Fix JSON serialization error in Tabulator with mixed NaT datetime columns

panel/tests/widgets/test_tables.py

@@ -275,6 +275,22 @@ def test_tabulator_none_value(document, comm):
     assert model.columns == []
 
 
+def test_tabulator_mixed_nat_datetime_serializes():
+    from bokeh.core.json_encoder import serialize_json
+    from bokeh.core.serialization import Serializer
+
+    df = pd.DataFrame({"date": [pd.NaT, 12]})
+    df["date"] = pd.to_datetime(df["date"]).dt.date
+
+    table = Tabulator(df)
+    _, data = table._get_data()
+
+    ser = Serializer()
+    payload = ser.encode(data)
+
+    serialize_json(payload)
+
+
 def test_tabulator_update_none_value(document, comm, df_mixed):
     table = Tabulator(value=df_mixed)
 

panel/widgets/tables.py

@@ -714,7 +714,7 @@ def _process_df_and_convert_to_cds(self, df: pd.DataFrame) -> tuple[pd.DataFrame
 
         # Ensure NaT serialization is enabled
         try:
-            Serializer.register(pd.NaT, lambda _, __: None)  # type: ignore
+            Serializer.register(type(pd.NaT), lambda _, __: None)  # type: ignore
         except AssertionError:
             pass