In [2]: to_datetime('20 Monday', format='%V %A') --------------------------------------------------------------------------- ValueError Traceback (most recent call last) Cell In[2], line 1 ----> 1 to_datetime('20 Monday', format='%V %A') File ~/pandas-dev/pandas/core/tools/datetimes.py:1100, in to_datetime(arg, errors, dayfirst, yearfirst, utc, format, exact, unit, infer_datetime_format, origin, cache) 1098 result = convert_listlike(argc, format) 1099 else: -> 1100 result = convert_listlike(np.array([arg]), format)[0] 1101 if isinstance(arg, bool) and isinstance(result, np.bool_): 1102 result = bool(result) # TODO: avoid this kludge. File ~/pandas-dev/pandas/core/tools/datetimes.py:442, in _convert_listlike_datetimes(arg, format, name, utc, unit, errors, dayfirst, yearfirst, exact) 439 require_iso8601 = format is not None and format_is_iso(format) 441 if format is not None and not require_iso8601: --> 442 return _to_datetime_with_format( 443 arg, 444 orig_arg, 445 name, 446 utc, 447 format, 448 exact, 449 errors, 450 ) 452 result, tz_parsed = objects_to_datetime64ns( 453 arg, 454 dayfirst=dayfirst, (...) 461 exact=exact, 462 ) 464 if tz_parsed is not None: 465 # We can take a shortcut since the datetime64 numpy array 466 # is in UTC File ~/pandas-dev/pandas/core/tools/datetimes.py:543, in _to_datetime_with_format(arg, orig_arg, name, utc, fmt, exact, errors) 540 return _box_as_indexlike(result, utc=utc, name=name) 542 # fallback --> 543 res = _array_strptime_with_fallback(arg, name, utc, fmt, exact, errors) 544 return res File ~/pandas-dev/pandas/core/tools/datetimes.py:485, in _array_strptime_with_fallback(arg, name, utc, fmt, exact, errors) 481 """  482 Call array_strptime, with fallback behavior depending on 'errors'.  483 """ 484 try: --> 485 result, timezones = array_strptime( 486 arg, fmt, exact=exact, errors=errors, utc=utc 487 ) 488 except OutOfBoundsDatetime: 489 if errors == "raise": File ~/pandas-dev/pandas/_libs/tslibs/strptime.pyx:347, in pandas._libs.tslibs.strptime.array_strptime() 345 week_of_year = int(found_dict[group_key]) 346 if group_key == "U": --> 347 # U starts week on Sunday. 348 week_of_year_start = 6 349 else: ValueError: ISO week directive '%V' is incompatible with the year directive '%Y'. Use the ISO year '%G' instead.