`dt.UTC` is a 3.11+ alias, but crdt-sync declares requires-python = ">=3.10"
and the CI matrix tests 3.10 — so `crdt-sync tests` has been failing on the
3.10 leg since before this branch (commit 493db693 failed the same way).
It collected as `AttributeError: module 'datetime' has no attribute 'UTC'`.
This is not only a test problem: `_firebase_auth._utcnow()` is library code,
so on 3.10 every token-expiry check would have raised at runtime. The three
consumers (diet-guard, screen-locker, wake-alarm) all declare >=3.10 too, so
honouring the floor is the right direction rather than raising it.
`dt.UTC is dt.timezone.utc` evaluates to True — the same singleton under two
spellings — so this is a pure rename with no behaviour change.
Verified on a real pyenv 3.10.16 venv, not just the 3.14 dev interpreter:
239 passed.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GZH89WEqAjuJT8WZdqc7AP