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
@@ -20,6 +20,7 @@
 import Control.Lens
 import Control.Monad
 import Data.AffineSpace
+import Data.Bits ((.&.))
 import Data.Data
 import Data.Int
 import Data.Ix
@@ -27,10 +28,8 @@
 import Data.Vector.Unboxed (Vector)
 import qualified Data.Vector.Unboxed as V
 import GHC.Generics (Generic)
-import GHC.Prim
-import GHC.Types
 import System.Random
-import Test.QuickCheck
+import Test.QuickCheck hiding ((.&.))
 
 type Years = Int
 type Months = Int
@@ -105,13 +104,8 @@
 
 -- | Gregorian leap year?
 isLeapYear :: Year -> Bool
-isLeapYear (I# y#) = isLeapYear# y#
-
--- | INTERNAL: avoid GHC duplicating code for each of the possibilities.
-{-# NOINLINE isLeapYear# #-}
-isLeapYear# :: Int# -> Bool
-isLeapYear# y# = remInt# y# 4# ==# 0#
-    && (remInt# y# 400# ==# 0# || remInt# y# 100# /=# 0#)
+isLeapYear y = y .&. 3 == 0 && (r100 /= 0 || q100 .&. 3 == 0) where
+    (q100, r100) = y `quotRem` 100
 
 type DayOfYear = Int
 data OrdinalDate = OrdinalDate
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
@@ -52,7 +52,7 @@
 --
 -- [@Performance@] Try to make sure @n@ is one of 'Float', 'Double', 'Int',
 -- 'Int64' or 'Integer', for which rewrite @RULES@ have been provided.
-{-# INLINE fromSeconds #-}
+{-# INLINE[0] fromSeconds #-}
 fromSeconds :: (Real n, TimeDiff t) => n -> t
 fromSeconds = fromSeconds' . toRational
 
@@ -77,11 +77,11 @@
 
 {-# RULES
 
-"fromSeconds/Float"     fromSeconds = fromSecondsRealFrac (0 :: Float)
-"fromSeconds/Double"    fromSeconds = fromSecondsRealFrac (0 :: Double)
-"fromSeconds/Int"       fromSeconds = fromSecondsIntegral (0 :: Int)
-"fromSeconds/Int64"     fromSeconds = fromSecondsIntegral (0 :: Int64)
-"fromSeconds/Integer"   fromSeconds = fromSecondsIntegral (0 :: Integer)
+"fromSeconds/Float"    [~0] fromSeconds = fromSecondsRealFrac (0 :: Float)
+"fromSeconds/Double"   [~0] fromSeconds = fromSecondsRealFrac (0 :: Double)
+"fromSeconds/Int"      [~0] fromSeconds = fromSecondsIntegral (0 :: Int)
+"fromSeconds/Int64"    [~0] fromSeconds = fromSecondsIntegral (0 :: Int64)
+"fromSeconds/Integer"  [~0] fromSeconds = fromSecondsIntegral (0 :: Integer)
 
   #-}
 
diff --git a/src/Data/Thyme/Clock/POSIX.hsc b/src/Data/Thyme/Clock/POSIX.hsc
--- a/src/Data/Thyme/Clock/POSIX.hsc
+++ b/src/Data/Thyme/Clock/POSIX.hsc
@@ -38,17 +38,22 @@
 getPOSIXTime :: IO POSIXTime
 #ifdef mingw32_HOST_OS
 
+-- On Windows, the equlvalent of POSIX time is "file time", defined as
+-- the number of 100-nanosecond intervals that have elapsed since
+-- 12:00 AM January 1, 1601 (UTC). We can convert this into a POSIX
+-- time by adjusting the offset to be relative to the POSIX epoch.
 getPOSIXTime = do
     FILETIME ft <- System.Win32.Time.getSystemTimeAsFileTime
-    return . NominalDiffTime . Micro $
-        fromIntegral ft - 116444736000000000{-win32_epoch_adjust-}
+    return . NominalDiffTime . Micro . fromIntegral $
+        quot ft 10 - 11644473600000000{-ftEpoch ^. microseconds-}
+--  ftEpoch = utcTime # UTCTime (gregorian # YearMonthDay 1601 1 1) zeroV
 
 #else
 
 getPOSIXTime = allocaBytes #{size struct timeval} $ \ ptv -> do
     throwErrnoIfMinus1_ "gettimeofday" $ gettimeofday ptv nullPtr
-    sec <- #{peek struct timeval, tv_sec} ptv :: IO CLong
-    usec <- #{peek struct timeval, tv_usec} ptv :: IO CLong
+    CTime sec <- #{peek struct timeval, tv_sec} ptv
+    CSUSeconds usec <- #{peek struct timeval, tv_usec} ptv
     return . NominalDiffTime . Micro $
         1000000 * fromIntegral sec + fromIntegral usec
 
diff --git a/src/Data/Thyme/LocalTime.hs b/src/Data/Thyme/LocalTime.hs
--- a/src/Data/Thyme/LocalTime.hs
+++ b/src/Data/Thyme/LocalTime.hs
@@ -63,7 +63,7 @@
         (minutes, g1) = randomR (timeZoneMinutes l, timeZoneMinutes u) g0
         (summer, g2) = randomR (timeZoneSummerOnly l, timeZoneSummerOnly u) g1
         -- slightly dubious interpretation of ‘range’
-        (name, g3) = foldr randChar ([], g2) . take 4 $ zipWith (,)
+        (name, g3) = foldr randChar ([], g2) . take 4 $ zip
             (timeZoneName l ++ "AAAA") (timeZoneName u ++ "ZZZZ")
         randChar nR (ns, g) = (: ns) `first` randomR nR g
     random = randomR (minBound, maxBound)
diff --git a/src/Data/Thyme/Time/Core.hs b/src/Data/Thyme/Time/Core.hs
--- a/src/Data/Thyme/Time/Core.hs
+++ b/src/Data/Thyme/Time/Core.hs
@@ -252,6 +252,14 @@
 diffUTCTime :: UTCTime -> UTCTime -> NominalDiffTime
 diffUTCTime = (.-.)
 
+{-# INLINE toMicroseconds #-}
+toMicroseconds :: (TimeDiff t) => t -> Int64
+toMicroseconds = view microseconds
+
+{-# INLINE fromMicroseconds #-}
+fromMicroseconds :: (TimeDiff t) => Int64 -> t
+fromMicroseconds = review microseconds
+
 ------------------------------------------------------------------------
 -- * @Data.Time.Clock.POSIX@
 
diff --git a/tests/Common.hs b/tests/Common.hs
--- a/tests/Common.hs
+++ b/tests/Common.hs
@@ -5,6 +5,7 @@
 import Control.Applicative
 import Control.Lens
 import Data.AdditiveGroup
+import Data.Char
 import Data.Thyme
 import Data.Thyme.Clock.POSIX
 import System.Exit
@@ -56,7 +57,7 @@
             -- , (2, pure $ spec {-aggregate-}"crXx")
             , (1, pure $ spec {-UTCTime-}"s")
             ] :: Gen (Gen String)
-        fmap (Spec . unwords) . listOf1 $ frequency
+        fmap (Spec . dropWhile isSpace . unwords) . listOf1 $ frequency
             [(16, time), (4, string), (1, pure "%%")]
       where
         spec = Gen.elements . fmap (\ c -> ['%', c])
diff --git a/tests/bench.hs b/tests/bench.hs
--- a/tests/bench.hs
+++ b/tests/bench.hs
@@ -1,3 +1,9 @@
+{-# LANGUAGE CPP #-}
+
+#if HLINT
+#include "cabal_macros.h"
+#endif
+
 import Prelude
 import Control.Arrow
 import Control.Applicative
@@ -21,9 +27,14 @@
 import qualified Data.Time.Clock.POSIX as T
 import Test.QuickCheck as QC
 import Test.QuickCheck.Gen as QC
+#if MIN_VERSION_QuickCheck(2,7,0)
+import Test.QuickCheck.Random as QC
+#endif
 import System.Locale
 
+#if !MIN_VERSION_QuickCheck(2,7,0)
 import System.Random
+#endif
 import Text.Printf
 
 import Common
@@ -31,7 +42,12 @@
 {-# ANN main "HLint: ignore Use list literal" #-}
 main :: IO ()
 main = do
-    utcs <- unGen (vectorOf samples arbitrary) <$> newStdGen <*> pure 0
+    utcs <- unGen (vectorOf samples arbitrary)
+#if MIN_VERSION_QuickCheck(2,7,0)
+        <$> QC.newQCGen <*> pure 0
+#else
+        <$> newStdGen <*> pure 0
+#endif
     let utcs' = review thyme <$> (utcs :: [UTCTime])
     now <- getCurrentTime
     let now' = thyme # now
@@ -40,6 +56,8 @@
     let dt' = thyme # dt
     let days = utctDay . unUTCTime <$> utcs
     let days' = T.utctDay <$> utcs'
+    let years = view (gregorian . _ymdYear) <$> days
+    let years' = (\ (y, _m, _d) -> y) . T.toGregorian <$> days'
     let mons = ((isLeapYear . ymdYear) &&& ymdMonth) . view gregorian <$> days
     let ords = ((isLeapYear . odYear) &&& odDay) . view ordinalDate <$> days
 
@@ -77,6 +95,10 @@
             ( "dayOfYearToMonthAndDay", 4.3
                 , nf (uncurry dayOfYearToMonthAndDay <$>) ords
                 , nf (uncurry T.dayOfYearToMonthAndDay <$>) ords ) :
+
+            ( "isLeapYear", 1.5
+                , nf (isLeapYear <$>) years
+                , nf (T.isLeapYear <$>) years' ) :
 
             -- Clock
             ( "addUTCTime", 85
diff --git a/tests/sanity.hs b/tests/sanity.hs
--- a/tests/sanity.hs
+++ b/tests/sanity.hs
@@ -42,14 +42,22 @@
 
 prop_formatTime :: Spec -> RecentTime -> Property
 prop_formatTime (Spec spec) (RecentTime t@(review thyme -> t'))
+#if MIN_VERSION_QuickCheck(2,7,0)
+        = counterexample desc (s == s') where
+#else
         = printTestCase desc (s == s') where
+#endif
     s = formatTime defaultTimeLocale spec t
     s' = T.formatTime defaultTimeLocale spec t'
     desc = "thyme: " ++ s ++ "\ntime:  " ++ s'
 
 prop_parseTime :: Spec -> RecentTime -> Property
 prop_parseTime (Spec spec) (RecentTime orig)
+#if MIN_VERSION_QuickCheck(2,7,0)
+        = counterexample desc (fmap (review thyme) t == t') where
+#else
         = printTestCase desc (fmap (review thyme) t == t') where
+#endif
     s = T.formatTime defaultTimeLocale spec (thyme # orig)
     t = parseTime defaultTimeLocale spec s :: Maybe UTCTime
     t' = T.parseTime defaultTimeLocale spec s
diff --git a/thyme.cabal b/thyme.cabal
--- a/thyme.cabal
+++ b/thyme.cabal
@@ -1,5 +1,5 @@
 name:           thyme
-version:        0.3.2.0
+version:        0.3.3.0
 synopsis:       A faster time library
 description:
     Thyme is a rewrite of the fine @time@ library, with a particular focus