GH-70647: Deprecate strptime day of month parsing without a year present to avoid leap-year bugs by gpshead · Pull Request #117107 · python/cpython

I would be mildly in favor of deprecating all these ambiguous kinds of formats anyway, though I do think "add a fixed year to the string to be parsed" is an uglier hack than adding some mechanism for explicitly specifying defaults (e.g. accepting a default_datetime: datetime | None parameter, or default_kwargs={...}).

Which I suppose is my way of saying that I generally agree with this — I suspect that any format that has a year and a day-of-month without an actual month is way more likely to be due to an error than not. Preferably we'd give people a more accurate warning in that case, but for now any kind of warning to call attention to the situation should help.