diff --git a/Data/UnixTime/Types.hs b/Data/UnixTime/Types.hs
deleted file mode 100644
--- a/Data/UnixTime/Types.hs
+++ /dev/null
@@ -1,36 +0,0 @@
-module Data.UnixTime.Types where
-
-import Data.ByteString
-import Data.ByteString.Char8 ()
-import Data.Int
-import Foreign.C.Types
-
--- |
--- Data structure for Unix time.
-data UnixTime = UnixTime {
-    -- | Seconds from 1st Jan 1970
-    utSeconds :: {-# UNPACK #-} !CTime
-    -- | Micro seconds (i.e. 10^(-6))
-  , utMicroSeconds :: {-# UNPACK #-} !Int32
-  } deriving (Eq,Ord,Show)
-
--- |
--- Format of the strptime()/strftime() style.
-type Format = ByteString
-
--- |
--- Data structure for UnixTime diff.
---
--- >>> (3 :: UnixDiffTime) + 2
--- UnixDiffTime {udtSeconds = 5, udtMicroSecnods = 0}
--- >>> (2 :: UnixDiffTime) - 5
--- UnixDiffTime {udtSeconds = -3, udtMicroSecnods = 0}
--- >>> (3 :: UnixDiffTime) * 2
--- UnixDiffTime {udtSeconds = 6, udtMicroSecnods = 0}
-
-data UnixDiffTime = UnixDiffTime {
-    -- | Seconds from 1st Jan 1970
-    udtSeconds :: {-# UNPACK #-} !CTime
-    -- | Micro seconds (i.e. 10^(-6))
-  , udtMicroSecnods :: {-# UNPACK #-} !Int32
-  } deriving (Eq,Ord,Show)
diff --git a/Data/UnixTime/Types.hsc b/Data/UnixTime/Types.hsc
new file mode 100644
--- /dev/null
+++ b/Data/UnixTime/Types.hsc
@@ -0,0 +1,52 @@
+module Data.UnixTime.Types where
+
+import Control.Applicative ((<$>), (<*>))
+import Data.ByteString
+import Data.ByteString.Char8 ()
+import Data.Int
+import Foreign.C.Types
+import Foreign.Storable
+
+#include <sys/time.h>
+
+#let alignment t = "%lu", (unsigned long)offsetof(struct {char x__; t (y__); }, y__)
+
+-- |
+-- Data structure for Unix time.
+data UnixTime = UnixTime {
+    -- | Seconds from 1st Jan 1970
+    utSeconds :: {-# UNPACK #-} !CTime
+    -- | Micro seconds (i.e. 10^(-6))
+  , utMicroSeconds :: {-# UNPACK #-} !Int32
+  } deriving (Eq,Ord,Show)
+
+instance Storable UnixTime where
+    sizeOf _    = (#size struct timeval)
+    alignment _ = (#alignment struct timeval)
+    peek ptr    = UnixTime
+            <$> (#peek struct timeval, tv_sec)  ptr
+            <*> (#peek struct timeval, tv_usec) ptr
+    poke ptr ut = do
+            (#poke struct timeval, tv_sec)  ptr (utSeconds ut)
+            (#poke struct timeval, tv_usec) ptr (utMicroSeconds ut)
+
+-- |
+-- Format of the strptime()/strftime() style.
+type Format = ByteString
+
+-- |
+-- Data structure for UnixTime diff.
+--
+-- >>> (3 :: UnixDiffTime) + 2
+-- UnixDiffTime {udtSeconds = 5, udtMicroSecnods = 0}
+-- >>> (2 :: UnixDiffTime) - 5
+-- UnixDiffTime {udtSeconds = -3, udtMicroSecnods = 0}
+-- >>> (3 :: UnixDiffTime) * 2
+-- UnixDiffTime {udtSeconds = 6, udtMicroSecnods = 0}
+
+data UnixDiffTime = UnixDiffTime {
+    -- | Seconds from 1st Jan 1970
+    udtSeconds :: {-# UNPACK #-} !CTime
+    -- | Micro seconds (i.e. 10^(-6))
+  , udtMicroSecnods :: {-# UNPACK #-} !Int32
+  } deriving (Eq,Ord,Show)
diff --git a/test/UnixTimeSpec.hs b/test/UnixTimeSpec.hs
--- a/test/UnixTimeSpec.hs
+++ b/test/UnixTimeSpec.hs
@@ -8,6 +8,9 @@
 import Data.Time
 import Data.Time.Clock.POSIX (posixSecondsToUTCTime)
 import Data.UnixTime
+import Foreign.Ptr (Ptr)
+import Foreign.Marshal.Alloc (alloca)
+import Foreign.Storable (peek, poke)
 import System.Locale (defaultTimeLocale)
 import Test.Hspec
 import Test.Hspec.QuickCheck (prop)
@@ -48,6 +51,12 @@
             let ut0' = addUnixDiffTime ut1 $ diffUnixTime ut0 ut1
                 ut1' = addUnixDiffTime ut0 $ diffUnixTime ut1 ut0
             in ut0' == ut0 && ut1' == ut1
+
+    describe "UnixTime Storable instance" $
+        prop "peek . poke = id" $ \ut ->
+            let pokePeek :: Ptr UnixTime -> IO UnixTime
+                pokePeek ptr = poke ptr ut >> peek ptr
+            in shouldReturn (alloca pokePeek) ut
 
 formatMailModel :: UTCTime -> TimeZone -> ByteString
 formatMailModel ut zone = BS.pack $ formatTime defaultTimeLocale fmt zt
diff --git a/unix-time.cabal b/unix-time.cabal
--- a/unix-time.cabal
+++ b/unix-time.cabal
@@ -1,5 +1,5 @@
 Name:                   unix-time
-Version:                0.2.0
+Version:                0.2.1
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3