`datetime.strptime(dt.strftime("%c"), "%c"))` fails when year is <1000.

Bug report

Bug description:

>>> from datetime import datetime
>>> datetime.strptime(datetime(1000, 1, 1).strftime("%c"), "%c")
datetime.datetime(1000, 1, 1, 0, 0)
>>> datetime.strptime(datetime(999, 1, 1).strftime("%c"), "%c")
Traceback (most recent call last):
  File "<python-input-1>", line 1, in <module>
    datetime.strptime(datetime(999, 1, 1).strftime("%c"), "%c")
    ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/nlx5/Documents/Programming/Python/cpython/Lib/_strptime.py", line 573, in _strptime_datetime
    tt, fraction, gmtoff_fraction = _strptime(data_string, format)
                                    ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/home/nlx5/Documents/Programming/Python/cpython/Lib/_strptime.py", line 352, in _strptime
    raise ValueError("time data %r does not match format %r" %
                     (data_string, format))
ValueError: time data 'Tue Jan  1 00:00:00 999' does not match format '%c'

Discovered this when adding some hypothesis tests for strptime/strftime. I doubt this is a real problem anyone is going to have in the real world, but maybe.

I do not know if this is locale-specific or OS specific.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-124778

从 issue 中的 datetime.strptime/strftime 复现开始，检查 Lib/_strptime.py，尤其是 %c 的解析路径。检查年份小于 1000 时以及所报告的 Linux 环境中的行为；当 year-999 往返成功且不破坏现有解析行为时，即表示完成。