From 3e62a86f24a7789492d41af88af9d800cbbff77f Mon Sep 17 00:00:00 2001
From: adam <adam@adam>
Date: Sat, 28 Mar 2020 18:51:03 +0100
Subject: [PATCH 1/3] BUG: ensure consistent behavior of Index.is_all_dates
 (#19204)

---
 doc/source/whatsnew/v1.1.0.rst    |  1 +
 pandas/core/indexes/base.py       |  9 ++++++++-
 pandas/tests/indexes/test_base.py | 10 ++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v1.1.0.rst b/doc/source/whatsnew/v1.1.0.rst
index 6eedf9dee5266..ba2ebfff79ad9 100644
--- a/doc/source/whatsnew/v1.1.0.rst
+++ b/doc/source/whatsnew/v1.1.0.rst
@@ -636,6 +636,7 @@ Indexing
 - Bug in :meth:`Series.__getitem__` allowing missing labels with ``np.ndarray``, :class:`Index`, :class:`Series` indexers but not ``list``, these now all raise ``KeyError`` (:issue:`33646`)
 - Bug in :meth:`DataFrame.truncate` and :meth:`Series.truncate` where index was assumed to be monotone increasing (:issue:`33756`)
 - Indexing with a list of strings representing datetimes failed on :class:`DatetimeIndex` or :class:`PeriodIndex`(:issue:`11278`)
+- Bug in :meth:`Index.is_all_dates` incorrectly returning ``False`` when inferred type of index was other dates than datetime (:issue:`19204`)
 
 Missing
 ^^^^^^^
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 79af28dc5f2ce..8e2c1f6939693 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -1951,7 +1951,14 @@ def is_all_dates(self) -> bool:
         """
         Whether or not the index values only consist of dates.
         """
-        return is_datetime_array(ensure_object(self._values))
+        return self.inferred_type in [
+            "datetime64",
+            "datetime",
+            "date",
+            "timedelta64",
+            "timedelta",
+            "period",
+        ]
 
     # --------------------------------------------------------------------
     # Pickle Methods
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index 9f235dcdbb295..824dfefb8d6bc 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -1160,6 +1160,16 @@ def test_is_object(self, indices, expected):
     def test_is_all_dates(self, indices, expected):
         assert indices.is_all_dates is expected
 
+    @pytest.mark.parametrize(
+        "index",
+        ["datetime", "datetime-tz", "period", "timedelta", "empty"],
+        indirect=["index"],
+    )
+    def test_is_all_dates_consistency(self, index):
+        # GH 19204
+        non_date = pd.Index(["not a date"])
+        assert index.is_all_dates == index.append(non_date)[:-1].is_all_dates
+
     def test_summary(self, indices):
         self._check_method_works(Index._summary, indices)
 

From b3259ad0a3f15dcb150bce32376a63b1169e3e5e Mon Sep 17 00:00:00 2001
From: Adam Blokus <adamblokus@gmail.com>
Date: Sat, 11 Apr 2020 12:26:27 +0200
Subject: [PATCH 2/3] BUG: ensure consistent behavior of Index.is_all_dates
 (#19204) - improved tests, removed unnecessary imports

---
 pandas/core/indexes/base.py       | 3 +--
 pandas/tests/indexes/test_base.py | 8 ++++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 8e2c1f6939693..f98aa55ac7708 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -9,7 +9,7 @@
 
 from pandas._libs import algos as libalgos, index as libindex, lib
 import pandas._libs.join as libjoin
-from pandas._libs.lib import is_datetime_array, no_default
+from pandas._libs.lib import no_default
 from pandas._libs.tslibs import OutOfBoundsDatetime, Timestamp
 from pandas._libs.tslibs.period import IncompatibleFrequency
 from pandas._libs.tslibs.timezones import tz_compare
@@ -25,7 +25,6 @@
 )
 from pandas.core.dtypes.common import (
     ensure_int64,
-    ensure_object,
     ensure_platform_int,
     is_bool,
     is_bool_dtype,
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index 824dfefb8d6bc..a67fed3e21486 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -1152,8 +1152,12 @@ def test_is_object(self, indices, expected):
             ("bool", False),
             ("categorical", False),
             ("int", False),
-            ("datetime", True),
             ("float", False),
+            ("datetime", True),
+            ("datetime-tz", True),
+            ("period", True),
+            ("timedelta", True),
+            ("empty", False),
         ],
         indirect=["indices"],
     )
@@ -1162,7 +1166,7 @@ def test_is_all_dates(self, indices, expected):
 
     @pytest.mark.parametrize(
         "index",
-        ["datetime", "datetime-tz", "period", "timedelta", "empty"],
+        ["datetime", "datetime-tz", "period", "timedelta"],
         indirect=["index"],
     )
     def test_is_all_dates_consistency(self, index):

From 24b1f923ec966fa0f8710be63e8959dad255129f Mon Sep 17 00:00:00 2001
From: Adam Blokus <adamblokus@gmail.com>
Date: Mon, 4 May 2020 14:49:01 +0200
Subject: [PATCH 3/3] BUG: ensure consistent behavior of Index.is_all_dates
 (#19204) - fixed code formatting

---
 pandas/tests/indexes/test_base.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index a67fed3e21486..ae1df002a6bd9 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -1165,9 +1165,7 @@ def test_is_all_dates(self, indices, expected):
         assert indices.is_all_dates is expected
 
     @pytest.mark.parametrize(
-        "index",
-        ["datetime", "datetime-tz", "period", "timedelta"],
-        indirect=["index"],
+        "index", ["datetime", "datetime-tz", "period", "timedelta"], indirect=["index"],
     )
     def test_is_all_dates_consistency(self, index):
         # GH 19204