Bug report

Bug description:

If you over-specify a datetime strptime string, it seems thatdatetime.strptime when encountering a component that has been specified twice, will overwrite earlier values with more recent ones.

>>>datetime.strptime("200099","%Y%y")datetime.datetime(1999,1,1,0,0)

One approach would be to ban over-specified formats, but that would be a problem for someone who wants to, use a format like "%M %B" (e.g. something sortable by month number while also showing month name), so I think we don't want to do that.

Alternatively we could start raising an exception if you getdifferent values from these two things, or possibly a warning.

Or we can just accept that if you use a weird format you should expect weird behavior.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• GH-124549: Add a note that when over-specifying datetime format, only the last directive gets used. #125009
• gh-124549: Warn on conflicting directives indatetime.*.strptime #132524