BUG: Fix+test timezone-preservation in DTA.repeat (#24483)

Also add whatsnew for gh-24265

Author: jbrockmendel

doc/source/whatsnew/v0.24.0.rst

@@ -1367,6 +1367,7 @@ Datetimelike
 - Bug in :attr:`Series.dt` where the cache would not update properly after an in-place operation (:issue:`24408`)
 - Bug in :class:`PeriodIndex` where comparisons against an array-like object with length 1 failed to raise ``ValueError`` (:issue:`23078`)
 - Bug in :meth:`DatetimeIndex.astype`, :meth:`PeriodIndex.astype` and :meth:`TimedeltaIndex.astype` ignoring the sign of the ``dtype`` for unsigned integer dtypes (:issue:`24405`).
+- Fixed bug in :meth:`Series.max` with ``datetime64[ns]``-dtype failing to return ``NaT`` when nulls are present and ``skipna=False`` is passed (:issue:`24265`)
 
 Timedelta
 ^^^^^^^^^

pandas/core/arrays/datetimelike.py

@@ -699,7 +699,7 @@ def repeat(self, repeats, *args, **kwargs):
         """
         nv.validate_repeat(args, kwargs)
         values = self._data.repeat(repeats)
-        return type(self)(values, dtype=self.dtype)
+        return type(self)(values.view('i8'), dtype=self.dtype)
 
     # ------------------------------------------------------------------
     # Null Handling

pandas/tests/arrays/test_datetimes.py

@@ -113,6 +113,16 @@ def test_setitem_clears_freq(self):
         a[0] = pd.Timestamp("2000", tz="US/Central")
         assert a.freq is None
 
+    def test_repeat_preserves_tz(self):
+        dti = pd.date_range('2000', periods=2, freq='D', tz='US/Central')
+        arr = DatetimeArray(dti)
+
+        repeated = arr.repeat([1, 1])
+
+        # preserves tz and values, but not freq
+        expected = DatetimeArray(arr.asi8, freq=None, tz=arr.tz)
+        tm.assert_equal(repeated, expected)
+
 
 class TestSequenceToDT64NS(object):