BUG: read_csv with custom date parser and na_filter=True results in ValueError

pandas/tests/io/test_common.py

@@ -139,6 +139,22 @@ def test_iterator(self):
             tm.assert_frame_equal(first, expected.iloc[[0]])
             tm.assert_frame_equal(pd.concat(it), expected.iloc[1:])
 
+    def test_read_csv_with_custom_date_parser(self):
+        # GH36111
+        def __custom_date_parser(time):
+            time_temp = time.astype(np.float).astype(np.int) # convert float seconds to int type
+            return pd.to_timedelta(time_temp, unit='s')
+
+        testdata = StringIO("""time    e   n   h
+        41047.00	-98573.7297	871458.0640	389.0089
+        41048.00	-98573.7299	871458.0640	389.0089
+        41049.00	-98573.7300	871458.0642	389.0088
+        41050.00	-98573.7299	871458.0643	389.0088
+        41051.00	-98573.7302	871458.0640	389.0086
+            """)
+
+        df = pd.read_csv(testdata, delim_whitespace=True, parse_dates=True, date_parser=__custom_date_parser, index_col='time')
+
     @pytest.mark.parametrize(
         "reader, module, error_class, fn_ext",
         [