diff --git a/models/acc_operation.py b/models/acc_operation.py
index 45f374a1c77ef31413e3884286071d59f44ccfaa..7aaefab940edc40f2712cc06bb3c3abcd72f7ba5 100644
--- a/models/acc_operation.py
+++ b/models/acc_operation.py
@@ -195,7 +195,7 @@ class AccOperation(models.Model):
         """
         # Calculate delta between 2 dates
         delta = (date_end - date_start).days
-        if delta < 1:
+        if delta <= 1:
             step_display_courbe = "hour"
             step = "hour"
             if not scale: