ENH: Warn when to_datetime falls back to dateutil when dayfirst is passed

Author: Aloqeely

pandas/core/tools/datetimes.py

@@ -135,10 +135,11 @@ def _guess_datetime_format_for_array(arr, dayfirst: bool | None = False) -> str
                 return guessed_format
             # If there are multiple non-null elements, warn about
             # how parsing might not be consistent
-            if tslib.first_non_null(arr[first_non_null + 1 :]) != -1:
+            if dayfirst or tslib.first_non_null(arr[first_non_null + 1 :]) != -1:
                 warnings.warn(
                     "Could not infer format, so each element will be parsed "
-                    "individually, falling back to `dateutil`. To ensure parsing is "
+                    "individually, falling back to `dateutil` which does not take the "
+                    "dayfirst parameter in consideration. To ensure parsing is "
                     "consistent and as-expected, please specify a format.",
                     UserWarning,
                     stacklevel=find_stack_level(),