU.generate 366 go where
+    dom01 = VU.prescanl' (+) 0 monthLengthsLeap
     go yd = (fromIntegral m, fromIntegral d) where
-        m = maybe 12 id $ V.findIndex (yd <) dom01
-        d = succ yd - V.unsafeIndex dom01 (pred m)
+        m = maybe 12 id $ VU.findIndex (yd <) dom01
+        d = succ yd - VU.unsafeIndex dom01 (pred m)
 
 -- | No good home for this within the current hierarchy. This will do.
 {-# INLINEABLE randomIsoR #-}
@@ -211,13 +213,13 @@
     {-# INLINE fromOrdinal #-}
     fromOrdinal :: DayOfYear -> MonthDay
     fromOrdinal (max 0 . min lastDay . pred -> i) = MonthDay m d where
-        (fromIntegral -> m, fromIntegral -> d) = V.unsafeIndex table i
+        (fromIntegral -> m, fromIntegral -> d) = VU.unsafeIndex table i
 
     {-# INLINE toOrdinal #-}
     toOrdinal :: MonthDay -> DayOfYear
     toOrdinal (MonthDay month day) = div (367 * m - 362) 12 + k + d where
         m = max 1 . min 12 $ month
-        l = V.unsafeIndex lengths (pred m)
+        l = VU.unsafeIndex lengths (pred m)
         d = max 1 . min l $ day
         k = if m <= 2 then 0 else ok
 
@@ -228,7 +230,7 @@
 
 {-# INLINEABLE monthLength #-}
 monthLength :: Bool -> Month -> Days
-monthLength leap = V.unsafeIndex ls . max 0 . min 11 . pred where
+monthLength leap = VU.unsafeIndex ls . max 0 . min 11 . pred where
     ls = if leap then monthLengthsLeap else monthLengths
 
 ------------------------------------------------------------------------
diff --git a/src/Data/Thyme/Calendar/WeekdayOfMonth.hs b/src/Data/Thyme/Calendar/WeekdayOfMonth.hs
--- a/src/Data/Thyme/Calendar/WeekdayOfMonth.hs
+++ b/src/Data/Thyme/Calendar/WeekdayOfMonth.hs
@@ -5,7 +5,10 @@
 {-# LANGUAGE ViewPatterns #-}
 #include "thyme.h"
 
-module Data.Thyme.Calendar.WeekdayOfMonth where
+module Data.Thyme.Calendar.WeekdayOfMonth
+    ( Year, Month, DayOfWeek
+    , module Data.Thyme.Calendar.WeekdayOfMonth
+    ) where
 
 import Prelude
 import Control.Applicative
diff --git a/src/Data/Thyme/Clock/Internal.hs b/src/Data/Thyme/Clock/Internal.hs
--- a/src/Data/Thyme/Clock/Internal.hs
+++ b/src/Data/Thyme/Clock/Internal.hs
@@ -23,6 +23,10 @@
 import Data.Ix
 import Data.Thyme.Internal.Micro
 import Data.Thyme.Calendar.Internal
+import Data.Vector.Generic (Vector)
+import Data.Vector.Generic.Mutable (MVector)
+import qualified Data.Vector.Unboxed as VU
+import qualified Data.Vector.Unboxed.Mutable as VUM
 import Data.VectorSpace
 import GHC.Generics (Generic)
 import System.Random
@@ -69,9 +73,11 @@
 ------------------------------------------------------------------------
 -- not for public consumption
 
+{-# INLINE fromSecondsRealFrac #-}
 fromSecondsRealFrac :: (RealFrac n, TimeDiff t) => n -> n -> t
 fromSecondsRealFrac _ = review microseconds . round . (*) 1000000
 
+{-# INLINE fromSecondsIntegral #-}
 fromSecondsIntegral :: (Integral n, TimeDiff t) => n -> n -> t
 fromSecondsIntegral _ = review microseconds . (*) 1000000 . fromIntegral
 
@@ -113,16 +119,16 @@
 instance VectorSpace DiffTime where
     type Scalar DiffTime = Rational
     {-# INLINE (*^) #-}
-    s *^ DiffTime t = DiffTime (s *^ t)
+    (*^) = \ s (DiffTime t) -> DiffTime (s *^ t)
 
 instance HasBasis DiffTime where
     type Basis DiffTime = ()
     {-# INLINE basisValue #-}
-    basisValue () = DiffTime (basisValue ())
+    basisValue = \ _ -> DiffTime (basisValue ())
     {-# INLINE decompose #-}
-    decompose (DiffTime a) = decompose a
+    decompose = \ (DiffTime a) -> decompose a
     {-# INLINE decompose' #-}
-    decompose' (DiffTime a) = decompose' a
+    decompose' = \ (DiffTime a) -> decompose' a
 
 instance TimeDiff DiffTime where
     {-# INLINE microseconds #-}
@@ -161,16 +167,16 @@
 instance VectorSpace NominalDiffTime where
     type Scalar NominalDiffTime = Rational
     {-# INLINE (*^) #-}
-    s *^ NominalDiffTime t = NominalDiffTime (s *^ t)
+    (*^) = \ s (NominalDiffTime t) -> NominalDiffTime (s *^ t)
 
 instance HasBasis NominalDiffTime where
     type Basis NominalDiffTime = ()
     {-# INLINE basisValue #-}
-    basisValue () = NominalDiffTime (basisValue ())
+    basisValue = \ _ -> NominalDiffTime (basisValue ())
     {-# INLINE decompose #-}
-    decompose (NominalDiffTime a) = decompose a
+    decompose = \ (NominalDiffTime a) -> decompose a
     {-# INLINE decompose' #-}
-    decompose' (NominalDiffTime a) = decompose' a
+    decompose' = \ (NominalDiffTime a) -> decompose' a
 
 instance TimeDiff NominalDiffTime where
     {-# INLINE microseconds #-}
@@ -245,9 +251,9 @@
 instance AffineSpace UTCTime where
     type Diff UTCTime = NominalDiffTime
     {-# INLINE (.-.) #-}
-    UTCRep a .-. UTCRep b = a ^-^ b
+    (.-.) = \ (UTCRep a) (UTCRep b) -> a ^-^ b
     {-# INLINE (.+^) #-}
-    UTCRep a .+^ d = UTCRep (a ^+^ d)
+    (.+^) = \ (UTCRep a) d -> UTCRep (a ^+^ d)
 
 -- | View 'UTCTime' as an 'UTCView', comprising a 'Day' along with
 -- a 'DiffTime' offset since midnight.
diff --git a/src/Data/Thyme/Clock/TAI.hs b/src/Data/Thyme/Clock/TAI.hs
--- a/src/Data/Thyme/Clock/TAI.hs
+++ b/src/Data/Thyme/Clock/TAI.hs
@@ -44,6 +44,10 @@
 import Data.Thyme.Clock.Internal
 import Data.Thyme.Format.Internal
 import Data.Thyme.LocalTime
+import Data.Vector.Generic (Vector)
+import Data.Vector.Generic.Mutable (MVector)
+import qualified Data.Vector.Unboxed as VU
+import qualified Data.Vector.Unboxed.Mutable as VUM
 import Data.VectorSpace
 import GHC.Generics (Generic)
 import System.Locale
@@ -65,9 +69,9 @@
 instance AffineSpace AbsoluteTime where
     type Diff AbsoluteTime = DiffTime
     {-# INLINE (.-.) #-}
-    AbsoluteTime a .-. AbsoluteTime b = a ^-^ b
+    (.-.) = \ (AbsoluteTime a) (AbsoluteTime b) -> a ^-^ b
     {-# INLINE (.+^) #-}
-    AbsoluteTime a .+^ d = AbsoluteTime (a ^+^ d)
+    (.+^) = \ (AbsoluteTime a) d -> AbsoluteTime (a ^+^ d)
 
 type LeapSecondTable = Either UTCTime AbsoluteTime -> DiffTime
 
diff --git a/src/Data/Thyme/Format/Aeson.hs b/src/Data/Thyme/Format/Aeson.hs
--- a/src/Data/Thyme/Format/Aeson.hs
+++ b/src/Data/Thyme/Format/Aeson.hs
@@ -24,7 +24,7 @@
 --              (c) 2011 MailRank, Inc.
 
 ------------------------------------------------------------------------
--- Copypasta from aeson-0.7.0.0:Data.Aeson.Types.Internal
+-- Copypasta from aeson-0.7.1.0:Data.Aeson.Types.Internal
 
 -- | A newtype wrapper for 'UTCTime' that uses the same non-standard
 -- serialization format as Microsoft .NET, whose @System.DateTime@
@@ -38,7 +38,7 @@
     } deriving (Eq, Ord, Read, Show, Typeable, FormatTime)
 
 ------------------------------------------------------------------------
--- Copypasta from aeson-0.7.0.0:Data.Aeson.Types.Instances
+-- Copypasta from aeson-0.7.1.0:Data.Aeson.Types.Instances
 
 instance ToJSON DotNetTime where
     toJSON (DotNetTime t) =
@@ -88,8 +88,9 @@
     parseJSON v = typeMismatch "ZonedTime" v
 
 instance ToJSON UTCTime where
-    toJSON t = String (pack (take 23 str ++ "Z"))
-      where str = formatTime defaultTimeLocale "%FT%T.%q" t
+    toJSON t = String $ pack $ formatTime defaultTimeLocale format t
+      where
+        format = "%FT%T." ++ formatMillis t ++ "Z"
     {-# INLINE toJSON #-}
 
 instance FromJSON UTCTime where
diff --git a/src/Data/Thyme/Internal/Micro.hs b/src/Data/Thyme/Internal/Micro.hs
--- a/src/Data/Thyme/Internal/Micro.hs
+++ b/src/Data/Thyme/Internal/Micro.hs
@@ -19,6 +19,10 @@
 import Data.Int
 import Data.Ix
 import Data.Ratio
+import Data.Vector.Generic (Vector)
+import Data.Vector.Generic.Mutable (MVector)
+import qualified Data.Vector.Unboxed as VU
+import qualified Data.Vector.Unboxed.Mutable as VUM
 import Data.VectorSpace
 import GHC.Generics (Generic)
 import System.Random
@@ -70,13 +74,13 @@
     {-# INLINE zeroV #-}
     zeroV = Micro 0
     {-# INLINE (^+^) #-}
-    Micro a ^+^ Micro b = Micro (a + b)
+    (^+^) = \ (Micro a) (Micro b) -> Micro (a + b)
     {-# INLINE negateV #-}
-    negateV (Micro a) = Micro (negate a)
+    negateV = \ (Micro a) -> Micro (negate a)
 
 instance VectorSpace Micro where
     type Scalar Micro = Rational
-    {-# INLINE (*^) #-}
+    {-# INLINEABLE (*^) #-}
     s *^ Micro a = Micro . fromInteger $
         case compare (2 * abs r) (denominator s) of
             LT -> n
@@ -89,9 +93,9 @@
 instance HasBasis Micro where
     type Basis Micro = ()
     {-# INLINE basisValue #-}
-    basisValue () = Micro 1000000
+    basisValue = \ _ -> Micro 1000000
     {-# INLINE decompose #-}
-    decompose (Micro a) = [((), fromIntegral a % 1000000)]
+    decompose = \ (Micro a) -> [((), fromIntegral a % 1000000)]
     {-# INLINE decompose' #-}
-    decompose' (Micro a) = const (fromIntegral a % 1000000)
+    decompose' = \ (Micro a) _ -> fromIntegral a % 1000000
 
diff --git a/tests/bench.hs b/tests/bench.hs
--- a/tests/bench.hs
+++ b/tests/bench.hs
@@ -25,6 +25,7 @@
 import qualified Data.Time.Calendar.WeekDate as T
 import qualified Data.Time.Calendar.MonthDay as T
 import qualified Data.Time.Clock.POSIX as T
+import qualified Data.Vector as V
 import Test.QuickCheck as QC
 import Test.QuickCheck.Gen as QC
 #if MIN_VERSION_QuickCheck(2,7,0)
@@ -42,13 +43,14 @@
 {-# ANN main "HLint: ignore Use list literal" #-}
 main :: IO ()
 main = do
-    utcs <- unGen (vectorOf samples arbitrary)
+    -- unboxed vectors made things a little too unfair for time
+    utcs <- fmap V.fromList $ unGen (vectorOf samples arbitrary)
 #if MIN_VERSION_QuickCheck(2,7,0)
         <$> QC.newQCGen <*> pure 0
 #else
         <$> newStdGen <*> pure 0
 #endif
-    let utcs' = review thyme <$> (utcs :: [UTCTime])
+    let utcs' = review thyme <$> utcs
     now <- getCurrentTime
     let now' = thyme # now
     let strs = T.formatTime defaultTimeLocale spec <$> utcs'
@@ -60,6 +62,8 @@
     let years' = (\ (y, _m, _d) -> y) . T.toGregorian <$> days'
     let mons = ((isLeapYear . ymdYear) &&& ymdMonth) . view gregorian <$> days
     let ords = ((isLeapYear . odYear) &&& odDay) . view ordinalDate <$> days
+    let pxs = utcTimeToPOSIXSeconds <$> utcs
+    let pxs' = T.utcTimeToPOSIXSeconds <$> utcs'
 
     let config = defaultConfig {cfgVerbosity = Last (Just Quiet)}
     (exit . and <=< withConfig config) $ do
@@ -112,6 +116,11 @@
             ( "utcTimeToPOSIXSeconds", 10
                 , nf (utcTimeToPOSIXSeconds <$>) utcs
                 , nf (T.utcTimeToPOSIXSeconds <$>) utcs' ) :
+
+            -- toSeconds
+            ( "toSeconds", 45
+                , nf ((toSeconds :: NominalDiffTime -> Double) <$>) pxs
+                , nf ((realToFrac :: T.NominalDiffTime -> Double) <$>) pxs' ) :
 
             -- LocalTime
             ( "timeToTimeOfDay", 40
diff --git a/thyme.cabal b/thyme.cabal
--- a/thyme.cabal
+++ b/thyme.cabal
@@ -1,5 +1,5 @@
 name:           thyme
-version:        0.3.3.0
+version:        0.3.4.0
 synopsis:       A faster time library
 description:
     Thyme is a rewrite of the fine @time@ library, with a particular focus
@@ -175,6 +175,7 @@
         random,
         thyme,
         time,
+        vector,
         vector-space
     if flag(lens)
         build-depends: lens