diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index 863880e222b5d..2c422b4c551b6 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -1,13 +1,13 @@
 """
 Base and utility classes for tseries type pandas objects.
 """
-from datetime import datetime, tzinfo
-from typing import TYPE_CHECKING, Any, List, Optional, TypeVar, Union, cast
+from datetime import datetime
+from typing import TYPE_CHECKING, Any, List, Optional, Tuple, TypeVar, Union, cast
 
 import numpy as np
 
 from pandas._libs import NaT, Timedelta, iNaT, join as libjoin, lib
-from pandas._libs.tslibs import BaseOffset, Resolution, Tick, timezones
+from pandas._libs.tslibs import BaseOffset, Resolution, Tick
 from pandas._typing import Callable, Label
 from pandas.compat.numpy import function as nv
 from pandas.errors import AbstractMethodError
@@ -672,8 +672,6 @@ class DatetimeTimedeltaMixin(DatetimeIndexOpsMixin, Int64Index):
     but not PeriodIndex
     """
 
-    tz: Optional[tzinfo]
-
     # Compat for frequency inference, see GH#23789
     _is_monotonic_increasing = Index.is_monotonic_increasing
     _is_monotonic_decreasing = Index.is_monotonic_decreasing
@@ -931,22 +929,9 @@ def join(
             sort=sort,
         )
 
-    def _maybe_utc_convert(self, other):
-        this = self
-        if not hasattr(self, "tz"):
-            return this, other
-
-        if isinstance(other, type(self)):
-            if self.tz is not None:
-                if other.tz is None:
-                    raise TypeError("Cannot join tz-naive with tz-aware DatetimeIndex")
-            elif other.tz is not None:
-                raise TypeError("Cannot join tz-naive with tz-aware DatetimeIndex")
-
-            if not timezones.tz_compare(self.tz, other.tz):
-                this = self.tz_convert("UTC")
-                other = other.tz_convert("UTC")
-        return this, other
+    def _maybe_utc_convert(self: _T, other: Index) -> Tuple[_T, Index]:
+        # Overridden by DatetimeIndex
+        return self, other
 
     # --------------------------------------------------------------------
     # List-Like Methods
diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 11417e0b3317e..ce6f2cbdf5eaa 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -1,12 +1,18 @@
 from datetime import date, datetime, time, timedelta, tzinfo
 import operator
-from typing import TYPE_CHECKING, Optional
+from typing import TYPE_CHECKING, Optional, Tuple
 import warnings
 
 import numpy as np
 
 from pandas._libs import NaT, Period, Timestamp, index as libindex, lib
-from pandas._libs.tslibs import Resolution, ints_to_pydatetime, parsing, to_offset
+from pandas._libs.tslibs import (
+    Resolution,
+    ints_to_pydatetime,
+    parsing,
+    timezones,
+    to_offset,
+)
 from pandas._libs.tslibs.offsets import prefix_mapping
 from pandas._typing import DtypeObj, Label
 from pandas.errors import InvalidIndexError
@@ -411,6 +417,21 @@ def union_many(self, others):
             return this.rename(res_name)
         return this
 
+    def _maybe_utc_convert(self, other: Index) -> Tuple["DatetimeIndex", Index]:
+        this = self
+
+        if isinstance(other, DatetimeIndex):
+            if self.tz is not None:
+                if other.tz is None:
+                    raise TypeError("Cannot join tz-naive with tz-aware DatetimeIndex")
+            elif other.tz is not None:
+                raise TypeError("Cannot join tz-naive with tz-aware DatetimeIndex")
+
+            if not timezones.tz_compare(self.tz, other.tz):
+                this = self.tz_convert("UTC")
+                other = other.tz_convert("UTC")
+        return this, other
+
     # --------------------------------------------------------------------
 
     def _get_time_micros(self):
diff --git a/pandas/io/parsers.py b/pandas/io/parsers.py
index 20c0297448494..2110a2d400be8 100644
--- a/pandas/io/parsers.py
+++ b/pandas/io/parsers.py
@@ -2177,7 +2177,7 @@ def TextParser(*args, **kwds):
     return TextFileReader(*args, **kwds)
 
 
-def count_empty_vals(vals):
+def count_empty_vals(vals) -> int:
     return sum(1 for v in vals if v == "" or v is None)