diff --git a/backend/time_tracking/serializers.py b/backend/time_tracking/serializers.py
index 70bcb6b..90b5823 100644
--- a/backend/time_tracking/serializers.py
+++ b/backend/time_tracking/serializers.py
@@ -19,6 +19,8 @@ class TimeEntryCreateSerializer(serializers.ModelSerializer):
     def validate(self, attrs):
         if not attrs.get('start_time') and not attrs.get('end_time'):
             raise serializers.ValidationError('Une heure d’entrée ou de sortie est requise.')
+        if attrs.get('start_time') and attrs.get('end_time') and attrs['end_time'] <= attrs['start_time']:
+            raise serializers.ValidationError('L’heure de sortie doit être après l’heure d’entrée.')
         return attrs
 
 class TimeEntryUpdateSerializer(serializers.ModelSerializer):
@@ -29,6 +31,8 @@ class TimeEntryUpdateSerializer(serializers.ModelSerializer):
     def validate(self, attrs):
         if not attrs.get('start_time') and not attrs.get('end_time'):
             raise serializers.ValidationError('Une heure d’entrée ou de sortie est requise.')
+        if attrs.get('start_time') and attrs.get('end_time') and attrs['end_time'] <= attrs['start_time']:
+            raise serializers.ValidationError('L’heure de sortie doit être après l’heure d’entrée.')
         return attrs
 
 class WeeklySummarySerializer(serializers.Serializer):
diff --git a/backend/time_tracking/views.py b/backend/time_tracking/views.py
index c25383d..ea1e5a9 100644
--- a/backend/time_tracking/views.py
+++ b/backend/time_tracking/views.py
@@ -6,6 +6,7 @@ from django.contrib.auth.models import User
 from django.db import transaction
 from django.utils import timezone
 from datetime import datetime, date, timedelta
+from datetime import time as datetime_time
 from decouple import config
 from .models import TimeEntry
 from .serializers import (
@@ -40,8 +41,8 @@ class TimeEntryScanView(APIView):
         code = str(request.data.get('code') or '').strip().strip('"\'')
         if '=' in code:
             code = code.split('=', 1)[1].strip().strip('"\'')
-        enter_code = config('SECRET_POINTAGE_ENTER', default='').strip()
-        exit_code = config('SECRET_POINTAGE_EXIT', default='').strip()
+        enter_code = config('SECRET_POINTAGE_ENTER', default='').strip().strip('"\'')
+        exit_code = config('SECRET_POINTAGE_EXIT', default='').strip().strip('"\'')
         if code == enter_code:
             action = 'enter'
         elif code == exit_code:
@@ -50,6 +51,16 @@ class TimeEntryScanView(APIView):
             return Response({'error': 'QR code de pointage invalide.'}, status=status.HTTP_400_BAD_REQUEST)
 
         now = timezone.localtime()
+        requested_time = request.data.get('time')
+        if requested_time:
+            try:
+                selected_time = datetime_time.fromisoformat(str(requested_time)[:5])
+            except ValueError:
+                return Response({'error': 'Heure invalide.'}, status=status.HTTP_400_BAD_REQUEST)
+        else:
+            selected_time = now.time().replace(second=0, microsecond=0)
+        resolution = request.data.get('resolution')
+
         with transaction.atomic():
             open_entry = TimeEntry.objects.select_for_update().filter(
                 user=request.user,
@@ -57,20 +68,64 @@ class TimeEntryScanView(APIView):
                 start_time__isnull=False,
                 end_time__isnull=True,
             ).order_by('-start_time').first()
+            open_exit = TimeEntry.objects.select_for_update().filter(
+                user=request.user,
+                date=now.date(),
+                start_time__isnull=True,
+                end_time__isnull=False,
+            ).order_by('-end_time').first()
 
             if action == 'enter':
                 if open_entry:
-                    return Response({'error': 'Une entrée est déjà ouverte pour aujourd’hui.'}, status=status.HTTP_400_BAD_REQUEST)
-                entry = TimeEntry.objects.create(user=request.user, date=now.date(), start_time=now.time())
+                    if resolution == 'cancel_entry':
+                        open_entry.delete()
+                        return Response({'action': action, 'message': 'Entrée annulée.'})
+                    if resolution == 'complete_entry':
+                        if selected_time <= open_entry.start_time:
+                            return Response({'error': 'L’heure de sortie doit être après l’entrée.'}, status=status.HTTP_400_BAD_REQUEST)
+                        open_entry.end_time = selected_time
+                        open_entry.save(update_fields=['end_time', 'updated_at'])
+                        return Response({'action': action, 'message': 'Sortie enregistrée pour l’entrée précédente.', 'entry': TimeEntrySerializer(open_entry).data})
+                    return Response({'error': 'Une entrée est déjà ouverte.', 'conflict': 'open_entry', 'options': ['cancel_entry', 'complete_entry']}, status=status.HTTP_409_CONFLICT)
+                if open_exit:
+                    if resolution == 'cancel_exit':
+                        open_exit.delete()
+                        return Response({'action': action, 'message': 'Sortie annulée.'})
+                    if resolution == 'complete_exit':
+                        open_exit.start_time = selected_time
+                        open_exit.save(update_fields=['start_time', 'updated_at'])
+                        return Response({'action': action, 'message': 'Entrée enregistrée pour la sortie précédente.', 'entry': TimeEntrySerializer(open_exit).data})
+                    return Response({'error': 'Une sortie existe déjà.', 'conflict': 'open_exit', 'options': ['cancel_exit', 'complete_exit']}, status=status.HTTP_409_CONFLICT)
+                entry = TimeEntry.objects.create(user=request.user, date=now.date(), start_time=selected_time)
                 message = 'Entrée enregistrée.'
             elif open_entry:
-                open_entry.end_time = now.time()
+                open_entry.end_time = selected_time
                 open_entry.save(update_fields=['end_time', 'updated_at'])
                 entry = open_entry
                 message = 'Sortie enregistrée.'
+            elif open_exit:
+                if resolution == 'cancel_exit':
+                    open_exit.delete()
+                    return Response({'action': action, 'message': 'Sortie annulée.'})
+                if resolution == 'complete_exit':
+                    if selected_time >= open_exit.end_time:
+                        return Response({'error': 'L’heure d’entrée doit être avant la sortie.'}, status=status.HTTP_400_BAD_REQUEST)
+                    open_exit.start_time = selected_time
+                    open_exit.save(update_fields=['start_time', 'updated_at'])
+                    return Response({'action': action, 'message': 'Entrée enregistrée pour la sortie précédente.', 'entry': TimeEntrySerializer(open_exit).data})
+                return Response({'error': 'Une sortie existe déjà.', 'conflict': 'open_exit', 'options': ['cancel_exit', 'complete_exit']}, status=status.HTTP_409_CONFLICT)
             else:
-                entry = TimeEntry.objects.create(user=request.user, date=now.date(), end_time=now.time())
-                message = 'Sortie enregistrée sans entrée correspondante.'
+                previous_open_entry = TimeEntry.objects.select_for_update().filter(
+                    user=request.user,
+                    start_time__isnull=False,
+                    end_time__isnull=True,
+                ).exclude(date=now.date()).order_by('-date', '-start_time').first()
+                if previous_open_entry:
+                    entry = TimeEntry.objects.create(user=request.user, date=now.date(), end_time=selected_time)
+                    message = 'Sortie enregistrée. L’entrée est restée sur la journée précédente.'
+                else:
+                    entry = TimeEntry.objects.create(user=request.user, date=now.date(), end_time=selected_time)
+                    message = 'Sortie enregistrée sans entrée correspondante.'
 
         return Response({'action': action, 'message': message, 'entry': TimeEntrySerializer(entry).data})
 
diff --git a/frontend/src/api/time.js b/frontend/src/api/time.js
index 206bec3..a77e789 100644
--- a/frontend/src/api/time.js
+++ b/frontend/src/api/time.js
@@ -21,12 +21,15 @@ export const timeApi = {
     }
   },
 
-  scanTimeEntry: async (code) => {
+  scanTimeEntry: async (code, options = {}) => {
     try {
-      const response = await api.post('/time/entries/scan/', { code });
+      const response = await api.post('/time/entries/scan/', { code, ...options });
       return response.data;
     } catch (error) {
-      throw new Error(error.response?.data?.error || `Erreur lors du pointage: ${error.message}`);
+      const scanError = new Error(error.response?.data?.error || `Erreur lors du pointage: ${error.message}`);
+      scanError.conflict = error.response?.data?.conflict;
+      scanError.code = error.response?.status;
+      throw scanError;
     }
   },
 
diff --git a/frontend/src/pages/TimeClockPage.css b/frontend/src/pages/TimeClockPage.css
index 759d96a..5d761bd 100644
--- a/frontend/src/pages/TimeClockPage.css
+++ b/frontend/src/pages/TimeClockPage.css
@@ -163,4 +163,23 @@ th {
   margin-top: 20px;
   padding: 15px;
   background-color: #e9ecef;
+}
+
+.scan-conflict {
+  display: grid;
+  gap: 10px;
+  margin-top: 16px;
+  padding: 16px;
+  background: #fff8ed;
+  border: 1px solid #e7c58b;
+  border-radius: var(--radius-sm);
+}
+
+.scan-conflict p {
+  margin: 0;
+  color: var(--text-muted);
+}
+
+.scan-conflict input {
+  width: 150px;
 }
\ No newline at end of file
diff --git a/frontend/src/pages/TimeClockPage.jsx b/frontend/src/pages/TimeClockPage.jsx
index c638d31..d3d6e95 100644
--- a/frontend/src/pages/TimeClockPage.jsx
+++ b/frontend/src/pages/TimeClockPage.jsx
@@ -13,12 +13,15 @@ const TimeClockPage = () => {
   const [isScanning, setIsScanning] = useState(false);
   const [scanResult, setScanResult] = useState('');
   const [scanMessage, setScanMessage] = useState('');
+  const [scanConflict, setScanConflict] = useState(null);
+  const [conflictTime, setConflictTime] = useState(new Date().toTimeString().slice(0, 5));
   const [error, setError] = useState('');
   const [currentTime, setCurrentTime] = useState(new Date());
   const [timeEntries, setTimeEntries] = useState([]);
   const [loading, setLoading] = useState(true);
   const [newEntry, setNewEntry] = useState({
     date: new Date().toISOString().split('T')[0],
+    end_date: new Date().toISOString().split('T')[0],
     start_time: '',
     end_time: ''
   });
@@ -64,9 +67,21 @@ const TimeClockPage = () => {
     }
 
     try {
-      await timeApi.createTimeEntry(newEntry);
+      if (newEntry.date === newEntry.end_date) {
+        await timeApi.createTimeEntry({
+          date: newEntry.date,
+          start_time: newEntry.start_time,
+          end_time: newEntry.end_time,
+        });
+      } else {
+        await Promise.all([
+          timeApi.createTimeEntry({ date: newEntry.date, start_time: newEntry.start_time }),
+          timeApi.createTimeEntry({ date: newEntry.end_date, end_time: newEntry.end_time }),
+        ]);
+      }
       setNewEntry({
         date: new Date().toISOString().split('T')[0],
+        end_date: new Date().toISOString().split('T')[0],
         start_time: '',
         end_time: ''
       });
@@ -144,6 +159,7 @@ const TimeClockPage = () => {
 
   const handleQrResult = async (code) => {
     setScanResult(code);
+    setScanConflict(null);
     stopScanner();
 
     try {
@@ -151,7 +167,27 @@ const TimeClockPage = () => {
       setScanMessage(response.message);
       await loadTimeEntries();
     } catch (scanError) {
-      setError(scanError.message);
+      if (scanError.code === 409 && scanError.conflict) {
+        setScanConflict({ code, type: scanError.conflict, message: scanError.message });
+      } else {
+        setError(scanError.message);
+      }
+    }
+  };
+
+  const resolveScanConflict = async (resolution) => {
+    if (!scanConflict) return;
+    setError('');
+    try {
+      const response = await timeApi.scanTimeEntry(scanConflict.code, {
+        resolution,
+        time: conflictTime,
+      });
+      setScanMessage(response.message);
+      setScanConflict(null);
+      await loadTimeEntries();
+    } catch (resolutionError) {
+      setError(resolutionError.message);
     }
   };
 
@@ -209,6 +245,7 @@ const TimeClockPage = () => {
     setError('');
     setScanResult('');
     setScanMessage('');
+    setScanConflict(null);
 
     if (!window.isSecureContext && window.location.hostname !== 'localhost' && window.location.hostname !== '127.0.0.1') {
       setError('La caméra nécessite une connexion HTTPS sur cette adresse réseau.');
@@ -272,6 +309,28 @@ const TimeClockPage = () => {
 
       {scanMessage && <div className="alert alert-success">{scanMessage}</div>}
 
+      {scanConflict && (
+        <div className="scan-conflict" role="dialog" aria-live="polite">
+          <strong>{scanConflict.message}</strong>
+          <p>Choisissez quoi faire avec le pointage précédent :</p>
+          <label htmlFor="conflict-time">Heure à utiliser</label>
+          <input
+            id="conflict-time"
+            type="time"
+            value={conflictTime}
+            onChange={(event) => setConflictTime(event.target.value)}
+          />
+          <div className="btn-group">
+            <button type="button" className="btn btn-danger" onClick={() => resolveScanConflict(scanConflict.type === 'open_entry' ? 'cancel_entry' : 'cancel_exit')}>
+              Annuler le pointage
+            </button>
+            <button type="button" className="btn btn-primary" onClick={() => resolveScanConflict(scanConflict.type === 'open_entry' ? 'complete_entry' : 'complete_exit')}>
+              Renseigner l’heure
+            </button>
+          </div>
+        </div>
+      )}
+
       {/* Time tracking section */}
       <div className="time-tracking-section">
         
@@ -329,6 +388,16 @@ const TimeClockPage = () => {
                           required
                         />
                       </div>
+                      <div className="form-group">
+                        <label>Date de sortie:</label>
+                        <input
+                          type="date"
+                          value={newEntry.end_date}
+                          min={newEntry.date}
+                          onChange={(e) => setNewEntry({...newEntry, end_date: e.target.value})}
+                          required
+                        />
+                      </div>
                       <div className="form-group">
                         <label>Heure d'entrée:</label>
                         <input