diff --git a/casr-logbook.cabal b/casr-logbook.cabal
--- a/casr-logbook.cabal
+++ b/casr-logbook.cabal
@@ -1,5 +1,5 @@
 name:               casr-logbook
-version:            0.5.3
+version:            0.5.4
 license:            OtherLicense
 license-file:       LICENSE
 author:             Tony Morris <ʇǝu˙sıɹɹoɯʇ@ןןǝʞsɐɥ>
@@ -32,7 +32,7 @@
                     base >= 4.8 && < 5
                     , containers >= 0.4 && < 0.6
                     , lucid >= 2.9 && < 3
-                    , digit >= 0.7 && < 0.8
+                    , digit >= 0.8 && < 0.9
                     , time >= 1.5 && < 2
                     , lucid >= 2.9 && < 3
                     , lens >= 4.1 && < 5
diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,3 +1,7 @@
+0.5.4
+
+* Update `digit` dependency.
+
 0.5.3
 
 * Fix show on digits.
diff --git a/src/Data/Aviation/Casr/Logbook/Types/TimeAmount.hs b/src/Data/Aviation/Casr/Logbook/Types/TimeAmount.hs
--- a/src/Data/Aviation/Casr/Logbook/Types/TimeAmount.hs
+++ b/src/Data/Aviation/Casr/Logbook/Types/TimeAmount.hs
@@ -10,14 +10,10 @@
 , timeAmountBy10
 ) where
 
-import Data.Bool(Bool, bool)
-import Data.Maybe(fromMaybe)
-import Data.Ord((>))
 import Data.Semigroup(Semigroup((<>)))
-import Prelude(Integral, divMod, mod)
-import Control.Lens(makeClassy, (^?), over, _1, ( # ))
+import Control.Lens(makeClassy, ( # ))
 import Data.Eq(Eq)
-import Data.Digit(DecDigit, x0, x1, integralDecimal)
+import Data.Digit(DecDigit, x0, integralDecimal, addDecDigit')
 import Data.Int(Int)
 import Data.Monoid(Monoid(mempty, mappend))
 import Data.Ord(Ord)
@@ -47,7 +43,7 @@
   -> TimeAmount
   -> TimeAmount
 TimeAmount f1 p1 `addtimeamount` TimeAmount f2 p2 =
-  let (h, q) = p1 /+/ p2
+  let (h, q) = p1 `addDecDigit'` p2
   in  TimeAmount (f1 + f2 + integralDecimal # (h :: DecDigit)) q 
 
 timeAmountBy10 ::
@@ -65,29 +61,3 @@
     zerotimeamount
   mappend =
     (<>)
-
----- belongs in digit package
-
-mod10 ::
-  Integral a =>
-  a
-  -> DecDigit
-mod10 n =
-  let r = n `mod` 10
-  in fromMaybe (mod10 r) (r ^? integralDecimal)
-
-addDecDigit ::
-  DecDigit
-  -> DecDigit
-  -> (Bool, DecDigit)
-addDecDigit a b =
-  let (x, r) =
-        (integralDecimal # a + integralDecimal # b) `divMod` 10
-  in  (x > 0, mod10 (r :: Int))
-
-(/+/) ::
-  DecDigit
-  -> DecDigit
-  -> (DecDigit, DecDigit)
-(/+/) a b =
-  over _1 (bool x0 x1) (addDecDigit a b)