From 3e567001355f96aabcb2053f74b047aa3a926d3f Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Mon, 4 Nov 2024 20:58:29 +0800
Subject: [PATCH 01/13] Convert output type in Excel for PeriodIndex in Index
 or MultiIndex be timestamps

---
 pandas/io/formats/excel.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pandas/io/formats/excel.py b/pandas/io/formats/excel.py
index 52b5755558900..ba77746471ecb 100644
--- a/pandas/io/formats/excel.py
+++ b/pandas/io/formats/excel.py
@@ -826,6 +826,9 @@ def _format_hierarchical_rows(self) -> Iterable[ExcelCell]:
                         fill_value=levels._na_value,
                     )
 
+                    if isinstance(values, PeriodIndex):
+                        values = values.to_timestamp()
+
                     for i, span_val in spans.items():
                         mergestart, mergeend = None, None
                         if span_val > 1:
@@ -849,6 +852,10 @@ def _format_hierarchical_rows(self) -> Iterable[ExcelCell]:
                 # Format hierarchical rows with non-merged values.
                 for indexcolvals in zip(*self.df.index):
                     for idx, indexcolval in enumerate(indexcolvals):
+
+                        if isinstance(indexcolval, Period):
+                            indexcolval = indexcolval.to_timestamp()
+
                         yield CssExcelCell(
                             row=self.rowcounter + idx,
                             col=gcolidx,

From 71ef0aa50564345799a347fc24f33c7466d8d2cd Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Fri, 8 Nov 2024 20:22:25 +0800
Subject: [PATCH 02/13] add tests and references

---
 pandas/io/formats/excel.py               |  7 +++--
 pandas/tests/io/formats/test_to_excel.py | 39 ++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/pandas/io/formats/excel.py b/pandas/io/formats/excel.py
index ba77746471ecb..e123de91d4770 100644
--- a/pandas/io/formats/excel.py
+++ b/pandas/io/formats/excel.py
@@ -37,6 +37,7 @@
     DataFrame,
     Index,
     MultiIndex,
+    Period,
     PeriodIndex,
 )
 import pandas.core.common as com
@@ -825,8 +826,8 @@ def _format_hierarchical_rows(self) -> Iterable[ExcelCell]:
                         allow_fill=levels._can_hold_na,
                         fill_value=levels._na_value,
                     )
-
-                    if isinstance(values, PeriodIndex):
+                    # GH#60099
+                    if isinstance(values[0], Period):
                         values = values.to_timestamp()
 
                     for i, span_val in spans.items():
@@ -852,7 +853,7 @@ def _format_hierarchical_rows(self) -> Iterable[ExcelCell]:
                 # Format hierarchical rows with non-merged values.
                 for indexcolvals in zip(*self.df.index):
                     for idx, indexcolval in enumerate(indexcolvals):
-
+                        # GH#60099
                         if isinstance(indexcolval, Period):
                             indexcolval = indexcolval.to_timestamp()
 
diff --git a/pandas/tests/io/formats/test_to_excel.py b/pandas/tests/io/formats/test_to_excel.py
index b40201b9ba1e6..b3b7cd2093b82 100644
--- a/pandas/tests/io/formats/test_to_excel.py
+++ b/pandas/tests/io/formats/test_to_excel.py
@@ -9,6 +9,13 @@
 
 from pandas.errors import CSSWarning
 
+from pandas import (
+    DataFrame,
+    MultiIndex,
+    Timestamp,
+    period_range,
+    to_datetime,
+)
 import pandas._testing as tm
 
 from pandas.io.formats.excel import (
@@ -428,3 +435,35 @@ def test_css_excel_cell_cache(styles, cache_hits, cache_misses):
 
     assert cache_info.hits == cache_hits
     assert cache_info.misses == cache_misses
+
+
+def test_format_hierarchical_rows_with_periodindex():
+    # GH#60099
+    period_index = period_range(start="2006-10-06", end="2006-10-07", freq="D")
+    df = DataFrame({"A": [0, 0]}, index=period_index)
+    converter = CSSToExcelConverter()
+    cells: list[CssExcelCell] = list(converter._format_hierarchical_rows(df))
+    for cell in cells:
+        assert isinstance(cell.val, Timestamp), "Expected cell value to be a Timestamp"
+        assert cell.val in to_datetime(
+            ["2006-10-06", "2006-10-07"]
+        ), "Unexpected cell value"
+
+
+def test_format_hierarchical_rows_with_period():
+    # GH#60099
+    period_index = period_range(start="2006-10-06", end="2006-10-07", freq="D")
+    number_index = ["1", "2"]
+    df = DataFrame(
+        {"A": [0, 0]}, index=MultiIndex.from_arrays([period_index, number_index])
+    )
+    converter = CSSToExcelConverter()
+    cells: list[CssExcelCell] = list(converter._format_hierarchical_rows(df))
+    for cell in cells:
+        if cell.css_col == 0:
+            assert isinstance(
+                cell.val, Timestamp
+            ), "Expected cell value to be a Timestamp"
+            assert cell.val in to_datetime(
+                ["2006-10-06", "2006-10-07"]
+            ), "Unexpected cell value"

From be86dd03ab55fda5db697510e3ce86c72f00bee7 Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Sat, 9 Nov 2024 17:05:34 +0800
Subject: [PATCH 03/13] Modify the tests

---
 pandas/tests/io/excel/test_style.py      | 39 ++++++++++++++++++++++++
 pandas/tests/io/formats/test_to_excel.py | 39 ------------------------
 2 files changed, 39 insertions(+), 39 deletions(-)

diff --git a/pandas/tests/io/excel/test_style.py b/pandas/tests/io/excel/test_style.py
index f70e65e34c584..0adc4b6c7d3f6 100644
--- a/pandas/tests/io/excel/test_style.py
+++ b/pandas/tests/io/excel/test_style.py
@@ -9,6 +9,9 @@
 
 from pandas import (
     DataFrame,
+    MultiIndex,
+    Period,
+    period_range,
     read_excel,
 )
 import pandas._testing as tm
@@ -333,3 +336,39 @@ def test_styler_to_s3(s3_public_bucket, s3so):
             f"s3://{mock_bucket_name}/{target_file}", index_col=0, storage_options=s3so
         )
         tm.assert_frame_equal(result, df)
+
+
+def test_format_hierarchical_rows_periodindex_merge_cells():
+    # GH#60099
+    df = DataFrame(
+        {"A": [1, 2]},
+        index=MultiIndex.from_arrays(
+            [period_range("2023-01", "2023-02", freq="M"), ["X", "Y"]],
+            names=["date", "category"],
+        ),
+    )
+    formatter = ExcelFormatter(df, merge_cells=True)
+    formatted_cells = list(formatter._format_hierarchical_rows())
+
+    for cell in formatted_cells:
+        assert not isinstance(
+            cell.val, Period
+        ), "Period should be converted to Timestamp"
+
+
+def test_format_hierarchical_rows_periodindex_no_merge_cells():
+    # GH#60099
+    df = DataFrame(
+        {"A": [1, 2]},
+        index=MultiIndex.from_arrays(
+            [period_range("2023-01", "2023-02", freq="M"), ["X", "Y"]],
+            names=["date", "category"],
+        ),
+    )
+    formatter = ExcelFormatter(df, merge_cells=False)
+    formatted_cells = list(formatter._format_hierarchical_rows())
+
+    for cell in formatted_cells:
+        assert not isinstance(
+            cell.val, Period
+        ), "Period should be converted to Timestamp"
diff --git a/pandas/tests/io/formats/test_to_excel.py b/pandas/tests/io/formats/test_to_excel.py
index b3b7cd2093b82..b40201b9ba1e6 100644
--- a/pandas/tests/io/formats/test_to_excel.py
+++ b/pandas/tests/io/formats/test_to_excel.py
@@ -9,13 +9,6 @@
 
 from pandas.errors import CSSWarning
 
-from pandas import (
-    DataFrame,
-    MultiIndex,
-    Timestamp,
-    period_range,
-    to_datetime,
-)
 import pandas._testing as tm
 
 from pandas.io.formats.excel import (
@@ -435,35 +428,3 @@ def test_css_excel_cell_cache(styles, cache_hits, cache_misses):
 
     assert cache_info.hits == cache_hits
     assert cache_info.misses == cache_misses
-
-
-def test_format_hierarchical_rows_with_periodindex():
-    # GH#60099
-    period_index = period_range(start="2006-10-06", end="2006-10-07", freq="D")
-    df = DataFrame({"A": [0, 0]}, index=period_index)
-    converter = CSSToExcelConverter()
-    cells: list[CssExcelCell] = list(converter._format_hierarchical_rows(df))
-    for cell in cells:
-        assert isinstance(cell.val, Timestamp), "Expected cell value to be a Timestamp"
-        assert cell.val in to_datetime(
-            ["2006-10-06", "2006-10-07"]
-        ), "Unexpected cell value"
-
-
-def test_format_hierarchical_rows_with_period():
-    # GH#60099
-    period_index = period_range(start="2006-10-06", end="2006-10-07", freq="D")
-    number_index = ["1", "2"]
-    df = DataFrame(
-        {"A": [0, 0]}, index=MultiIndex.from_arrays([period_index, number_index])
-    )
-    converter = CSSToExcelConverter()
-    cells: list[CssExcelCell] = list(converter._format_hierarchical_rows(df))
-    for cell in cells:
-        if cell.css_col == 0:
-            assert isinstance(
-                cell.val, Timestamp
-            ), "Expected cell value to be a Timestamp"
-            assert cell.val in to_datetime(
-                ["2006-10-06", "2006-10-07"]
-            ), "Unexpected cell value"

From a7db60222d73b58ad4d892762d00a3657ef7da43 Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Mon, 11 Nov 2024 14:45:54 +0800
Subject: [PATCH 04/13] Merge and add the tests

---
 pandas/tests/io/excel/test_style.py   | 23 +++--------------------
 pandas/tests/io/excel/test_writers.py | 22 ++++++++++++++++++++++
 2 files changed, 25 insertions(+), 20 deletions(-)

diff --git a/pandas/tests/io/excel/test_style.py b/pandas/tests/io/excel/test_style.py
index 0adc4b6c7d3f6..8bded070ea68b 100644
--- a/pandas/tests/io/excel/test_style.py
+++ b/pandas/tests/io/excel/test_style.py
@@ -338,7 +338,8 @@ def test_styler_to_s3(s3_public_bucket, s3so):
         tm.assert_frame_equal(result, df)
 
 
-def test_format_hierarchical_rows_periodindex_merge_cells():
+@pytest.mark.parametrize("merge_cells", [True, False])
+def test_format_hierarchical_rows_periodindex(merge_cells):
     # GH#60099
     df = DataFrame(
         {"A": [1, 2]},
@@ -347,25 +348,7 @@ def test_format_hierarchical_rows_periodindex_merge_cells():
             names=["date", "category"],
         ),
     )
-    formatter = ExcelFormatter(df, merge_cells=True)
-    formatted_cells = list(formatter._format_hierarchical_rows())
-
-    for cell in formatted_cells:
-        assert not isinstance(
-            cell.val, Period
-        ), "Period should be converted to Timestamp"
-
-
-def test_format_hierarchical_rows_periodindex_no_merge_cells():
-    # GH#60099
-    df = DataFrame(
-        {"A": [1, 2]},
-        index=MultiIndex.from_arrays(
-            [period_range("2023-01", "2023-02", freq="M"), ["X", "Y"]],
-            names=["date", "category"],
-        ),
-    )
-    formatter = ExcelFormatter(df, merge_cells=False)
+    formatter = ExcelFormatter(df, merge_cells=merge_cells)
     formatted_cells = list(formatter._format_hierarchical_rows())
 
     for cell in formatted_cells:
diff --git a/pandas/tests/io/excel/test_writers.py b/pandas/tests/io/excel/test_writers.py
index 81aa0be24bffc..095f2283c8c14 100644
--- a/pandas/tests/io/excel/test_writers.py
+++ b/pandas/tests/io/excel/test_writers.py
@@ -25,6 +25,7 @@
     MultiIndex,
     date_range,
     option_context,
+    period_range,
 )
 import pandas._testing as tm
 
@@ -1549,3 +1550,24 @@ def test_subclass_attr(klass):
     attrs_base = {name for name in dir(ExcelWriter) if not name.startswith("_")}
     attrs_klass = {name for name in dir(klass) if not name.startswith("_")}
     assert not attrs_base.symmetric_difference(attrs_klass)
+
+
+@pytest.mark.parametrize("merge_cells", [True, False])
+def test_excel_round_trip_with_periodindex(merge_cells):
+    # GH#60099
+    df = DataFrame(
+        {"A": [1, 2]},
+        index=MultiIndex.from_arrays(
+            [period_range("2023-01", "2023-02", freq="M"), ["X", "Y"]],
+            names=["date", "category"],
+        ),
+    )
+
+    with BytesIO() as buffer:
+        with ExcelWriter(buffer, engine="xlsxwriter") as writer:
+            df.to_excel(writer, merge_cells=merge_cells)
+
+        buffer.seek(0)
+        result_df = pd.read_excel(buffer, index_col=[0, 1])
+
+    tm.assert_frame_equal(df, result_df)

From 901f69fa92c8fea3053c2d448eb7261085379904 Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Mon, 11 Nov 2024 15:39:18 +0800
Subject: [PATCH 05/13] Merge and add the tests

---
 pandas/tests/io/excel/test_writers.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/pandas/tests/io/excel/test_writers.py b/pandas/tests/io/excel/test_writers.py
index 095f2283c8c14..101733094c7ab 100644
--- a/pandas/tests/io/excel/test_writers.py
+++ b/pandas/tests/io/excel/test_writers.py
@@ -1569,5 +1569,8 @@ def test_excel_round_trip_with_periodindex(merge_cells):
 
         buffer.seek(0)
         result_df = pd.read_excel(buffer, index_col=[0, 1])
+        result_df.index = result_df.index.set_levels(
+            [result_df.index.levels[0].to_period("M"), result_df.index.levels[1]]
+        )
 
     tm.assert_frame_equal(df, result_df)

From 9636523415f34e9e0d35d0be2648204edb1a8fbe Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Mon, 11 Nov 2024 19:31:08 +0800
Subject: [PATCH 06/13] Change excel engine

---
 pandas/tests/io/excel/test_writers.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pandas/tests/io/excel/test_writers.py b/pandas/tests/io/excel/test_writers.py
index 101733094c7ab..5ebaeef8d3bb8 100644
--- a/pandas/tests/io/excel/test_writers.py
+++ b/pandas/tests/io/excel/test_writers.py
@@ -1553,7 +1553,8 @@ def test_subclass_attr(klass):
 
 
 @pytest.mark.parametrize("merge_cells", [True, False])
-def test_excel_round_trip_with_periodindex(merge_cells):
+@pytest.mark.parametrize("engine", ["openpyxl", "xlsxwriter"])
+def test_excel_round_trip_with_periodindex(merge_cells, engine):
     # GH#60099
     df = DataFrame(
         {"A": [1, 2]},
@@ -1564,7 +1565,7 @@ def test_excel_round_trip_with_periodindex(merge_cells):
     )
 
     with BytesIO() as buffer:
-        with ExcelWriter(buffer, engine="xlsxwriter") as writer:
+        with ExcelWriter(buffer, engine=engine) as writer:
             df.to_excel(writer, merge_cells=merge_cells)
 
         buffer.seek(0)

From 7cfd85781e50e7ca25b7fec8d1c876a52b1fc9cc Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Tue, 12 Nov 2024 00:37:22 +0800
Subject: [PATCH 07/13] Delete engine

---
 pandas/tests/io/excel/test_writers.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pandas/tests/io/excel/test_writers.py b/pandas/tests/io/excel/test_writers.py
index 5ebaeef8d3bb8..41553fb02d988 100644
--- a/pandas/tests/io/excel/test_writers.py
+++ b/pandas/tests/io/excel/test_writers.py
@@ -1553,7 +1553,6 @@ def test_subclass_attr(klass):
 
 
 @pytest.mark.parametrize("merge_cells", [True, False])
-@pytest.mark.parametrize("engine", ["openpyxl", "xlsxwriter"])
 def test_excel_round_trip_with_periodindex(merge_cells, engine):
     # GH#60099
     df = DataFrame(
@@ -1565,7 +1564,7 @@ def test_excel_round_trip_with_periodindex(merge_cells, engine):
     )
 
     with BytesIO() as buffer:
-        with ExcelWriter(buffer, engine=engine) as writer:
+        with ExcelWriter(buffer) as writer:
             df.to_excel(writer, merge_cells=merge_cells)
 
         buffer.seek(0)

From 469b6e4b61b9ebcd05cbbe3c372008238446ed25 Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Tue, 12 Nov 2024 10:56:17 +0800
Subject: [PATCH 08/13] Modify the tests

---
 pandas/tests/io/excel/test_style.py   |  5 ++-
 pandas/tests/io/excel/test_writers.py | 54 +++++++++++++++------------
 2 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/pandas/tests/io/excel/test_style.py b/pandas/tests/io/excel/test_style.py
index 8bded070ea68b..8bfbd8761ab4a 100644
--- a/pandas/tests/io/excel/test_style.py
+++ b/pandas/tests/io/excel/test_style.py
@@ -344,7 +344,10 @@ def test_format_hierarchical_rows_periodindex(merge_cells):
     df = DataFrame(
         {"A": [1, 2]},
         index=MultiIndex.from_arrays(
-            [period_range("2023-01", "2023-02", freq="M"), ["X", "Y"]],
+            [
+                period_range(start="2006-10-06", end="2006-10-07", freq="D"),
+                ["X", "Y"],
+            ],
             names=["date", "category"],
         ),
     )
diff --git a/pandas/tests/io/excel/test_writers.py b/pandas/tests/io/excel/test_writers.py
index 41553fb02d988..4ad7bc1445375 100644
--- a/pandas/tests/io/excel/test_writers.py
+++ b/pandas/tests/io/excel/test_writers.py
@@ -338,6 +338,36 @@ def test_multiindex_interval_datetimes(self, tmp_excel):
         )
         tm.assert_frame_equal(result, expected)
 
+    @pytest.mark.parametrize("merge_cells", [True, False])
+    def test_excel_round_trip_with_periodindex(self, tmp_excel, merge_cells):
+        # GH#60099
+        df = DataFrame(
+            {"A": [1, 2]},
+            index=MultiIndex.from_arrays(
+                [
+                    period_range(start="2006-10-06", end="2006-10-07", freq="D"),
+                    ["X", "Y"],
+                ],
+                names=["date", "category"],
+            ),
+        )
+        df.to_excel(tmp_excel, merge_cells=merge_cells)
+        result = pd.read_excel(tmp_excel, index_col=[0, 1])
+        expected = DataFrame(
+            {"A": [1, 2]},
+            MultiIndex.from_arrays(
+                [
+                    [
+                        "2006-10-06 00:00:00",
+                        "2020-01-31 00:00:00",
+                    ],
+                    ["X", "Y"],
+                ],
+                names=["date", "category"],
+            ),
+        )
+        tm.assert_frame_equal(result, expected)
+
 
 @pytest.mark.parametrize(
     "engine,ext",
@@ -1550,27 +1580,3 @@ def test_subclass_attr(klass):
     attrs_base = {name for name in dir(ExcelWriter) if not name.startswith("_")}
     attrs_klass = {name for name in dir(klass) if not name.startswith("_")}
     assert not attrs_base.symmetric_difference(attrs_klass)
-
-
-@pytest.mark.parametrize("merge_cells", [True, False])
-def test_excel_round_trip_with_periodindex(merge_cells, engine):
-    # GH#60099
-    df = DataFrame(
-        {"A": [1, 2]},
-        index=MultiIndex.from_arrays(
-            [period_range("2023-01", "2023-02", freq="M"), ["X", "Y"]],
-            names=["date", "category"],
-        ),
-    )
-
-    with BytesIO() as buffer:
-        with ExcelWriter(buffer) as writer:
-            df.to_excel(writer, merge_cells=merge_cells)
-
-        buffer.seek(0)
-        result_df = pd.read_excel(buffer, index_col=[0, 1])
-        result_df.index = result_df.index.set_levels(
-            [result_df.index.levels[0].to_period("M"), result_df.index.levels[1]]
-        )
-
-    tm.assert_frame_equal(df, result_df)

From 1b284d4ea506ec8178d92836b30d217fd86b839e Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Tue, 12 Nov 2024 14:16:41 +0800
Subject: [PATCH 09/13] unit conversions

---
 pandas/tests/io/excel/test_writers.py | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/pandas/tests/io/excel/test_writers.py b/pandas/tests/io/excel/test_writers.py
index 4ad7bc1445375..cb0610fb68569 100644
--- a/pandas/tests/io/excel/test_writers.py
+++ b/pandas/tests/io/excel/test_writers.py
@@ -352,20 +352,30 @@ def test_excel_round_trip_with_periodindex(self, tmp_excel, merge_cells):
             ),
         )
         df.to_excel(tmp_excel, merge_cells=merge_cells)
+
         result = pd.read_excel(tmp_excel, index_col=[0, 1])
+        if result.index.levels[0].dtype == "datetime64[us]":
+            result.index = result.index.set_levels(
+                result.index.levels[0].astype("datetime64[s]"), level=0
+            )
+
         expected = DataFrame(
             {"A": [1, 2]},
             MultiIndex.from_arrays(
                 [
                     [
-                        "2006-10-06 00:00:00",
-                        "2020-01-31 00:00:00",
+                        pd.to_datetime("2006-10-06 00:00:00"),
+                        pd.to_datetime("2006-10-07 00:00:00"),
                     ],
                     ["X", "Y"],
                 ],
                 names=["date", "category"],
             ),
         )
+        expected.index = expected.index.set_levels(
+            expected.index.levels[0].astype("datetime64[s]"), level=0
+        )
+
         tm.assert_frame_equal(result, expected)
 
 

From 3096671ae1439461581f6dd42589e67018545cac Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Wed, 13 Nov 2024 19:03:45 +0800
Subject: [PATCH 10/13] Modify the 'expected'

---
 pandas/tests/io/excel/test_style.py   |  2 +-
 pandas/tests/io/excel/test_writers.py | 19 +++++++++----------
 2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/pandas/tests/io/excel/test_style.py b/pandas/tests/io/excel/test_style.py
index 8bfbd8761ab4a..45cf240363846 100644
--- a/pandas/tests/io/excel/test_style.py
+++ b/pandas/tests/io/excel/test_style.py
@@ -338,7 +338,7 @@ def test_styler_to_s3(s3_public_bucket, s3so):
         tm.assert_frame_equal(result, df)
 
 
-@pytest.mark.parametrize("merge_cells", [True, False])
+@pytest.mark.parametrize("merge_cells", [True, False, "columns"])
 def test_format_hierarchical_rows_periodindex(merge_cells):
     # GH#60099
     df = DataFrame(
diff --git a/pandas/tests/io/excel/test_writers.py b/pandas/tests/io/excel/test_writers.py
index cb0610fb68569..b9b49bbf1456a 100644
--- a/pandas/tests/io/excel/test_writers.py
+++ b/pandas/tests/io/excel/test_writers.py
@@ -338,7 +338,7 @@ def test_multiindex_interval_datetimes(self, tmp_excel):
         )
         tm.assert_frame_equal(result, expected)
 
-    @pytest.mark.parametrize("merge_cells", [True, False])
+    @pytest.mark.parametrize("merge_cells", [True, False, "columns"])
     def test_excel_round_trip_with_periodindex(self, tmp_excel, merge_cells):
         # GH#60099
         df = DataFrame(
@@ -352,13 +352,7 @@ def test_excel_round_trip_with_periodindex(self, tmp_excel, merge_cells):
             ),
         )
         df.to_excel(tmp_excel, merge_cells=merge_cells)
-
         result = pd.read_excel(tmp_excel, index_col=[0, 1])
-        if result.index.levels[0].dtype == "datetime64[us]":
-            result.index = result.index.set_levels(
-                result.index.levels[0].astype("datetime64[s]"), level=0
-            )
-
         expected = DataFrame(
             {"A": [1, 2]},
             MultiIndex.from_arrays(
@@ -372,9 +366,14 @@ def test_excel_round_trip_with_periodindex(self, tmp_excel, merge_cells):
                 names=["date", "category"],
             ),
         )
-        expected.index = expected.index.set_levels(
-            expected.index.levels[0].astype("datetime64[s]"), level=0
-        )
+        if tmp_excel.endswith(".ods"):
+            expected.index = expected.index.set_levels(
+                expected.index.levels[0].astype("datetime64[s]"), level=0
+            )
+        else:
+            expected.index = expected.index.set_levels(
+                expected.index.levels[0].astype("datetime64[us]"), level=0
+            )
 
         tm.assert_frame_equal(result, expected)
 

From 704d42a529590beaa848441ae2ce4427807958f3 Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Sun, 17 Nov 2024 17:12:06 +0800
Subject: [PATCH 11/13] save memory and modify format

---
 pandas/tests/io/excel/test_style.py   |  2 +-
 pandas/tests/io/excel/test_writers.py | 14 ++++++--------
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/pandas/tests/io/excel/test_style.py b/pandas/tests/io/excel/test_style.py
index 45cf240363846..8f615cbddf7f8 100644
--- a/pandas/tests/io/excel/test_style.py
+++ b/pandas/tests/io/excel/test_style.py
@@ -352,7 +352,7 @@ def test_format_hierarchical_rows_periodindex(merge_cells):
         ),
     )
     formatter = ExcelFormatter(df, merge_cells=merge_cells)
-    formatted_cells = list(formatter._format_hierarchical_rows())
+    formatted_cells = formatter._format_hierarchical_rows()
 
     for cell in formatted_cells:
         assert not isinstance(
diff --git a/pandas/tests/io/excel/test_writers.py b/pandas/tests/io/excel/test_writers.py
index b9b49bbf1456a..a77c9ce26c8eb 100644
--- a/pandas/tests/io/excel/test_writers.py
+++ b/pandas/tests/io/excel/test_writers.py
@@ -366,14 +366,12 @@ def test_excel_round_trip_with_periodindex(self, tmp_excel, merge_cells):
                 names=["date", "category"],
             ),
         )
-        if tmp_excel.endswith(".ods"):
-            expected.index = expected.index.set_levels(
-                expected.index.levels[0].astype("datetime64[s]"), level=0
-            )
-        else:
-            expected.index = expected.index.set_levels(
-                expected.index.levels[0].astype("datetime64[us]"), level=0
-            )
+        time_format = (
+            "datetime64[s]" if tmp_excel.endswith(".ods") else "datetime64[us]"
+        )
+        expected.index = expected.index.set_levels(
+            expected.index.levels[0].astype(time_format), level=0
+        )
 
         tm.assert_frame_equal(result, expected)
 

From 160c249425b891756635f7dfe579e38ac9045088 Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Mon, 18 Nov 2024 00:41:08 +0800
Subject: [PATCH 12/13] add a note

---
 doc/source/whatsnew/v3.0.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v3.0.0.rst b/doc/source/whatsnew/v3.0.0.rst
index 89bc942cb7250..c2b74f6215a6c 100644
--- a/doc/source/whatsnew/v3.0.0.rst
+++ b/doc/source/whatsnew/v3.0.0.rst
@@ -691,6 +691,7 @@ I/O
 - 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`)

From 192c1b73e158d6aef59e9ae265c7224f21dd7f85 Mon Sep 17 00:00:00 2001
From: ZKaoChi <1953542921@qq.com>
Date: Fri, 22 Nov 2024 16:29:51 +0800
Subject: [PATCH 13/13] assert Timestamp instead

---
 doc/source/whatsnew/v3.0.0.rst      | 2 +-
 pandas/tests/io/excel/test_style.py | 9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/doc/source/whatsnew/v3.0.0.rst b/doc/source/whatsnew/v3.0.0.rst
index 3ab8a24e736d5..7242503d7b181 100644
--- a/doc/source/whatsnew/v3.0.0.rst
+++ b/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`)
diff --git a/pandas/tests/io/excel/test_style.py b/pandas/tests/io/excel/test_style.py
index 8f615cbddf7f8..71ef1201e523f 100644
--- a/pandas/tests/io/excel/test_style.py
+++ b/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"