BUG: chokes on pd.DatetimeTZDtype if there are no rows.

This is a follow up to pandas-dev#41875

Author: pcorpet

doc/source/whatsnew/v3.0.0.rst

@@ -594,6 +594,7 @@ Reshaping
 ^^^^^^^^^
 - Bug in :meth:`DataFrame.join` inconsistently setting result index name (:issue:`55815`)
 - Bug in :meth:`DataFrame.unstack` producing incorrect results when ``sort=False`` (:issue:`54987`, :issue:`55516`)
+- Bug in :meth:`DataFrame.unstack` producing incorrect results when manipulating empty DataFrame using dtype extensions (:issue:`59123`)
 
 Sparse
 ^^^^^^

pandas/core/reshape/reshape.py

@@ -291,7 +291,12 @@ def get_new_values(self, values, fill_value=None):
         # if our mask is all True, then we can use our existing dtype
         if mask_all:
             dtype = values.dtype
-            new_values = np.empty(result_shape, dtype=dtype)
+            if isinstance(dtype, ExtensionDtype):
+                # GH#41875
+                cls = dtype.construct_array_type()
+                new_values = cls._empty(result_shape, dtype=dtype)
+            else:
+                new_values = np.empty(result_shape, dtype=dtype)
         else:
             if isinstance(dtype, ExtensionDtype):
                 # GH#41875

pandas/tests/reshape/test_pivot.py

@@ -2769,3 +2769,18 @@ def test_unstack_copy(self, m):
         result = df.unstack(sort=False)
         result.iloc[0, 0] = -1
         tm.assert_frame_equal(df, df_orig)
+
+    @pytest.mark.parametrize("tz", [None, "UTC"])
+    def test_pivot_empty_with_datetime(self, tz):
+        # GH#59126
+        df = DataFrame(
+            {
+                "timestamp": [pd.Timestamp("2024-01-01T00:00", tz=tz)],
+                "category": ["A"],
+                "value": [100],
+            }
+        )
+        df_pivoted = df[df.category == "C"].pivot_table(
+            index="category", columns="value", values="timestamp"
+        )
+        assert df_pivoted.empty