From e90bb56c33edf4f96c872cecb5f3c591576ce2d9 Mon Sep 17 00:00:00 2001
From: Abdulaziz Aloqeely <52792999+Aloqeely@users.noreply.github.com>
Date: Sat, 1 Jun 2024 05:10:37 +0300
Subject: [PATCH] ENH: Warn when to_datetime falls back to dateutil when
 dayfirst is passed

---
 pandas/core/tools/datetimes.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pandas/core/tools/datetimes.py b/pandas/core/tools/datetimes.py
index b01cdb335ec46..eaca0479ab931 100644
--- a/pandas/core/tools/datetimes.py
+++ b/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(),