Import of source files

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diff --git a/src/Utils/Time.hs b/src/Utils/Time.hs
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+{-|
+Module      : Utils.Time
+Copyright   : (c) UU, 2019
+License     : MIT
+Maintainer  : Tom Smeding
+Stability   : experimental
+Portability : POSIX, macOS, Windows
+-}
+module Utils.Time where
+
+import Data.Time.Clock
+import Data.Time.Clock.System hiding (getSystemTime)
+import qualified Data.Time.Clock.System as Sys
+import Data.Time.Format
+
+
+-- | A timestamp in milliseconds.
+newtype TimeStamp = TimeStamp Int
+  deriving (Show, Read, Eq, Ord)
+
+-- | The number of milliseconds stored in the timestamp newtype.
+timestampMS :: TimeStamp -> Int
+timestampMS (TimeStamp n) = n
+
+-- | Offset the timestamp by the given number of milliseconds.
+plusMS :: TimeStamp -> Int -> TimeStamp
+plusMS (TimeStamp n) m = TimeStamp (n + m)
+
+-- | The number of milliseconds that the first timestamp is later than the
+-- second.
+subtractMS :: TimeStamp -> TimeStamp -> Int
+subtractMS (TimeStamp n) (TimeStamp m) = n - m
+
+-- | Return the current system time as a timestamp.
+getSystemTime :: IO TimeStamp
+getSystemTime = TimeStamp . systemToMS <$> Sys.getSystemTime
+  where
+    systemToMS tm = let MkSystemTime s ns = truncateSystemTimeLeapSecond tm
+                    in fromIntegral s * 1000 + fromIntegral ns `div` 1000000
+
+-- | Show a UTCTime in ISO-8601 format.
+iso8601Show :: UTCTime -> String
+iso8601Show = formatTime defaultTimeLocale (iso8601DateFormat (Just "%H:%M:%S"))