diff --git a/app/Main.hs b/app/Main.hs
index 2f4e709..1c3dee1 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -2,7 +2,7 @@ module Main where
 
 import           Control.Monad
 
-import qualified Brick               as B
+import qualified Brick                   as B
 
 import           TaskMachine.Options
 import           TaskMachine.UI
diff --git a/src/TaskMachine/Task.hs b/src/TaskMachine/Task.hs
index a8a726c..ae82c10 100644
--- a/src/TaskMachine/Task.hs
+++ b/src/TaskMachine/Task.hs
@@ -20,6 +20,8 @@ module TaskMachine.Task
   , charToPriority
   , Description
   , Snippet(..)
+  -- * Misc stuff
+  , compareTasks
   -- * Formatting
   , formatTask
   , formatTasks
@@ -49,6 +51,7 @@ module TaskMachine.Task
   ) where
 
 import           Control.Monad
+import           Data.Function
 import qualified Data.List.NonEmpty   as NE
 import           Data.Void
 
@@ -119,7 +122,7 @@ formatCreated d = 'c' : formatDate d
 data Completion
   = Incomplete
   | Complete (Maybe Day)
-  deriving (Show)
+  deriving (Eq, Ord, Show)
 
 -- | Convert a 'Completion' to its string representation, which can be parsed by 'pCompletion'.
 --
@@ -137,7 +140,7 @@ data Priority
   | PrioH | PrioI | PrioJ | PrioK | PrioL | PrioM | PrioN
   | PrioO | PrioP | PrioQ | PrioR | PrioS | PrioT | PrioU
   | PrioV | PrioW | PrioX | PrioY | PrioZ
-  deriving (Bounded, Enum, Eq, Show, Ord)
+  deriving (Bounded, Enum, Eq, Ord, Show)
 
 -- | Convert a 'Priority' to its string representation, which can be parsed by 'pPriority'.
 --
@@ -178,7 +181,7 @@ data Snippet
   -- ^ A word of the form @key:value@.
   -- The key and value cannot contain any spaces.
   -- The key cannot contain any @":"@ characters, but the value can.
-  deriving (Eq, Show)
+  deriving (Show)
 
 -- | Convert a 'Description' into its string representation, which can be parsed by 'pDescription'.
 --
@@ -226,7 +229,7 @@ pCreated = label "creation date" $ char 'c' *> pDate
 -- | Parse a 'Completion' (see 'formatCompletion').
 pCompletion :: Parser Completion
 pCompletion =   Incomplete <$ char '-'
-            <|> char 'x' *> (label "completion date" $ Complete <$> maybeParse pDate)
+            <|> char 'x' *> label "completion date" (Complete <$> maybeParse pDate)
 
 -- Priority
 
@@ -307,3 +310,22 @@ pTask
 -- | Parse a list of 'Task's (see 'formatTasks').
 pTasks :: Parser [Task]
 pTasks = many pTask <* eof
+
+ {- Misc stuff -}
+
+compareTasks :: Task -> Task -> Ordering
+compareTasks a b = mconcat
+  [ compare (taskCompletion a) (taskCompletion b)
+  , compareMaybe (taskPriority a) (taskPriority b)
+  , compareMaybe (taskDue a) (taskDue b)
+  , compareDescription (taskDescription a) (taskDescription b)
+  ]
+  where
+    -- Inverted compare for Maybes: Nothing comes after Just
+    compareMaybe :: Ord a => Maybe a -> Maybe a -> Ordering
+    compareMaybe Nothing  Nothing  = EQ
+    compareMaybe (Just _) Nothing  = LT
+    compareMaybe Nothing  (Just _) = GT
+    compareMaybe (Just x) (Just y) = compare x y
+    compareDescription :: Description -> Description -> Ordering
+    compareDescription = compare `on` formatDescription
diff --git a/src/TaskMachine/UI.hs b/src/TaskMachine/UI.hs
index b53c74e..c792342 100644
--- a/src/TaskMachine/UI.hs
+++ b/src/TaskMachine/UI.hs
@@ -11,9 +11,9 @@ import qualified Graphics.Vty.Input.Events as VTY
 
 import           TaskMachine.Options
 import           TaskMachine.UI.NewTask
+import           TaskMachine.UI.Popup
 import           TaskMachine.UI.TaskList
 import           TaskMachine.UI.TopBar
-import           TaskMachine.UI.Popup
 import           TaskMachine.UI.Types
 
 drawBaseLayer :: UIState -> B.Widget RName
diff --git a/src/TaskMachine/UI/Task.hs b/src/TaskMachine/UI/Task.hs
index aa1a808..5a2c311 100644
--- a/src/TaskMachine/UI/Task.hs
+++ b/src/TaskMachine/UI/Task.hs
@@ -55,9 +55,9 @@ renderSnippet s                =                                  B.str $ format
 renderTask :: Task -> B.Widget n
 renderTask t = B.hBox $ catMaybes
   [ Just $ withSpace $ renderCompletion $ taskCompletion t
-  , (withSpace . renderPriority) <$> taskPriority t
-  , (withSpace . renderDue) <$> taskDue t
-  , (withSpace . renderCreated) <$> taskCreated t
+  , withSpace . renderPriority <$> taskPriority t
+  , withSpace . renderDue <$> taskDue t
+  , withSpace . renderCreated <$> taskCreated t
   , Just $ renderDescription $ taskDescription t
   ]
 
diff --git a/todo.txt b/todo.txt
index a7ae29b..f37e717 100644
--- a/todo.txt
+++ b/todo.txt
@@ -1,7 +1,7 @@
-- c2018-09-18 Sort tasks by completion, priority, due date, description
-- c2018-09-18 Quit using Esc or q
-- c2018-09-18 Offer "retry" or "quit" +dialogue - syntax error in todo file
 - c2018-09-18 Offer "retry" or "quit" +dialogue - couldn't load from todo file
 - c2018-09-18 Offer "retry" or "quit" +dialogue - couldn't save to todo file
+- c2018-09-18 Offer "retry" or "quit" +dialogue - syntax error in todo file
 - c2018-09-18 Offer to clean up file when loading (adding creation/completion dates)
 - c2018-09-18 Purge - move completed tasks to a separate file
+- c2018-09-18 Quit using Esc or q
+- c2018-09-18 Sort tasks by completion, priority, due date, description