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Code RoomTimezone mismatch in renewal calculation
MediumPrep Room Coding #4001

Timezone mismatch in renewal calculation

Vibe & agenticAlgorithms & data structuresMid–Senior~16 min

An AI assistant generated this Python to compute how many whole days until a subscription renews, given a UTC renewal timestamp string:

It returns sensible numbers in your local dev environment. List the bugs and the inputs that expose them.

Implement
days_until_renewal(renewal_utc: str, now_utc: str) → int
Examples
in["2026-02-05T08:30:00Z","2026-01-31T08:30:00Z"]out5
in["2026-01-31T13:30:00Z","2026-01-31T08:30:00Z"]out0
in["2026-01-31T03:30:00Z","2026-01-31T08:30:00Z"]out0
What a strong answer looks like

Treat the AI’s output as a draft to verify, not an answer to trust. Name the specific flaw and the input that triggers it, say how you’d catch it (tests, edge cases, reading critically), and how you’d re-prompt or decompose to get it right.

0:00 of about 16 min

Vibe & agentic: describe the solution in plain language (or narrate it) and the coach grades your approach.

Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.