The stdlib datetime module is in more of a sorry state than certain third party libraries and is full of footguns, as you, a read-the-docs-and-changelogs-carefully person, can surely tell from the myriad deprecations and warnings added over the years, not to mention the confusing params like tz and tzinfo. Heavily tested doesn’t mean shit when the semantics of the API is fundamentally flawed and can’t be updated.