diff --git a/src/TDB2.cpp b/src/TDB2.cpp
index 34bbb3e50..a1df16eb4 100644
--- a/src/TDB2.cpp
+++ b/src/TDB2.cpp
@@ -1274,18 +1274,101 @@ void TDB2::merge (const std::string& mergeFile)
 ////////////////////////////////////////////////////////////////////////////////
 void TDB2::revert ()
 {
+  // Extract the details of the last txn, and roll it back.
   std::vector <std::string> u = undo.get_lines ();
+  std::string uuid;
+  std::string when;
+  std::string current;
+  std::string prior;
+  revert_undo (u, uuid, when, current, prior);
+
+  // Display diff and confirm.
+  show_diff (current, prior, when);
+  if (! context.config.getBoolean ("confirmation") ||
+      confirm (STRING_TDB2_UNDO_CONFIRM))
+  {
+    // There are six kinds of change possible.  Determine which one, and act
+    // accordingly.
+    //
+    // Revert: task add
+    // [1] 0 --> p
+    //   - erase from pending
+    //   - if in backlog, erase, else add deletion
+    //
+    // Revert: task modify
+    // [2] p --> p'
+    //   - write prior over current in pending
+    //   - add prior to backlog
+    //
+    // Revert: task done/delete
+    // [3] p --> c
+    //   - add prior to pending
+    //   - erase from completed
+    //   - add prior to backlog
+    //
+    // Revert: task modify
+    // [4] c --> p
+    //   - add prior to completed
+    //   - erase from pending
+    //   - add prior to backlog
+    //
+    // Revert: task modify
+    // [5] c --> c'
+    //   - write prior over current in completed
+    //   - add prior to backlog
+    //
+    // Revert: task log
+    // [6] 0 --> c
+    //   - erase from completed
+    //   - if in backlog, erase, else add deletion
+
+    // Modify other data files accordingly.
+    std::vector <std::string> p = pending.get_lines ();
+    revert_pending (p, uuid, current, prior);
+
+    std::vector <std::string> c = completed.get_lines ();
+    revert_completed (p, c, uuid, current, prior);
+
+    std::vector <std::string> b = backlog.get_lines ();
+    revert_backlog (b, uuid, current, prior);
+
+    // Commit.  If processing makes it this far with no exceptions, then we're
+    // done.
+    File::write (undo._file._data, u);
+    File::write (pending._file._data, p);
+    File::write (completed._file._data, c);
+    File::write (backlog._file._data, b);
+
+/*
+    // Perhaps user hand-edited the data files?
+    // Perhaps the task was in completed.data, which was still in file format 3?
+    std::cout << format (STRING_TDB2_MISSING_TASK, uuid.substr (6, 36))
+              << "\n"
+              << STRING_TDB2_UNDO_IMPOSSIBLE
+              << "\n";
+*/
+  }
+  else
+    std::cout << STRING_CMD_CONFIG_NO_CHANGE << "\n";
+}
+
+////////////////////////////////////////////////////////////////////////////////
+void TDB2::revert_undo (
+  std::vector <std::string>& u,
+  std::string& uuid,
+  std::string& when,
+  std::string& current,
+  std::string& prior)
+{
   if (u.size () < 3)
     throw std::string (STRING_TDB2_NO_UNDO);
 
   // pop last tx
   u.pop_back (); // separator.
 
-  std::string current = u.back ().substr (4);
+  current = u.back ().substr (4);
   u.pop_back ();
 
-  std::string prior;
-  std::string when;
   if (u.back ().substr (0, 5) == "time ")
   {
     when = u.back ().substr (5);
@@ -1300,6 +1383,125 @@ void TDB2::revert ()
     u.pop_back ();
   }
 
+  // Extract identifying uuid.
+  std::string::size_type uuidAtt = current.find ("uuid:\"");
+  if (uuidAtt != std::string::npos)
+    uuid = current.substr (uuidAtt, 43); // 43 = uuid:"..."
+  else
+    throw std::string (STRING_TDB2_MISSING_UUID);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+void TDB2::revert_pending (
+  std::vector <std::string>& p,
+  const std::string& uuid,
+  const std::string& current,
+  const std::string& prior)
+{
+  // is 'current' in pending?
+  std::vector <std::string>::iterator task;
+  for (task = p.begin (); task != p.end (); ++task)
+  {
+    if (task->find (uuid) != std::string::npos)
+    {
+      context.debug ("TDB::revert - task found in pending.data");
+
+      // Either revert if there was a prior state, or remove the task.
+      if (prior != "")
+      {
+        *task = prior;
+        std::cout << STRING_TDB2_REVERTED << "\n";
+      }
+      else
+      {
+        p.erase (task);
+        std::cout << STRING_TDB2_REMOVED << "\n";
+      }
+
+      break;
+    }
+  }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+void TDB2::revert_completed (
+  std::vector <std::string>& p,
+  std::vector <std::string>& c,
+  const std::string& uuid,
+  const std::string& current,
+  const std::string& prior)
+{
+  // is 'current' in completed?
+  std::vector <std::string>::iterator task;
+  for (task = c.begin (); task != c.end (); ++task)
+  {
+    if (task->find (uuid) != std::string::npos)
+    {
+      context.debug ("TDB::revert - task found in completed.data");
+
+      // Either revert if there was a prior state, or remove the task.
+      if (prior != "")
+      {
+        *task = prior;
+        if (task->find ("status:\"pending\"")   != std::string::npos ||
+            task->find ("status:\"waiting\"")   != std::string::npos ||
+            task->find ("status:\"recurring\"") != std::string::npos)
+        {
+          c.erase (task);
+          p.push_back (prior);
+          std::cout << STRING_TDB2_REVERTED << "\n";
+          context.debug ("TDB::revert - task belongs in pending.data");
+        }
+        else
+        {
+          std::cout << STRING_TDB2_REVERTED << "\n";
+          context.debug ("TDB::revert - task belongs in completed.data");
+        }
+      }
+      else
+      {
+        c.erase (task);
+
+        std::cout << STRING_TDB2_REVERTED << "\n";
+        context.debug ("TDB::revert - task removed");
+      }
+
+      std::cout << STRING_TDB2_UNDO_COMPLETE << "\n";
+      break;
+    }
+  }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+void TDB2::revert_backlog (
+  std::vector <std::string>& b,
+  const std::string& uuid,
+  const std::string& current,
+  const std::string& prior)
+{
+  std::vector <std::string>::iterator task;
+  for (task = b.begin (); task != b.end (); ++task)
+  {
+    if (task->find (uuid) != std::string::npos)
+    {
+/*
+      context.debug ("TDB::revert_backlog - task found in backlog.data");
+
+//        // Write prior to backlog.data
+//        Task json_task (prior);
+//        backlog.add_line (json_task.composeJSON () + "\n");
+
+*/
+    }
+  }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+void TDB2::show_diff (
+  const std::string& current,
+  const std::string& prior,
+  const std::string& when)
+{
   Date lastChange (strtol (when.c_str (), NULL, 10));
 
   // Set the colors.
@@ -1512,106 +1714,6 @@ void TDB2::revert ()
               << "\n";
   }
 
-  // Output displayed, now confirm.
-  if (context.config.getBoolean ("confirmation") &&
-      !confirm (STRING_TDB2_UNDO_CONFIRM))
-  {
-    std::cout << STRING_CMD_CONFIG_NO_CHANGE << "\n";
-    return;
-  }
-
-  // Extract identifying uuid.
-  std::string uuid;
-  std::string::size_type uuidAtt = current.find ("uuid:\"");
-  if (uuidAtt != std::string::npos)
-    uuid = current.substr (uuidAtt, 43); // 43 = uuid:"..."
-  else
-    throw std::string (STRING_TDB2_MISSING_UUID);
-
-  // load pending.data
-  std::vector <std::string> p = pending.get_lines ();
-
-  // is 'current' in pending?
-  std::vector <std::string>::iterator task;
-  for (task = p.begin (); task != p.end (); ++task)
-  {
-    if (task->find (uuid) != std::string::npos)
-    {
-      context.debug ("TDB::undo - task found in pending.data");
-
-      // Either revert if there was a prior state, or remove the task.
-      if (prior != "")
-      {
-        *task = prior;
-        std::cout << STRING_TDB2_REVERTED << "\n";
-      }
-      else
-      {
-        p.erase (task);
-        std::cout << STRING_TDB2_REMOVED << "\n";
-      }
-
-      // Rewrite files.
-      File::write (pending._file._data, p);
-      File::write (undo._file._data, u);
-      return;
-    }
-  }
-
-  // load completed.data
-  std::vector <std::string> c = completed.get_lines ();
-
-  // is 'current' in completed?
-  for (task = c.begin (); task != c.end (); ++task)
-  {
-    if (task->find (uuid) != std::string::npos)
-    {
-      context.debug ("TDB::undo - task found in completed.data");
-
-      // Either revert if there was a prior state, or remove the task.
-      if (prior != "")
-      {
-        *task = prior;
-        if (task->find ("status:\"pending\"")   != std::string::npos ||
-            task->find ("status:\"waiting\"")   != std::string::npos ||
-            task->find ("status:\"recurring\"") != std::string::npos)
-        {
-          c.erase (task);
-          p.push_back (prior);
-          File::write (completed._file._data, c);
-          File::write (pending._file._data, p);
-          File::write (undo._file._data, u);
-          std::cout << STRING_TDB2_REVERTED << "\n";
-          context.debug ("TDB::undo - task belongs in pending.data");
-        }
-        else
-        {
-          File::write (completed._file._data, c);
-          File::write (undo._file._data, u);
-          std::cout << STRING_TDB2_REVERTED << "\n";
-          context.debug ("TDB::undo - task belongs in completed.data");
-        }
-      }
-      else
-      {
-        c.erase (task);
-        File::write (completed._file._data, c);
-        File::write (undo._file._data, u);
-        std::cout << STRING_TDB2_REVERTED << "\n";
-        context.debug ("TDB::undo - task removed");
-      }
-
-      std::cout << STRING_TDB2_UNDO_COMPLETE << "\n";
-      return;
-    }
-  }
-
-  // Perhaps user hand-edited the data files?
-  // Perhaps the task was in completed.data, which was still in file format 3?
-  std::cout << format (STRING_TDB2_MISSING_TASK, uuid.substr (6, 36))
-            << "\n"
-            << STRING_TDB2_UNDO_IMPOSSIBLE
-            << "\n";
 }
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/src/TDB2.h b/src/TDB2.h
index 199724828..292417fd0 100644
--- a/src/TDB2.h
+++ b/src/TDB2.h
@@ -127,6 +127,11 @@ public:
 
 private:
   bool verifyUniqueUUID (const std::string&);
+  void show_diff (const std::string&, const std::string&, const std::string&);
+  void revert_undo (std::vector <std::string>&, std::string&, std::string&, std::string&, std::string&);
+  void revert_pending (std::vector <std::string>&, const std::string&, const std::string&, const std::string&);
+  void revert_completed (std::vector <std::string>&, std::vector <std::string>&, const std::string&, const std::string&, const std::string&);
+  void revert_backlog (std::vector <std::string>&, const std::string&, const std::string&, const std::string&);
 
 public:
   TF2 pending;