diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,7 @@
+0.0.7
+
+* Add `diffDates`
+
 0.0.6
 
 * Fix bug in `realAmount`
diff --git a/national-australia-bank.cabal b/national-australia-bank.cabal
--- a/national-australia-bank.cabal
+++ b/national-australia-bank.cabal
@@ -1,5 +1,5 @@
 name:                 national-australia-bank
-version:              0.0.6
+version:              0.0.7
 synopsis:             Functions for National Australia Bank transactions
 description:          Parsing, Processing and other functions for National Australia Bank transactions
 license:              BSD3
diff --git a/src/Data/Bank/NationalAustraliaBank/NationalAustraliaBank.hs b/src/Data/Bank/NationalAustraliaBank/NationalAustraliaBank.hs
--- a/src/Data/Bank/NationalAustraliaBank/NationalAustraliaBank.hs
+++ b/src/Data/Bank/NationalAustraliaBank/NationalAustraliaBank.hs
@@ -39,7 +39,7 @@
 import qualified Data.Sv.Decode as D
 import qualified Data.Sv.Encode as E
 import Data.Validation ( toEither )
-import Data.Time ( fromGregorian, toGregorian, Day )
+import Data.Time ( fromGregorian, toGregorian, diffDays, Day )
 import Data.Functor.Contravariant ( Contravariant(contramap) )
 import Data.Ratio ( Ratio, (%) )
 import System.Directory
@@ -372,6 +372,13 @@
       mon Dec = 12
       dt = integralDecimal # d1 * 10 + integralDecimal # d2
   in  fromGregorian year (mon m) dt
+
+diffDates ::
+  Date
+  -> Date
+  -> Integer
+diffDates dt1 dt2 =
+  dateDay dt1 `diffDays` dateDay dt2
 
 data Amount =
   Amount {