Django has deprecated `django.utils.timezone.utc` in favor of `datetime.timezone.utc`. The rest of the `django.utils.timezone` methods are still supported. Furthermore, `datetime.timezone.utc` cannot be directly imported, and must be accessed through `datetime.timezone`. This leaves two possible importable targets named `datetime` (both `datetime` and `datetime.datetime`) and named `timezone` (`datetime.timezone` and `django.utils.timezone`), all of which are relevant. In an effort to keep things sane and consistent, the codebase now imports the top-level `datetime` (accessing everything as a direct property access of that) and `django.utils.timezone` as `timezone` in all affected modules. We may opt to go this route with all new Django code going forward. With this change, all datetime-related warnings in unit tests have been removed.