pd.DataFrame({"a": [1, None, 2]}, index=pd.to_datetime([1,2,3], unit="d")).convert_dtypes().interpolate(method="time")

Traceback (most recent call last):
 File "C:\venv\lib\site-packages\IPython\core\interactiveshell.py", line 3437, in run_code
 exec(code_obj, self.user_global_ns, self.user_ns)
 File "<ipython-input-7-4eba02001155>", line 1, in <module>
 pd.DataFrame({"a": [1, None, 2]}, index=pd.to_datetime([1,2,3], unit="d")).convert_dtypes().interpolate(method="time")
 File "C:\venv\lib\site-packages\pandas\core\generic.py", line 7222, in interpolate
 new_data = obj._mgr.interpolate(
 File "C:\venv\lib\site-packages\pandas\core\internals\managers.py", line 593, in interpolate
 return self.apply("interpolate", **kwargs)
 File "C:\venv\lib\site-packages\pandas\core\internals\managers.py", line 427, in apply
 applied = getattr(b, f)(**kwargs)
 File "C:\venv\lib\site-packages\pandas\core\internals\blocks.py", line 1931, in interpolate
 values=values.fillna(value=fill_value, method=method, limit=limit),
 File "C:\venv\lib\site-packages\pandas\core\arrays\base.py", line 655, in fillna
 value, method = validate_fillna_kwargs(value, method)
 File "C:\venv\lib\site-packages\pandas\util\_validators.py", line 367, in validate_fillna_kwargs
 method = clean_fill_method(method)
 File "C:\venv\lib\site-packages\pandas\core\missing.py", line 82, in clean_fill_method
 raise ValueError(f"Invalid fill method. Expecting {expecting}. Got {method}")
ValueError: Invalid fill method. Expecting pad (ffill) or backfill (bfill). Got time

 a
1970年01月02日 1.0
1970年01月03日 1.5
1970年01月04日 2.0