PATCH /api/v1/photos/{id} returned 500 with
'can't subtract offset-naive and offset-aware datetimes' when the
frontend sent a tz-aware taken_at value (e.g. 2026-05-09T00:12+02:00).
The photos.taken_at column is timestamp without time zone, so asyncpg
refuses to bind a tz-aware datetime.
The frontend's datetime-local input is supposed to be naive but real-
world locales / browsers / paste flows occasionally include offsets.
Normalize on the server: if tzinfo is present, convert to UTC and drop
the tzinfo so both shapes round-trip cleanly.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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