diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+# 1.9.5
+
+- Support `time-1.11.1`
+  - Add `NFData CalandarDiffDays` instance
+
 # 1.9.4
 
 - Support `time-1.11`
diff --git a/src/Data/Time/Calendar/Compat.hs b/src/Data/Time/Calendar/Compat.hs
--- a/src/Data/Time/Calendar/Compat.hs
+++ b/src/Data/Time/Calendar/Compat.hs
@@ -52,10 +52,10 @@
 import System.Locale (TimeLocale (..))
 #endif
 
-import Data.Data      (Data, Typeable)
-import Data.Monoid    (Monoid (..))
-import Data.Semigroup (Semigroup (..))
-
+import Control.DeepSeq (NFData (..))
+import Data.Data       (Data, Typeable)
+import Data.Monoid     (Monoid (..))
+import Data.Semigroup  (Semigroup (..))
 
 -------------------------------------------------------------------------------
 -- CalendarDiffTime
@@ -91,6 +91,9 @@
 
 instance Show CalendarDiffDays where
     show (CalendarDiffDays m d) = "P" ++ show m ++ "M" ++ show d ++ "D"
+
+instance NFData CalendarDiffDays where
+    rnf (CalendarDiffDays x y) = rnf x `seq` rnf y
 
 calendarDay :: CalendarDiffDays
 calendarDay = CalendarDiffDays 0 1
diff --git a/src/Data/Time/Orphans.hs b/src/Data/Time/Orphans.hs
--- a/src/Data/Time/Orphans.hs
+++ b/src/Data/Time/Orphans.hs
@@ -99,16 +99,15 @@
 deriving instance Data SystemTime
 #endif
 
--- TODO: add an upper bound when it's known
-#if MIN_VERSION_time(1,9,0)
+#if MIN_VERSION_time(1,9,0) && !MIN_VERSION_time(1,11,1)
 instance NFData DayOfWeek where
     rnf !_ = ()
-#endif
 
--- TODO: add an upper bound when it's known
-#if MIN_VERSION_time(1,9,0)
 instance NFData CalendarDiffTime where
     rnf (CalendarDiffTime x y) = rnf x `seq` rnf y
+
+instance NFData CalendarDiffDays where
+    rnf (CalendarDiffDays x y) = rnf x `seq` rnf y
 #endif
 
 #if !MIN_VERSION_time(1,11,0)
@@ -127,8 +126,7 @@
 
 #endif
 
--- TODO: add an upper bound when it's known
-#if MIN_VERSION_time(1,11,0)
+#if MIN_VERSION_time(1,11,0) && !MIN_VERSION_time(1,11,1)
 instance NFData Month where
     rnf (MkMonth m) = rnf m
 
diff --git a/test-instances/Test.hs b/test-instances/Test.hs
--- a/test-instances/Test.hs
+++ b/test-instances/Test.hs
@@ -79,6 +79,7 @@
     , test (undefined :: UTCTime)
     , test (undefined :: UniversalTime)
     , test (undefined :: CalendarDiffTime)
+    , test (undefined :: CalendarDiffDays)
     , test (undefined :: TimeZone)
     , test (undefined :: TimeOfDay)
     , test (undefined :: LocalTime)
diff --git a/time-compat.cabal b/time-compat.cabal
--- a/time-compat.cabal
+++ b/time-compat.cabal
@@ -1,6 +1,6 @@
 cabal-version:      1.12
 name:               time-compat
-version:            1.9.4
+version:            1.9.5
 synopsis:           Compatibility package for time
 description:
   This packages tries to compat as much of @time@ features as possible.
@@ -57,7 +57,7 @@
       base          >=4.3     && <4.15
     , base-orphans  >=0.8.1   && <0.9
     , deepseq       >=1.3.0.0 && <1.4 || >=1.4.1.1 && <1.5
-    , time          >=1.2     && <1.3 || >=1.4 && <1.7 || >=1.8 && <1.9 || >=1.9.2 && <1.9.4 || >=1.10 && <1.10.1 || >=1.11 && <1.11.1
+    , time          >=1.2     && <1.3 || >=1.4 && <1.7 || >=1.8 && <1.9 || >=1.9.2 && <1.9.4 || >=1.10 && <1.10.1 || >=1.11 && <1.11.2
 
   if flag(old-locale)
     build-depends:
@@ -141,7 +141,7 @@
     , deepseq
     , QuickCheck        >=2.13   && <2.15
     , tagged            >=0.8.6  && <0.9
-    , tasty             >=1.2.1  && <1.4
+    , tasty             >=1.2.1  && <1.5
     , tasty-hunit       >=0.10   && <0.11
     , tasty-quickcheck  >=0.10   && <0.11
     , time-compat