This also causes an issue when using stftime and strptime together on Linux (Ubuntu 20.04.1 LTS).
When encoding a datetime using strftime and decoding with strptime using the same pattern an error is raised if year < 1000.

Example:
>>> pattern = "%Y-%m-%d"
>>> datetime.strptime(
...     datetime(1, 1, 1).strftime(pattern),
...     pattern
... )
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.8/_strptime.py", line 568, in _strptime_datetime
    tt, fraction, gmtoff_fraction = _strptime(data_string, format)
  File "/usr/lib/python3.8/_strptime.py", line 349, in _strptime
    raise ValueError("time data %r does not match format %r" %
ValueError: time data '1-01-01' does not match format '%Y-%m-%d'