diff --git a/CHANGELOG.md b/CHANGELOG.md
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+# Revision history for time-domain
+
+## 0.1.0.0 -- YYYY-mm-dd
+
+* First version. Released on an unsuspecting world.
diff --git a/LICENSE b/LICENSE
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+++ b/LICENSE
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+Copyright (c) 2021 Manuel Bärenz
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/src/Data/TimeDomain.hs b/src/Data/TimeDomain.hs
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+{- |
+This module defines the 'TimeDomain' class.
+Its instances model time,
+simulated and realtime.
+Several instances such as 'UTCTime', 'Double' and 'Integer' are supplied here.
+-}
+
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE TypeFamilies #-}
+
+module Data.TimeDomain
+  ( module Data.TimeDomain
+  , UTCTime
+  )
+  where
+
+-- time
+import Data.Time.Clock (UTCTime, diffUTCTime)
+
+{- |
+A time domain is an affine space representing a notion of time,
+such as real time, simulated time, steps, or a completely different notion.
+
+Expected law:
+
+@(t1 `diffTime` t3) `difference` (t1 `diffTime` t2) = t2 `diffTime` t3@
+-}
+class TimeDifference (Diff time) => TimeDomain time where
+  -- | The type of differences or durations between two timestamps
+  type Diff time
+
+  {- | Compute the difference between two timestamps.
+
+  Mnemonic: 'diffTime' behaves like the '(-)' operator:
+
+  @'diffTime' earlier later = later `'diffTime'` earlier@ is the duration it takes from @earlier@ to @later.
+  -}
+  diffTime :: time -> time -> Diff time
+
+{- | A type of durations, or differences betweens time stamps.
+
+For the expected law, see 'TimeDomain'.
+-}
+class TimeDifference d where
+  -- | Calculate the difference between two durations,
+  --   compatibly with 'diffTime'.
+  difference :: d -> d -> d
+
+-- | Differences between 'UTCTime's are measured in seconds.
+instance TimeDomain UTCTime where
+  type Diff UTCTime = Double
+  diffTime t1 t2 = realToFrac $ diffUTCTime t1 t2
+
+instance TimeDifference Double where
+  difference = (-)
+
+instance TimeDomain Double where
+  type Diff Double = Double
+  diffTime = (-)
+
+instance TimeDifference Float where
+  difference = (-)
+
+instance TimeDomain Float where
+  type Diff Float = Float
+  diffTime = (-)
+
+instance TimeDifference Integer where
+  difference = (-)
+
+instance TimeDomain Integer where
+  type Diff Integer = Integer
+  diffTime = (-)
+
+instance TimeDifference () where
+  difference _ _ = ()
+
+instance TimeDomain () where
+  type Diff () = ()
+  diffTime _ _ = ()
+
+-- | Any 'Num' can be wrapped to form a 'TimeDomain'.
+newtype NumTimeDomain a = NumTimeDomain { fromNumTimeDomain :: a }
+  deriving Num
+
+instance Num a => TimeDifference (NumTimeDomain a) where
+  difference = (-)
+
+instance Num a => TimeDomain (NumTimeDomain a) where
+  type Diff (NumTimeDomain a) = NumTimeDomain a
+  diffTime = (-)
diff --git a/time-domain.cabal b/time-domain.cabal
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+++ b/time-domain.cabal
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+cabal-version:      2.4
+name:               time-domain
+version:            0.1.0.0
+license:            MIT
+license-file:       LICENSE
+author:             Manuel Bärenz
+maintainer:         programming@manuelbaerenz.de
+synopsis:           A library for time domains and durations
+description:        This library mainly provides a type class, 'TimeDomain',
+                    which can be used to specify times and durations.
+                    There are some instances for standard types from @base@ and @time@.
+extra-source-files: CHANGELOG.md
+category:           FRP
+homepage:           https://github.com/turion/time-domain/
+
+library
+  exposed-modules:  Data.TimeDomain
+  build-depends:
+      base >= 4.13.0 && <= 4.17
+    , time >= 1.9
+  hs-source-dirs:   src
+  default-language: Haskell2010