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Given a booking start, the moment of change, the booking amount and a tiered policy whose deadlines are either elapsed hours before start ('48 hours') or local calendar days at a local time ('18:00 the day before' in the venue's zone, DST-correct), returns the applicable tier, its deadline instants, the penalty in minor units under your stated rounding, and when the next tier begins; checks an asserted penalty. A change exactly at a deadline is still on time. It carries no airline, hotel or marketplace policy: you supply the tiers. Penalties are percent of amount (basis points) or a fixed minor amount, capped at the booking amount; no tax or FX.