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/src/Data/Validity/Time/Calendar.hs b/src/Data/Validity/Time/Calendar.hs
--- a/src/Data/Validity/Time/Calendar.hs
+++ b/src/Data/Validity/Time/Calendar.hs
@@ -8,4 +8,12 @@
 
 -- | Valid according to the 'Integer' it contains.
 instance Validity Day where
-    validate = delve "toModifiedJulianDay" . toModifiedJulianDay
+  validate d@(ModifiedJulianDay i) =
+    mconcat
+      [ delve "toModifiedJulianDay" i
+      , declare "The day happened after the beginning of time" $
+        d > beginningOfTime
+      ]
+
+beginningOfTime :: Day
+beginningOfTime = ModifiedJulianDay $ -((138 * (10 ^ (8 :: Integer))) * 356)
diff --git a/validity-time.cabal b/validity-time.cabal
--- a/validity-time.cabal
+++ b/validity-time.cabal
@@ -1,22 +1,20 @@
-cabal-version: >= 1.10
+cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.29.6.
+-- This file has been generated from package.yaml by hpack version 0.33.0.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 7f8a3e8969f86465118727b47c793d1a274d2211198f45f8442e93edbd36184d
+-- hash: 34bf1aa8675c937c93958e6500cd23b70561bd03efbe8689b9efe948bbb97257
 
 name:           validity-time
-version:        0.2.0.2
+version:        0.2.0.3
 synopsis:       Validity instances for time
-description:    Please see README.md
 category:       Validity
 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