Caused by #1506(#1505) #1485(#1362)

I believe local timezone is the expected default for naive datetime objects. Breaking those expectations will lead to unnecessary surprises for the users. It will also lead to awkward conversions if another library that does follow this convention is used.

Python's datetime.fromtimestamp and datetime.astimezone assume local timezone for naive objects. There are three warnings in datetime docs that start with "Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC."

Using utc time is surely more sane than using local time, but the better way to do that is timezone aware datetimes, not naive-utc datetimes. For example Message.date should be timezone aware.