CI: avoid `guess_datetime_format` failure on 29th of Feburary
- [ ] closes #57672 (Replace xxxx with the GitHub issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Looks reasonable.  I guess it would be a PITA to write a test? > Looks reasonable. I guess it would be a PITA to write a test?

given that the function calls `datetime.now` from Cython - yes, probably Looks good. Could you double check this typing issue? https://github.com/pandas-dev/pandas/actions/runs/8108693644/job/22162385490?pr=57674 thanks - that one should be addressed in https://github.com/pandas-dev/pandas/pull/57689 Thanks @MarcoGorelli 