For the classes of problems that you mention, I consider them as separate data types entirely and they shouldn’t ever touch your timezone-aware date-times objec

For the classes of problems that you mention, I consider them as separate data types entirely and they shouldn’t ever touch your timezone-aware date-times objects. They should be stored as a composite types of your date, maybe time, and target timezone. If you can mix timezone-aware objects with non-timezone aware objects like you do in Python, it’s get pretty dangerous because people will just mix them willy nilly and add and subtract the timezone-aware parts and then you get some really subtle date/time bugs. That’s why I believe either a date-time MUST have a timezone and for other cases, you need a specialty data type for your domain, possibly provided by your date/time library.