diff --git a/src/Web/Internal/HttpApiData.hs b/src/Web/Internal/HttpApiData.hs
index 3051680..6246ed2 100644
--- a/src/Web/Internal/HttpApiData.hs
+++ b/src/Web/Internal/HttpApiData.hs
@@ -456,24 +456,31 @@ timeToUrlPiece :: FormatTime t => String -> t -> Text
 timeToUrlPiece fmt = T.pack . formatTime defaultTimeLocale (iso8601DateFormat (Just fmt))
 
 -- |
--- >>> toUrlPiece $ LocalTime (fromGregorian 2015 10 03) (TimeOfDay 14 55 01)
--- "2015-10-03T14:55:01"
+-- >>> toUrlPiece $ TimeOfDay 14 55 23.1
+-- "14:55:23.1"
+instance ToHttpApiData TimeOfDay where
+  toUrlPiece = T.pack . formatTime defaultTimeLocale "%H:%M:%S%Q"
+  toEncodedUrlPiece = unsafeToEncodedUrlPiece
+
+-- |
+-- >>> toUrlPiece $ LocalTime (fromGregorian 2015 10 03) (TimeOfDay 14 55 21.687)
+-- "2015-10-03T14:55:21.687"
 instance ToHttpApiData LocalTime where
-  toUrlPiece = timeToUrlPiece "%H:%M:%S"
+  toUrlPiece = timeToUrlPiece "%H:%M:%S%Q"
   toEncodedUrlPiece = unsafeToEncodedUrlPiece
 
 -- |
--- >>> toUrlPiece $ ZonedTime (LocalTime (fromGregorian 2015 10 03) (TimeOfDay 14 55 01)) utc
--- "2015-10-03T14:55:01+0000"
+-- >>> toUrlPiece $ ZonedTime (LocalTime (fromGregorian 2015 10 03) (TimeOfDay 14 55 51.001)) utc
+-- "2015-10-03T14:55:51.001+0000"
 instance ToHttpApiData ZonedTime where
-  toUrlPiece = timeToUrlPiece "%H:%M:%S%z"
+  toUrlPiece = timeToUrlPiece "%H:%M:%S%Q%z"
   toEncodedUrlPiece = unsafeToEncodedUrlPiece
 
 -- |
--- >>> toUrlPiece $ UTCTime (fromGregorian 2015 10 03) 864
--- "2015-10-03T00:14:24Z"
+-- >>> toUrlPiece $ UTCTime (fromGregorian 2015 10 03) 864.5
+-- "2015-10-03T00:14:24.5Z"
 instance ToHttpApiData UTCTime where
-  toUrlPiece = timeToUrlPiece "%H:%M:%SZ"
+  toUrlPiece = timeToUrlPiece "%H:%M:%S%QZ"
   toEncodedUrlPiece = unsafeToEncodedUrlPiece
 
 instance ToHttpApiData NominalDiffTime where
@@ -580,7 +587,12 @@ instance FromHttpApiData L.Text   where parseUrlPiece = Right . L.fromStrict
 -- |
 -- >>> toGregorian <$> parseUrlPiece "2016-12-01"
 -- Right (2016,12,1)
-instance FromHttpApiData Day      where parseUrlPiece = runAtto Atto.day
+instance FromHttpApiData Day where parseUrlPiece = runAtto Atto.day
+
+-- |
+-- >>> parseUrlPiece "14:55:01.333" :: Either Text TimeOfDay
+-- Right 14:55:01.333
+instance FromHttpApiData TimeOfDay where parseUrlPiece = runAtto Atto.timeOfDay
 
 -- |
 -- >>> parseUrlPiece "2015-10-03T14:55:01" :: Either Text LocalTime
diff --git a/test/Web/Internal/HttpApiDataSpec.hs b/test/Web/Internal/HttpApiDataSpec.hs
index 51e4eef..d9f3eb8 100644
--- a/test/Web/Internal/HttpApiDataSpec.hs
+++ b/test/Web/Internal/HttpApiDataSpec.hs
@@ -76,6 +76,7 @@ spec = do
     checkUrlPiece  (Proxy :: Proxy T.Text)    "Text.Strict"
     checkUrlPiece  (Proxy :: Proxy L.Text)    "Text.Lazy"
     checkUrlPiece  (Proxy :: Proxy Day)       "Day"
+    checkUrlPiece' timeOfDayGen               "TimeOfDay"
     checkUrlPiece' localTimeGen               "LocalTime"
     checkUrlPiece' zonedTimeGen               "ZonedTime"
     checkUrlPiece' utcTimeGen                 "UTCTime"
@@ -112,6 +113,7 @@ spec = do
     checkEncodedUrlPiece  (Proxy :: Proxy T.Text)    "Text.Strict"
     checkEncodedUrlPiece  (Proxy :: Proxy L.Text)    "Text.Lazy"
     checkEncodedUrlPiece  (Proxy :: Proxy Day)       "Day"
+    checkEncodedUrlPiece' timeOfDayGen               "TimeOfDay"
     checkEncodedUrlPiece' localTimeGen               "LocalTime"
     checkEncodedUrlPiece' zonedTimeGen               "ZonedTime"
     checkEncodedUrlPiece' utcTimeGen                 "UTCTime"
@@ -144,9 +146,13 @@ uuidGen = UUID.fromWords <$> arbitrary <*> arbitrary <*> arbitrary <*> arbitrary
 
 -- TODO: this generators don't generate full range items
 localTimeGen :: Gen LocalTime
-localTimeGen = LocalTime
-    <$> arbitrary
-    <*> liftA3 TimeOfDay (choose (0, 23)) (choose (0, 59)) (fromInteger <$> choose (0, 60))
+localTimeGen = LocalTime <$> arbitrary <*> timeOfDayGen
+
+timeOfDayGen :: Gen TimeOfDay
+timeOfDayGen = TimeOfDay
+  <$> choose (0, 23)
+  <*> choose (0, 59)
+  <*> fmap (\x -> 0.1 * fromInteger x) (choose (0, 600))
 
 zonedTimeGen :: Gen ZonedTime
 zonedTimeGen = ZonedTime