diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2017 Tom Sydney Kerckhove
+Copyright (c) 2016-2020 Tom Sydney Kerckhove
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/genvalidity-time.cabal b/genvalidity-time.cabal
--- a/genvalidity-time.cabal
+++ b/genvalidity-time.cabal
@@ -1,24 +1,24 @@
--- This file has been generated from package.yaml by hpack version 0.28.2.
+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.33.0.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 4fae1bb408cadb3e1e3086c40f8cba71f6fbb6ec5e2bcca32546e72f83ff2be8
+-- hash: 8825c813c87f8d5631c4ffba6dee7400ac940078993ed71f67f0c86aa14a9ba7
 
 name:           genvalidity-time
-version:        0.2.1.1
+version:        0.2.1.2
 synopsis:       GenValidity support for time
 description:    Please see README.md
 category:       Testing
 homepage:       https://github.com/NorfairKing/validity#readme
 bug-reports:    https://github.com/NorfairKing/validity/issues
 author:         Tom Sydney Kerckhove
-maintainer:     syd.kerckhove@gmail.com,
-                nick.van.den.broeck666@gmail.com
-copyright:      Copyright: (c) 2017-2018 Tom Sydney Kerckhove
+maintainer:     syd@cs-syd.eu
+copyright:      Copyright: (c) 2017-2020 Tom Sydney Kerckhove
 license:        MIT
 license-file:   LICENSE
 build-type:     Simple
-cabal-version:  >= 1.10
 
 source-repository head
   type: git
@@ -51,9 +51,9 @@
       Paths_genvalidity_time
   hs-source-dirs:
       test
-  ghc-options: -threaded -rtsopts -with-rtsopts=-N -Wall -fno-warn-name-shadowing
+  ghc-options: -threaded -rtsopts -with-rtsopts=-N -Wall
   build-depends:
-      base
+      base >=4.7 && <5
     , genvalidity-hspec
     , genvalidity-time
     , hspec
diff --git a/src/Data/GenValidity/Time/Calendar.hs b/src/Data/GenValidity/Time/Calendar.hs
--- a/src/Data/GenValidity/Time/Calendar.hs
+++ b/src/Data/GenValidity/Time/Calendar.hs
@@ -9,9 +9,11 @@
 #if !MIN_VERSION_base(4,8,0)
 import Data.Functor ((<$>))
 #endif
+import Test.QuickCheck
+
 instance GenUnchecked Day where
-    genUnchecked = ModifiedJulianDay <$> genUnchecked
-    shrinkUnchecked _ = []
+  genUnchecked = ModifiedJulianDay <$> genUnchecked
+  shrinkUnchecked _ = []
 
 instance GenValid Day where
-    genValid = ModifiedJulianDay <$> genValid
+  genValid = (ModifiedJulianDay <$> genValid) `suchThat` isValid
diff --git a/test/Data/GenValidity/TimeSpec.hs b/test/Data/GenValidity/TimeSpec.hs
--- a/test/Data/GenValidity/TimeSpec.hs
+++ b/test/Data/GenValidity/TimeSpec.hs
@@ -1,8 +1,8 @@
 {-# LANGUAGE TypeApplications #-}
 
 module Data.GenValidity.TimeSpec
-    ( spec
-    ) where
+  ( spec
+  ) where
 
 import Test.Hspec
 import Test.Validity
@@ -12,22 +12,13 @@
 
 spec :: Spec
 spec = do
-    genValidSpec @Day
-    shrinkValidSpec @Day
-    genValidSpec @UniversalTime
-    shrinkValidSpec @UniversalTime
-    genValidSpec @DiffTime
-    shrinkValidSpec @DiffTime
-    genValiditySpec @UTCTime
-    shrinkValiditySpec @UTCTime
-    genValidSpec @NominalDiffTime
-    shrinkValidSpec @NominalDiffTime
-    genValidSpec @TimeZone
-    shrinkValidSpec @TimeZone
-    genValiditySpec @TimeOfDay
-    shrinkValiditySpec @TimeOfDay
-    genValiditySpec @LocalTime
-    shrinkValiditySpec @LocalTime
-    genValiditySpec @ZonedTime
-    genValidSpec @TimeLocale
-    shrinkValidSpec @TimeLocale
+  genValidSpec @Day
+  genValidSpec @UniversalTime
+  genValidSpec @DiffTime
+  genValiditySpec @UTCTime
+  genValidSpec @NominalDiffTime
+  genValidSpec @TimeZone
+  genValiditySpec @TimeOfDay
+  genValiditySpec @LocalTime
+  genValiditySpec @ZonedTime
+  genValidSpec @TimeLocale