diff --git a/src/Network/Wai/Middleware/Prometheus.hs b/src/Network/Wai/Middleware/Prometheus.hs
--- a/src/Network/Wai/Middleware/Prometheus.hs
+++ b/src/Network/Wai/Middleware/Prometheus.hs
@@ -11,15 +11,16 @@
 ,   metricsApp
 ) where
 
-import Data.Time.Clock (UTCTime, diffUTCTime, getCurrentTime)
 import qualified Data.ByteString.Builder as BS
 import qualified Data.ByteString.Char8 as BS
 import qualified Data.Default as Default
 import Data.Maybe (fromMaybe)
+import Data.Ratio ((%))
 import qualified Data.Text as T
 import qualified Network.HTTP.Types as HTTP
 import qualified Network.Wai as Wai
 import qualified Prometheus as Prom
+import System.Clock (Clock(..), TimeSpec, diffTimeSpec, getTime, toNanoSecs)
 
 
 -- | Settings that control the behavior of the Prometheus middleware.
@@ -48,11 +49,11 @@
 {-# NOINLINE requestLatency #-}
 -- XXX: https://prometheus.io/docs/practices/naming/ says this should be
 -- _seconds, not _microseconds.
-requestLatency :: Prom.Metric (Prom.Vector Prom.Label3 Prom.Summary)
+requestLatency :: Prom.Metric (Prom.Vector Prom.Label3 Prom.Histogram)
 requestLatency = Prom.unsafeRegisterIO $ Prom.vector ("handler", "method", "status_code")
-                                       $ Prom.summary info Prom.defaultQuantiles
-    where info = Prom.Info "http_request_duration_microseconds"
-                           "The HTTP request latencies in microseconds."
+                                       $ Prom.histogram info Prom.defaultBuckets
+    where info = Prom.Info "http_request_duration_seconds"
+                           "The HTTP request latencies in seconds."
 
 -- | Instrument a WAI app with the default WAI metrics.
 --
@@ -63,12 +64,12 @@
               -> Wai.Application  -- ^ The app to instrument
               -> Wai.Application  -- ^ The instrumented app
 instrumentApp handler app req respond = do
-    start <- getCurrentTime
+    start <- getTime Monotonic
     app req $ \res -> do
-        end <- getCurrentTime
+        end <- getTime Monotonic
         let method = Just $ BS.unpack (Wai.requestMethod req)
         let status = Just $ show (HTTP.statusCode (Wai.responseStatus res))
-        observeMicroSeconds handler method status start end
+        observeSeconds handler method status start end
         respond res
 
 -- | Instrument an IO action with timing metrics. This function can be used if
@@ -82,15 +83,15 @@
              -> IO a    -- ^ The IO action to instrument
              -> IO a    -- ^ The instrumented app
 instrumentIO label io = do
-    start  <- getCurrentTime
+    start  <- getTime Monotonic
     result <- io
-    end    <- getCurrentTime
-    observeMicroSeconds label Nothing Nothing start end
+    end    <- getTime Monotonic
+    observeSeconds label Nothing Nothing start end
     return result
 
-observeMicroSeconds :: String -> Maybe String -> Maybe String -> UTCTime -> UTCTime -> IO ()
-observeMicroSeconds handler method status start end = do
-    let latency = fromRational $ toRational (end `diffUTCTime` start) * 1000000
+observeSeconds :: String -> Maybe String -> Maybe String -> TimeSpec -> TimeSpec -> IO ()
+observeSeconds handler method status start end = do
+    let latency = fromRational $ toRational (toNanoSecs (end `diffTimeSpec` start) % 1000000000)
     Prom.withLabel (handler, fromMaybe "" method, fromMaybe "" status)
                    (Prom.observe latency)
                    requestLatency
diff --git a/wai-middleware-prometheus.cabal b/wai-middleware-prometheus.cabal
--- a/wai-middleware-prometheus.cabal
+++ b/wai-middleware-prometheus.cabal
@@ -1,5 +1,5 @@
 name:                wai-middleware-prometheus
-version:             0.1.1
+version:             0.2.0
 synopsis:
     WAI middlware for exposing http://prometheus.io metrics.
 description:
@@ -26,11 +26,11 @@
   build-depends:
       base               >=4.7 && <5
     , bytestring         >=0.9
+    , clock
     , data-default
     , http-types
     , prometheus-client
     , text               >=0.11
-    , time
     , wai                >=3.0
   ghc-options: -Wall