TST: Concatenating categorical datetime columns (pandas-dev#53949)

Added unit-test

Author: rsm-23

pandas/tests/reshape/concat/test_categorical.py

@@ -1,3 +1,5 @@
+from datetime import datetime
+
 import numpy as np
 
 from pandas.core.dtypes.dtypes import CategoricalDtype
@@ -166,6 +168,22 @@ def test_concat_categorical_tz(self):
         )
         tm.assert_series_equal(result, expected)
 
+    def test_concat_categorical_datetime(self):
+        # GH-39443
+        df1 = DataFrame(
+            {"x": Series(datetime(2021, 1, 1), index=[0], dtype="category")}
+        )
+        df2 = DataFrame(
+            {"x": Series(datetime(2021, 1, 2), index=[1], dtype="category")}
+        )
+
+        result = pd.concat([df1, df2])
+        expected = DataFrame(
+            {"x": Series([datetime(2021, 1, 1), datetime(2021, 1, 2)])}
+        )
+
+        tm.assert_equal(result, expected)
+
     def test_concat_categorical_unchanged(self):
         # GH-12007
         # test fix for when concat on categorical and float