diff --git a/lib/actions/timer_actions.dart b/lib/actions/timer_actions.dart
new file mode 100644
index 0000000..5190d9f
--- /dev/null
+++ b/lib/actions/timer_actions.dart
@@ -0,0 +1,9 @@
+import 'package:time_progress_calculator/models/timer.dart';
+
+abstract class Action {}
+
+class UpdateTimerAction extends Action {
+  final Timer updatedTimer;
+
+  UpdateTimerAction(this.updatedTimer);
+}
\ No newline at end of file
diff --git a/lib/reducers/app_state_reducer.dart b/lib/reducers/app_state_reducer.dart
new file mode 100644
index 0000000..1f4673e
--- /dev/null
+++ b/lib/reducers/app_state_reducer.dart
@@ -0,0 +1,7 @@
+import 'package:time_progress_calculator/actions/timer_actions.dart';
+import 'package:time_progress_calculator/models/app_state.dart';
+import 'package:time_progress_calculator/reducers/timer_reducer.dart';
+
+AppState appReducer(AppState state, Action action) {
+  return AppState(timer: timersReducer(state.timer, action));
+}
diff --git a/lib/reducers/timer_reducer.dart b/lib/reducers/timer_reducer.dart
new file mode 100644
index 0000000..4a741a6
--- /dev/null
+++ b/lib/reducers/timer_reducer.dart
@@ -0,0 +1,10 @@
+import 'package:time_progress_calculator/actions/timer_actions.dart';
+import 'package:time_progress_calculator/models/timer.dart';
+import 'package:redux/redux.dart';
+
+final timersReducer = combineReducers<Timer>(
+    [TypedReducer<Timer, UpdateTimerAction>(_updateTimer)]);
+
+Timer _updateTimer(Timer timer, UpdateTimerAction action) {
+  return action.updatedTimer;
+}