diff --git a/beesdoo_shift/models/planning.py b/beesdoo_shift/models/planning.py
index 50d39a1d9..e8a59ede4 100644
--- a/beesdoo_shift/models/planning.py
+++ b/beesdoo_shift/models/planning.py
@@ -214,10 +214,19 @@ def _nb_worker_max(self):
                     )
                 )
 
+    @api.constrains("start_time", "end_time")
+    def _check_real_hour(self):
+        for rec in self:
+            if not (-0.001 < rec.start_time < 24) or not (
+                -0.001 < rec.end_time < 24
+            ):
+                raise UserError(
+                    _("Start time and End time need to be between 0 and 23:59")
+                )
+
     @api.onchange("start_time", "end_time")
     def _get_duration(self):
-        if self.start_time and self.end_time:
-            self.duration = self.end_time - self.start_time
+        self.duration = (self.end_time or 0.0) - (self.start_time or 0.0)
 
     @api.onchange("duration")
     def _set_duration(self):