diff --git a/Data/Micro.hs b/Data/Micro.hs
--- a/Data/Micro.hs
+++ b/Data/Micro.hs
@@ -27,8 +27,10 @@
 deriving instance Show Micro
 #else
 instance Show Micro where
-    show (Micro a) = printf "%d.%06u" q r where
-        (q, r) = divMod a 1000000
+    show (Micro a) = case compare a 0 of
+        LT -> printf "-%d.%06u" `uncurry` quotRem (negate a) 1000000
+        EQ -> "0"
+        GT -> printf "%d.%06u" `uncurry` quotRem a 1000000
 #endif
 
 {-# INLINE toMicro #-}
@@ -52,6 +54,10 @@
     signum (Micro a) = Micro (signum a * 1000000)
     fromInteger a = Micro (fromInteger a * 1000000)
 
+instance Real Micro where
+    {-# INLINE toRational #-}
+    toRational (Micro a) = toInteger a % 1000000
+
 instance Fractional Micro where
     {-# INLINE (/) #-}
     {-# INLINE recip #-}
@@ -60,14 +66,22 @@
     recip (Micro a) = Micro (quot 1000000 a)
     fromRational = toMicro
 
--- TODO: instance Real Micro
--- TODO: instance RealFrac Micro
+instance RealFrac Micro where
+    {-# INLINE properFraction #-}
+    properFraction a = (fromIntegral q, r) where
+        (q, r) = microQuotRem a (Micro 1000000)
 #endif
 
+{-# INLINE microQuotRem #-}
 microQuotRem :: Micro -> Micro -> (Int64, Micro)
 microQuotRem (Micro a) (Micro b) = (n, Micro f) where
     (n, f) = quotRem a b
 
+-- for when we'd rather not depend on RealFrac
+{-# INLINE microTruncate #-}
+microTruncate :: Micro -> Int
+microTruncate a = fromIntegral . fst . microQuotRem a $ Micro 1000000
+
 instance AdditiveGroup Micro where
     {-# INLINE zeroV #-}
     zeroV = Micro 0
@@ -85,7 +99,7 @@
 instance HasBasis Micro where
     type Basis Micro = ()
     {-# INLINE basisValue #-}
-    basisValue () = 1
+    basisValue () = Micro 1000000
     {-# INLINE decompose #-}
     decompose (Micro a) = [((), fromIntegral a % 1000000)]
     {-# INLINE decompose' #-}
diff --git a/Data/Thyme.hs b/Data/Thyme.hs
--- a/Data/Thyme.hs
+++ b/Data/Thyme.hs
@@ -1,11 +1,12 @@
 module Data.Thyme
     ( module Data.Thyme.Calendar
     , module Data.Thyme.Clock
+    , module Data.Thyme.Format
     , module Data.Thyme.LocalTime
     ) where
 
 import Data.Thyme.Calendar
 import Data.Thyme.Clock
--- TODO: Data.Thyme.Format
+import Data.Thyme.Format
 import Data.Thyme.LocalTime
 
diff --git a/Data/Thyme/Calendar.hs b/Data/Thyme/Calendar.hs
--- a/Data/Thyme/Calendar.hs
+++ b/Data/Thyme/Calendar.hs
@@ -1,23 +1,25 @@
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE ViewPatterns #-}
+
 module Data.Thyme.Calendar (
     -- * Days
       Day (..)
     -- * Gregorian calendar
     , Year, Month, DayOfMonth
     , YearMonthDay (..)
-    , module Data.Thyme.Calendar
     , isLeapYear
-    -- * Lenses
-    , _toModifiedJulianDay
-    , _ymdYear, _ymdMonth, _ymdDay
+    , module Data.Thyme.Calendar
     ) where
 
 import Prelude hiding ((.))
 import Control.Applicative
 import Control.Category
 import Control.Lens
-import Data.Thyme.Calendar.Day
 import Data.Thyme.Calendar.OrdinalDate
 import Data.Thyme.Calendar.MonthDay
+import Data.Thyme.Calendar.Internal
+import Data.Thyme.Format.Internal
+import Data.Thyme.TH
 
 {-# INLINE gregorian #-}
 gregorian :: Simple Iso Day YearMonthDay
@@ -38,7 +40,10 @@
 fromGregorianValid (YearMonthDay y m d) = review ordinalDate . OrdinalDate y
     <$> monthDayToDayOfYearValid (isLeapYear y) (MonthDay m d)
 
--- TODO: showGregorian
+{-# INLINEABLE showGregorian #-}
+showGregorian :: Day -> String
+showGregorian (view gregorian -> YearMonthDay y m d) =
+    shows04 y . (:) '-' . shows02 m . (:) '-' . shows02 d $ ""
 
 {-# INLINE gregorianMonthLength #-}
 gregorianMonthLength :: Year -> Month -> Int
@@ -46,4 +51,8 @@
 
 -- TODO: addGregorianMonthsClip addGregorianMonthsRollover
 -- TODO: addGregorianYearsClip addGregorianYearsRollover
+
+-- * Lenses
+thymeLenses ''Day
+thymeLenses ''YearMonthDay
 
diff --git a/Data/Thyme/Calendar/Day.hs b/Data/Thyme/Calendar/Day.hs
deleted file mode 100644
--- a/Data/Thyme/Calendar/Day.hs
+++ /dev/null
@@ -1,54 +0,0 @@
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE TypeFamilies #-}
-
--- #hide
-module Data.Thyme.Calendar.Day where
-
-import Prelude
-import Control.DeepSeq
-import Data.AffineSpace
-import Data.Data
-import Data.Int
-import Data.Ix
-import Data.Thyme.TH
-
--- | The Modified Julian Day is a standard count of days, with zero being
--- the day 1858-11-17.
-newtype Day = ModifiedJulianDay
-    { toModifiedJulianDay :: Int64
-    } deriving (Eq, Ord, Enum, Ix, Bounded, NFData, Data, Typeable)
-
-thymeLenses ''Day
-
-#if 1 /*SHOW_INTERNAL*/
-deriving instance Show Day
-#endif
-
-instance AffineSpace Day where
-    type Diff Day = Int
-    {-# INLINE (.-.) #-}
-    ModifiedJulianDay a .-. ModifiedJulianDay b = fromIntegral (a - b)
-    {-# INLINE (.+^) #-}
-    ModifiedJulianDay a .+^ d = ModifiedJulianDay (a + fromIntegral d)
-
-------------------------------------------------------------------------
-
-type Year = Int
-type DayOfYear = Int
-type Month = Int
-type DayOfMonth = Int
-
-data YearMonthDay = YearMonthDay
-    { ymdYear :: {-# UNPACK #-}!Year
-    , ymdMonth :: {-# UNPACK #-}!Month
-    , ymdDay :: {-# UNPACK #-}!DayOfMonth
-    } deriving (Eq, Ord, Data, Typeable, Show)
-
-thymeLenses ''YearMonthDay
-
-instance NFData YearMonthDay
-
diff --git a/Data/Thyme/Calendar/Internal.hs b/Data/Thyme/Calendar/Internal.hs
new file mode 100644
--- /dev/null
+++ b/Data/Thyme/Calendar/Internal.hs
@@ -0,0 +1,142 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeFamilies #-}
+
+-- #hide
+module Data.Thyme.Calendar.Internal where
+
+import Prelude
+import Control.DeepSeq
+import Control.Lens
+import Data.AffineSpace
+import Data.Data
+import Data.Int
+import Data.Ix
+
+-- | The Modified Julian Day is a standard count of days, with zero being
+-- the day 1858-11-17.
+newtype Day = ModifiedJulianDay
+    { toModifiedJulianDay :: Int64
+    } deriving (Eq, Ord, Enum, Ix, Bounded, NFData, Data, Typeable)
+
+#if 1 /*SHOW_INTERNAL*/
+deriving instance Show Day
+#endif
+
+instance AffineSpace Day where
+    type Diff Day = Int
+    {-# INLINE (.-.) #-}
+    ModifiedJulianDay a .-. ModifiedJulianDay b = fromIntegral (a - b)
+    {-# INLINE (.+^) #-}
+    ModifiedJulianDay a .+^ d = ModifiedJulianDay (a + fromIntegral d)
+
+------------------------------------------------------------------------
+
+type Year = Int
+type Month = Int
+type DayOfMonth = Int
+
+data YearMonthDay = YearMonthDay
+    { ymdYear :: {-# UNPACK #-}!Year
+    , ymdMonth :: {-# UNPACK #-}!Month
+    , ymdDay :: {-# UNPACK #-}!DayOfMonth
+    } deriving (Eq, Ord, Data, Typeable, Show)
+
+instance NFData YearMonthDay
+
+------------------------------------------------------------------------
+
+-- | Gregorian leap year?
+{-# INLINE isLeapYear #-}
+isLeapYear :: Year -> Bool
+isLeapYear y = mod y 4 == 0 && (mod y 400 == 0 || mod y 100 /= 0)
+
+type DayOfYear = Int
+data OrdinalDate = OrdinalDate
+    { odYear :: {-# UNPACK #-}!Year
+    , odDay :: {-# UNPACK #-}!DayOfYear
+    } deriving (Eq, Ord, Data, Typeable, Show)
+
+instance NFData OrdinalDate
+
+{-# INLINE ordinalDate #-}
+ordinalDate :: Simple Iso Day OrdinalDate
+ordinalDate = iso toOrd fromOrd where
+
+    {-# INLINEABLE toOrd #-}
+    toOrd :: Day -> OrdinalDate
+    toOrd (ModifiedJulianDay mjd) = OrdinalDate
+            (fromIntegral year) (fromIntegral yd) where
+        -- pilfered
+        a = mjd + 678575
+        quadcent = div a 146097
+        b = mod a 146097
+        cent = min (div b 36524) 3
+        c = b - cent * 36524
+        quad = div c 1461
+        d = mod c 1461
+        y = min (div d 365) 3
+        yd = d - y * 365 + 1
+        year = quadcent * 400 + cent * 100 + quad * 4 + y + 1
+
+    {-# INLINEABLE fromOrd #-}
+    fromOrd :: OrdinalDate -> Day
+    fromOrd (OrdinalDate year yd) = ModifiedJulianDay mjd where
+        -- pilfered
+        y = fromIntegral (year - 1)
+        mjd = 365 * y + div y 4 - div y 100 + div y 400 - 678576
+            + clip 1 (if isLeapYear year then 366 else 365) (fromIntegral yd)
+        clip a b = max a . min b
+
+------------------------------------------------------------------------
+
+type Week = Int
+type DayOfWeek = Int
+data WeekDate = WeekDate
+    { wdYear :: {-# UNPACK #-}!Year
+    , wdWeek :: {-# UNPACK #-}!Week
+    , wdDay :: {-# UNPACK #-}!DayOfWeek
+    } deriving (Eq, Ord, Data, Typeable, Show)
+
+instance NFData WeekDate
+
+-- | Accepts 0-based 'DayOfWeek' and 'Week' when 'review'ing.
+{-# INLINE weekDate #-}
+weekDate :: Simple Iso Day WeekDate
+weekDate = iso toWeek fromWeek where
+
+    {-# INLINEABLE toWeek #-}
+    toWeek :: Day -> WeekDate
+    toWeek day@(ModifiedJulianDay mjd) = WeekDate
+            y1 (fromIntegral $ w1 + 1) (fromIntegral $ mod d 7 + 1) where
+        -- pilfered and refactored; no idea what foo and bar mean
+        OrdinalDate y0 yd = view ordinalDate day
+        d = mjd + 2
+        foo :: Year -> {-Week-1-}Int64
+        foo y = bar $ review ordinalDate (OrdinalDate y 6)
+        bar :: Day -> {-Week-1-}Int64
+        bar (ModifiedJulianDay k) = div d 7 - div k 7
+        w0 = bar $ ModifiedJulianDay (d - fromIntegral yd + 4)
+        (y1, w1) = case w0 of
+            -1 -> (y0 - 1, foo (y0 - 1))
+            52 | foo (y0 + 1) == 0 -> (y0 + 1, 0)
+            _ -> (y0, w0)
+
+    {-# INLINEABLE fromWeek #-}
+    fromWeek :: WeekDate -> Day
+    fromWeek wd@(WeekDate y _ _) = fromWeekMax wMax wd where
+        WeekDate _ wMax _ = toWeek $ review ordinalDate (OrdinalDate y 365)
+
+{-# INLINE fromWeekMax #-}
+fromWeekMax :: Week -> WeekDate -> Day
+fromWeekMax wMax (WeekDate y w d) = ModifiedJulianDay mjd where
+    -- pilfered and refactored
+    ModifiedJulianDay k = review ordinalDate (OrdinalDate y 6)
+    -- FIXME: Is it okay to clip d to 0 in the case of Sunday-starting
+    -- weeks, and clip w to 0 for OrdinalDate.{sun,mon}dayStartWeek?
+    mjd = k - mod k 7 - 10 + clip 0 7 (fromIntegral d)
+        + fromIntegral (clip 0 wMax w) * 7
+    clip a b = max a . min b
+
diff --git a/Data/Thyme/Calendar/MonthDay.hs b/Data/Thyme/Calendar/MonthDay.hs
--- a/Data/Thyme/Calendar/MonthDay.hs
+++ b/Data/Thyme/Calendar/MonthDay.hs
@@ -14,7 +14,7 @@
 import Control.Monad
 import Data.Data
 import qualified Data.Time.Calendar.MonthDay as T
-import Data.Thyme.Calendar.Day
+import Data.Thyme.Calendar.Internal
 import Data.Thyme.TH
 
 data MonthDay = MonthDay
diff --git a/Data/Thyme/Calendar/OrdinalDate.hs b/Data/Thyme/Calendar/OrdinalDate.hs
--- a/Data/Thyme/Calendar/OrdinalDate.hs
+++ b/Data/Thyme/Calendar/OrdinalDate.hs
@@ -3,7 +3,8 @@
 -- | ISO 8601 Ordinal Date format
 
 module Data.Thyme.Calendar.OrdinalDate
-    ( Year, DayOfYear
+    ( Year, isLeapYear
+    , DayOfYear, OrdinalDate (..), ordinalDate
     , module Data.Thyme.Calendar.OrdinalDate
     ) where
 
@@ -11,53 +12,45 @@
 import Control.Applicative
 import Control.Lens
 import Control.Monad
-import Data.Thyme.Calendar.Day
+import Data.Thyme.Calendar.Internal
 import Data.Thyme.TH
 
-data OrdinalDate = OrdinalDate
-    { odYear :: {-# UNPACK #-}!Year
-    , odDay :: {-# UNPACK #-}!DayOfYear }
-
-{-# INLINE ordinalDate #-}
-ordinalDate :: Simple Iso Day OrdinalDate
-ordinalDate = iso toOrd fromOrd where
-
-    {-# INLINEABLE toOrd #-}
-    toOrd :: Day -> OrdinalDate
-    toOrd (ModifiedJulianDay mjd) = OrdinalDate
-            (fromIntegral year) (fromIntegral yd) where
-        -- pilfered
-        a = mjd + 678575
-        quadcent = div a 146097
-        b = mod a 146097
-        cent = min (div b 36524) 3
-        c = b - cent * 36524
-        quad = div c 1461
-        d = mod c 1461
-        y = min (div d 365) 3
-        yd = d - y * 365 + 1
-        year = quadcent * 400 + cent * 100 + quad * 4 + y + 1
-
-    {-# INLINEABLE fromOrd #-}
-    fromOrd :: OrdinalDate -> Day
-    fromOrd (OrdinalDate year yd) = ModifiedJulianDay mjd where
-        -- pilfered
-        y = fromIntegral (year - 1)
-        mjd = 365 * y + div y 4 - div y 100 + div y 400 - 678576
-            + clip 1 (if isLeapYear year then 366 else 365) (fromIntegral yd)
-        clip a b = max a . min b
-
 {-# INLINE fromOrdinalDateValid #-}
 fromOrdinalDateValid :: OrdinalDate -> Maybe Day
 fromOrdinalDateValid od@(OrdinalDate y d) = review ordinalDate od
     <$ guard (1 <= d && d <= if isLeapYear y then 366 else 365)
 
-{-# INLINE isLeapYear #-}
-isLeapYear :: Year -> Bool
-isLeapYear y = mod y 4 == 0 && (mod y 400 == 0 || mod y 100 /= 0)
+-- | Use @'review' 'weekDate'@ to convert back to 'Day'.
+{-# INLINE sundayStartWeek #-}
+sundayStartWeek :: Day -> WeekDate
+sundayStartWeek day@(ModifiedJulianDay mjd) = WeekDate y
+        (fromIntegral $ div d 7 - div k 7) (fromIntegral $ mod d 7) where
+    OrdinalDate y yd = view ordinalDate day
+    d = mjd + 3
+    k = d - fromIntegral yd
 
--- TODO: mondayStartWeek fromMondayStartWeek fromMondayStartWeekValid
--- TODO: sundayStartWeek fromSundayStartWeek fromSundayStartWeekValid
+-- | Accepts 0−6 for 'DayOfWeek', and 0-based 'Week's.
+{-# INLINEABLE fromSundayStartWeekValid #-}
+fromSundayStartWeekValid :: WeekDate -> Maybe Day
+fromSundayStartWeekValid wd@(WeekDate y w d) = fromWeekMax wMax wd
+        <$ guard (0 <= d && d <= 6 && 0 <= w && w <= wMax) where
+    WeekDate _ wMax _ = view (from ordinalDate . weekDate) (OrdinalDate y 365)
+
+-- | Use @'review' 'weekDate'@ to convert back to 'Day'.
+{-# INLINE mondayStartWeek #-}
+mondayStartWeek :: Day -> WeekDate
+mondayStartWeek day@(ModifiedJulianDay mjd) = WeekDate y
+        (fromIntegral $ div d 7 - div k 7) (fromIntegral $ mod d 7 + 1) where
+    OrdinalDate y yd = view ordinalDate day
+    d = mjd + 2
+    k = d - fromIntegral yd
+
+-- | Accepts 1−7 for 'DayOfWeek', and 0-based 'Week's.
+{-# INLINEABLE fromMondayStartWeekValid #-}
+fromMondayStartWeekValid :: WeekDate -> Maybe Day
+fromMondayStartWeekValid wd@(WeekDate y w d) = fromWeekMax wMax wd
+        <$ guard (1 <= d && d <= 7 && 0 <= w && w <= wMax) where
+    WeekDate _ wMax _ = view (from ordinalDate . weekDate) (OrdinalDate y 365)
 
 -- * Lenses
 thymeLenses ''OrdinalDate
diff --git a/Data/Thyme/Calendar/WeekDate.hs b/Data/Thyme/Calendar/WeekDate.hs
--- a/Data/Thyme/Calendar/WeekDate.hs
+++ b/Data/Thyme/Calendar/WeekDate.hs
@@ -2,62 +2,26 @@
 {-# LANGUAGE TemplateHaskell #-}
 
 -- | ISO 8601 Week Date format
-module Data.Thyme.Calendar.WeekDate where
+module Data.Thyme.Calendar.WeekDate
+    ( Year, Week, DayOfWeek
+    , WeekDate (..), weekDate
+    , module Data.Thyme.Calendar.WeekDate
+    ) where
 
 import Prelude
 import Control.Applicative
 import Control.Lens
 import Control.Monad
-import Data.Data
-import Data.Int
-import Data.Thyme.Calendar.Day
 import Data.Thyme.Calendar.OrdinalDate
+import Data.Thyme.Calendar.Internal
 import Data.Thyme.TH
 import Text.Printf
 
-type Week = Int
-type DayOfWeek = Int
-data WeekDate = WeekDate
-    { wdYear :: {-# UNPACK #-}!Year
-    , wdWeek :: {-# UNPACK #-}!Week
-    , wdDay :: {-# UNPACK #-}!DayOfWeek
-    } deriving (Eq, Ord, Data, Typeable, Show)
-
-{-# INLINE weekDate #-}
-weekDate :: Simple Iso Day WeekDate
-weekDate = iso toWeek fromWeek where
-
-    {-# INLINEABLE toWeek #-}
-    toWeek :: Day -> WeekDate
-    toWeek day@(ModifiedJulianDay mjd) = WeekDate
-            y1 (fromIntegral $ w1 + 1) (fromIntegral $ mod d 7 + 1) where
-        -- pilfered and refactored; no idea what foo and bar mean
-        OrdinalDate y0 yd = view ordinalDate day
-        d = mjd + 2
-        foo :: Year -> Int64
-        foo y = bar $ review ordinalDate (OrdinalDate y 6)
-        bar :: Day -> Int64
-        bar (ModifiedJulianDay k) = div d 7 - div k 7
-        w0 = bar $ ModifiedJulianDay (d - fromIntegral yd + 4)
-        (y1, w1) = case w0 of
-            -1 -> (y0 - 1, foo (y0 - 1))
-            52 | foo (y0 + 1) == 0 -> (y0 + 1, 0)
-            _ -> (y0, w0)
-
-    {-# INLINEABLE fromWeek #-}
-    fromWeek :: WeekDate -> Day
-    fromWeek (WeekDate y w wd) = ModifiedJulianDay mjd where
-        -- pilfered and refactored
-        ModifiedJulianDay k = review ordinalDate (OrdinalDate y 6)
-        WeekDate _ wMax _ = toWeek $ review ordinalDate (OrdinalDate y 365)
-        mjd = k - mod k 7 - 10 + clip 1 7 (fromIntegral wd)
-            + fromIntegral (clip 1 wMax w) * 7
-        clip a b = max a . min b
-
+-- | Rejects 0-based 'DayOfWeek' and 'Week'.
+{-# INLINEABLE fromWeekDateValid #-}
 fromWeekDateValid :: WeekDate -> Maybe Day
-fromWeekDateValid wd@(WeekDate y w d) = review weekDate wd
+fromWeekDateValid wd@(WeekDate y w d) = fromWeekMax wMax wd
         <$ guard (1 <= d && d <= 7 && 1 <= w && w <= wMax) where
-    -- TODO: inline fromWeek so we can share wMax?
     WeekDate _ wMax _ = view (from ordinalDate . weekDate) (OrdinalDate y 365)
 
 {-# INLINEABLE showWeekDate #-}
diff --git a/Data/Thyme/Clock/POSIX.hs b/Data/Thyme/Clock/POSIX.hs
--- a/Data/Thyme/Clock/POSIX.hs
+++ b/Data/Thyme/Clock/POSIX.hs
@@ -7,8 +7,9 @@
 import Control.Lens
 import Data.AdditiveGroup
 import Data.AffineSpace
+import Data.Micro
 import qualified Data.Time.Clock.POSIX as T
-import Data.Thyme.Calendar.Day
+import Data.Thyme.Calendar.Internal
 import Data.Thyme.Clock.Scale
 import Data.Thyme.Clock.UTC
 
@@ -28,8 +29,8 @@
     fromPOSIX (NominalDiffTime d) = review utcTime $
         UTCTime unixEpochDay (DiffTime d)
 
--- TODO: reimplement without 'T.getPOSIXTime' to avoid 'realToFrac'?
+-- TODO: reimplement without 'T.getPOSIXTime' to avoid 'Integer'?
 {-# INLINE getPOSIXTime #-}
 getPOSIXTime :: IO POSIXTime
-getPOSIXTime = fmap realToFrac T.getPOSIXTime
+getPOSIXTime = fmap (NominalDiffTime . toMicro . toRational) T.getPOSIXTime
 
diff --git a/Data/Thyme/Clock/Scale.hs b/Data/Thyme/Clock/Scale.hs
--- a/Data/Thyme/Clock/Scale.hs
+++ b/Data/Thyme/Clock/Scale.hs
@@ -37,7 +37,7 @@
 instance HasBasis DiffTime where
     type Basis DiffTime = ()
     {-# INLINE basisValue #-}
-    basisValue () = 1
+    basisValue () = DiffTime (basisValue ())
     {-# INLINE decompose #-}
     decompose (DiffTime a) = decompose a
     {-# INLINE decompose' #-}
@@ -45,7 +45,9 @@
 
 #if INSTANCE_NUM
 deriving instance Num DiffTime
+deriving instance Real DiffTime
 deriving instance Fractional DiffTime
+deriving instance RealFrac DiffTime
 #endif
 
 {-# INLINE microsecondsToDiffTime #-}
diff --git a/Data/Thyme/Clock/UTC.hs b/Data/Thyme/Clock/UTC.hs
--- a/Data/Thyme/Clock/UTC.hs
+++ b/Data/Thyme/Clock/UTC.hs
@@ -19,7 +19,7 @@
 import Data.Int
 import Data.Ix
 import Data.Micro
-import Data.Thyme.Calendar.Day
+import Data.Thyme.Calendar.Internal
 import Data.Thyme.Clock.Scale
 import Data.VectorSpace
 
@@ -41,7 +41,7 @@
 instance HasBasis NominalDiffTime where
     type Basis NominalDiffTime = ()
     {-# INLINE basisValue #-}
-    basisValue () = 1
+    basisValue () = NominalDiffTime (basisValue ())
     {-# INLINE decompose #-}
     decompose (NominalDiffTime a) = decompose a
     {-# INLINE decompose' #-}
@@ -49,7 +49,9 @@
 
 #if INSTANCE_NUM
 deriving instance Num NominalDiffTime
+deriving instance Real NominalDiffTime
 deriving instance Fractional NominalDiffTime
+deriving instance RealFrac NominalDiffTime
 #endif
 
 {-# INLINE posixDayLength #-}
diff --git a/Data/Thyme/Format/Internal.hs b/Data/Thyme/Format/Internal.hs
new file mode 100644
--- /dev/null
+++ b/Data/Thyme/Format/Internal.hs
@@ -0,0 +1,61 @@
+module Data.Thyme.Format.Internal where
+
+import Prelude
+import Data.Micro
+
+{-# INLINE shows02 #-}
+shows02 :: Int -> String -> String
+shows02 n = if n < 10 then (:) '0' . shows n else shows n
+
+{-# INLINE show02 #-}
+show02 :: Int -> String
+show02 n = if n < 10 then '0' : show n else show n
+
+{-# INLINE show_2 #-}
+show_2 :: Int -> String
+show_2 n = if n < 10 then ' ' : show n else show n
+
+{-# INLINE show03 #-}
+show03 :: Int -> String
+show03 n = case () of
+    _ | n < 10 -> '0' : '0' : show n
+    _ | n < 100 -> '0' : show n
+    _ -> show n
+
+{-# INLINE shows04 #-}
+shows04 :: Int -> String -> String
+shows04 n = case () of
+    _ | n < 10 -> (:) '0' . (:) '0' . (:) '0' . shows n
+    _ | n < 100 -> (:) '0' . (:) '0' . shows n
+    _ | n < 1000 -> (:) '0' . shows n
+    _ -> shows n
+
+{-# INLINE show04 #-}
+show04 :: Int -> String
+show04 n = shows04 n ""
+
+{-# INLINE show60 #-}
+show60 :: Micro -> String
+show60 (Micro u) = case () of
+    _ | u < 10 -> '0' : '0' : '0' : '0' : '0' : show u
+    _ | u < 100 -> '0' : '0' : '0' : '0' : show u
+    _ | u < 1000 -> '0' : '0' : '0' : show u
+    _ | u < 10000 -> '0' : '0' : show u
+    _ | u < 100000 -> '0' : show u
+    _ -> show u
+
+{-# INLINE show6 #-}
+show6 :: Micro -> String
+show6 (Micro u) = case () of
+    _ | u == 0 -> ""
+    _ | u < 10 -> '.' : '0' : '0' : '0' : '0' : '0' : shrink u
+    _ | u < 100 -> '.' : '0' : '0' : '0' : '0' : shrink u
+    _ | u < 1000 -> '.' : '0' : '0' : '0' : shrink u
+    _ | u < 10000 -> '.' : '0' : '0' : shrink u
+    _ | u < 100000 -> '.' : '0' : shrink u
+    _ -> '.' : shrink u
+  where
+    shrink v = case divMod v 10 of
+        (w, 0) -> shrink w
+        _ -> show v
+
diff --git a/Data/Thyme/LocalTime.hs b/Data/Thyme/LocalTime.hs
--- a/Data/Thyme/LocalTime.hs
+++ b/Data/Thyme/LocalTime.hs
@@ -24,7 +24,7 @@
 import Data.Data
 import Data.Micro
 import qualified Data.Time as T
-import Data.Thyme.Calendar.Day
+import Data.Thyme.Calendar.Internal
 import Data.Thyme.Clock
 import Data.Thyme.Clock.Scale
 import Data.Thyme.Clock.UTC
@@ -50,8 +50,9 @@
 
 {-# INLINE makeTimeOfDayValid #-}
 makeTimeOfDayValid :: Hour -> Minute -> DiffTime -> Maybe TimeOfDay
-makeTimeOfDayValid h m s = TimeOfDay h m s
-    <$ guard (0 <= h && h <= 23 && 0 <= m && m <= 59 && 0 <= s && s < 61)
+makeTimeOfDayValid h m s@(DiffTime u) = TimeOfDay h m s
+    <$ guard (0 <= h && h <= 23 && 0 <= m && m <= 59)
+    <* guard (Micro 0 <= u && u < Micro 61000000)
 
 {-# INLINE timeOfDay #-}
 timeOfDay :: Simple Iso DiffTime TimeOfDay
diff --git a/thyme.cabal b/thyme.cabal
--- a/thyme.cabal
+++ b/thyme.cabal
@@ -1,5 +1,5 @@
 name:           thyme
-version:        0.1.0.0
+version:        0.1.1.0
 synopsis:       A faster time library
 description:
     A faster time library
@@ -8,10 +8,10 @@
 license-file:   LICENSE
 author:         Liyang HU
 maintainer:     thyme@liyang.hu
-copyright:      © 2013 Liyang HU
+copyright:      © 2013 Liyang HU, Ashley Yakeley
 category:       Data, System
 build-type:     Simple
-cabal-version:  >=1.8
+cabal-version:  >= 1.8
 stability:      experimental
 
 source-repository head
@@ -38,15 +38,17 @@
         Data.Thyme.LocalTime
     other-modules:
         Data.Micro
-        Data.Thyme.Calendar.Day
+        Data.Thyme.Calendar.Internal
         Data.Thyme.Clock.Scale
         Data.Thyme.Clock.UTC
+        Data.Thyme.Format.Internal
         Data.Thyme.TH
     build-depends:
-        base >= 4.6 && < 5,
+        base >= 4.5 && < 5,
         deepseq >= 1.2,
         vector-space >= 0.8,
         lens >= 3.7,
+        old-locale >= 1.0,
         template-haskell >= 2.6,
         time >= 1.4
     ghc-options: -Wall