KITFORMA · EDITORIAL ANSWER
Why can Python not subtract an aware datetime from a naive one?
KitForma editorial guide. A naive datetime has no timezone interpretation, while an aware datetime identifies an offset. Python refuses to guess whether the naive value means local time or UTC.
Step-by-step answer
A naive datetime has no timezone interpretation, while an aware datetime identifies an offset. Python refuses to guess whether the naive value means local time or UTC.
Define the input contract, attach the correct zone only when you know the wall-time meaning, and convert instants with
astimezone. Use datetime.now(timezone.utc) for an aware current UTC time. Test a daylight-saving transition as well as an ordinary date. Simply calling replace(tzinfo=timezone.utc) does not convert local time to UTC; it relabels the same clock reading. Store instants and display time zones as separate concerns.Sources and verification
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