strftime does not always return the date in the expected format

[jubuehrer]

Bug report

Bug description:

now = datetime.datetime.now().date()
lol = datetime.date(22, 11, 11)

lol.strftime("%Y-%m-%d") # -> '22-11-11' / This is not correct, it should be '0022-11-11'
now.strftime("%Y-%m-%d") # -> '2023-11-07'
lol.strftime("%y-%m-%d") # -> '22-11-11' / Now its correct

When using %Y in the format I would expect that the year in the return value has a length of four digits.
When converting the string back to a date using strptime() with the format %Y-%m-%d it does crash because it expects the string to have four digits.

CPython versions tested on:

3.11

Operating systems tested on:

Linux

[jubuehrer]

Maybe the bug is not in strftime but in strptime because it should interpret the year 22 as 22 instead of throwing the error ValueError: time data '22-11-11' does not match format '%Y-%m-%d'?

[sobolevn]

Docs clearly state that it should be 0022 for %Y:

https://docs.python.org/3/library/datetime.html#strftime-and-strptime-format-codes

And it works correctly for 3.13:

Python 3.13.0a1+ (heads/issue-111495-dirty:340d25676be, Nov  5 2023, 14:21:42) [Clang 15.0.0 (clang-1500.0.40.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> datetime.date(22, 11, 11).strftime("%Y-%m-%d")
'0022-11-11'

and for 3.11.5:

Python 3.11.5 (main, Sep  5 2023, 10:34:31) [Clang 14.0.3 (clang-1403.0.22.14.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> datetime.date(22, 11, 11).strftime("%Y-%m-%d")
'0022-11-11'

[zware]

This is a glibc issue. @sobolevn showed that Darwin (macOS) is unaffected, here's Windows:

Python 3.11.3 (tags/v3.11.3:f3909b8, Apr  4 2023, 23:49:59) [MSC v.1934 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> datetime.datetime(22, 11, 11).strftime('%Y-%m-%d')
'0022-11-11'

FreeBSD:

Python 3.9.18 (main, Oct  3 2023, 01:17:31) 
[Clang 14.0.5 (https://github.com/llvm/llvm-project.git llvmorg-14.0.5-0-gc1238 on freebsd13
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> datetime.datetime(22, 11, 11).strftime('%Y-%m-%d')
'0022-11-11'

musl:

$ docker run -it --rm python:3.11-alpine
Python 3.11.6 (main, Oct 19 2023, 05:43:48) [GCC 12.2.1 20220924] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> datetime.datetime(22, 11, 11).strftime('%Y-%m-%d')
'0022-11-11'

cosmo:

$ ./o/third_party/python/python.com
Python 3.6.14+ (Actually Portable Python) [GCC 11.2.0] on cosmo
Type "help", "copyright", "credits" or "license" for more information.
>>: import datetime
>>: datetime.datetime(22, 11, 11).strftime('%Y-%m-%d')
'0022-11-11'

And finally, glibc:

$ docker run -it --rm python:3.11-slim
Python 3.11.6 (main, Nov  1 2023, 13:45:43) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> datetime.datetime(22, 11, 11).strftime('%Y-%m-%d')
'22-11-11'
>>> datetime.datetime(22, 11, 11).strftime('%4Y-%m-%d')
'0022-11-11'

See also gh-57514, gh-88776, and probably others. Closing as duplicate of gh-57514.