diff --git a/lib/helpers/misc.dart b/lib/helpers/misc.dart
index bbee7333..70147e0a 100644
--- a/lib/helpers/misc.dart
+++ b/lib/helpers/misc.dart
@@ -16,6 +16,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+import 'package:flutter/material.dart';
 import 'package:wger/helpers/consts.dart';
 import 'package:wger/models/workouts/repetition_unit.dart';
 import 'package:wger/models/workouts/weight_unit.dart';
@@ -69,3 +70,19 @@ List<DateTime> daysInRange(DateTime first, DateTime last) {
     (index) => DateTime.utc(first.year, first.month, first.day + index),
   );
 }
+
+extension TimeOfDayExtension on TimeOfDay {
+  bool isAfter(TimeOfDay other) {
+    if(toMinutes() > other.toMinutes()) return true;
+    else return false;
+  }
+
+  bool isBefore(TimeOfDay other) {
+    if(toMinutes() < other.toMinutes()) return true;
+    else return false;
+  }
+
+  int toMinutes() {
+    return ((hour*60) + minute);
+  }
+}
\ No newline at end of file
diff --git a/lib/l10n/app_en.arb b/lib/l10n/app_en.arb
index c37c279f..191af707 100644
--- a/lib/l10n/app_en.arb
+++ b/lib/l10n/app_en.arb
@@ -274,6 +274,7 @@
   "@timeEnd": {
     "description": "The end time of a workout"
   },
+  "timeStartAhead": "Start time cannot be ahead of end time",
   "ingredient": "Ingredient",
   "@ingredient": {},
   "energy": "Energy",
diff --git a/lib/widgets/workouts/gym_mode.dart b/lib/widgets/workouts/gym_mode.dart
index 27c8e84b..6999bce7 100644
--- a/lib/widgets/workouts/gym_mode.dart
+++ b/lib/widgets/workouts/gym_mode.dart
@@ -27,6 +27,7 @@ import 'package:wger/helpers/consts.dart';
 import 'package:wger/helpers/gym_mode.dart';
 import 'package:wger/helpers/json.dart';
 import 'package:wger/helpers/ui.dart';
+import 'package:wger/helpers/misc.dart';
 import 'package:wger/models/exercises/exercise.dart';
 import 'package:wger/models/http_exception.dart';
 import 'package:wger/models/workouts/day.dart';
@@ -823,6 +824,14 @@ class _SessionPageState extends State<SessionPage> {
                         onSaved: (newValue) {
                           _session.timeStart = stringToTime(newValue);
                         },
+                        validator: (_) {
+                          TimeOfDay startTime = stringToTime(timeStartController.text);
+                          TimeOfDay endTime = stringToTime(timeEndController.text);
+                          if(startTime.isAfter(endTime)) {
+                            return AppLocalizations.of(context).timeStartAhead;
+                          }
+                          return null;
+                        }
                       ),
                     ),
                     SizedBox(width: 10),
@@ -842,7 +851,7 @@ class _SessionPageState extends State<SessionPage> {
                             initialTime: TimeOfDay.now(),
                           );
 
-                          timeStartController.text = timeToString(pickedTime)!;
+                          timeEndController.text = timeToString(pickedTime)!;
                         },
                         onSaved: (newValue) {
                           _session.timeEnd = stringToTime(newValue);