assert Timestamp instead

Author: ZKaoChi

doc/source/whatsnew/v3.0.0.rst

@@ -688,10 +688,10 @@ I/O
 - Bug in :meth:`DataFrame.from_records` where ``columns`` parameter with numpy structured array was not reordering and filtering out the columns (:issue:`59717`)
 - Bug in :meth:`DataFrame.to_dict` raises unnecessary ``UserWarning`` when columns are not unique and ``orient='tight'``. (:issue:`58281`)
 - Bug in :meth:`DataFrame.to_excel` when writing empty :class:`DataFrame` with :class:`MultiIndex` on both axes (:issue:`57696`)
+- Bug in :meth:`DataFrame.to_excel` where the :class:`MultiIndex` index with a period level was not a date (:issue:`60099`)
 - Bug in :meth:`DataFrame.to_stata` when writing :class:`DataFrame` and ``byteorder=`big```. (:issue:`58969`)
 - Bug in :meth:`DataFrame.to_stata` when writing more than 32,000 value labels. (:issue:`60107`)
 - Bug in :meth:`DataFrame.to_string` that raised ``StopIteration`` with nested DataFrames. (:issue:`16098`)
-- Bug in :meth:`ExcelFormatter._format_hierarchical_rows` where output type in excel for multiIndex with period levels is not a date (:issue:`60099`)
 - Bug in :meth:`HDFStore.get` was failing to save data of dtype datetime64[s] correctly (:issue:`59004`)
 - Bug in :meth:`read_csv` causing segmentation fault when ``encoding_errors`` is not a string. (:issue:`59059`)
 - Bug in :meth:`read_csv` raising ``TypeError`` when ``index_col`` is specified and ``na_values`` is a dict containing the key ``None``. (:issue:`57547`)

pandas/tests/io/excel/test_style.py

@@ -10,7 +10,7 @@
 from pandas import (
     DataFrame,
     MultiIndex,
-    Period,
+    Timestamp,
     period_range,
     read_excel,
 )
@@ -355,6 +355,7 @@ def test_format_hierarchical_rows_periodindex(merge_cells):
     formatted_cells = formatter._format_hierarchical_rows()
 
     for cell in formatted_cells:
-        assert not isinstance(
-            cell.val, Period
-        ), "Period should be converted to Timestamp"
+        if cell.row != 0 and cell.col == 0:
+            assert isinstance(
+                cell.val, Timestamp
+            ), "Period should be converted to Timestamp"