diff --git a/input/models.py b/input/models.py
index 82587b7..e7cedf7 100755
--- a/input/models.py
+++ b/input/models.py
@@ -387,6 +387,14 @@ class Travel(Extern):
     # use content type model to get the end date for the project foreign key
     project_end_quartal = models.CharField(max_length=15, null=True, blank=True, verbose_name='Quartal Projekt Ende')
 
+    def clean(self):
+        if (self.checkin and self.checkout) and (self.checkout < self.checkin):
+            raise forms.ValidationError({
+                'checkout': [
+                    forms.ValidationError('Das Datum der Abreise muss nach dem Datum der Anreise liegen.'),
+                ],
+            })
+
 
 @receiver(pre_save, sender=Travel, dispatch_uid='get_project_end')
 def get_project_end(sender, instance, **kwargs):