An event will happen some day of the next n days, but the day must be such that no one can predict the day {prediction paradox}. Event cannot be on last day, because it is last possible day and so predictable. If it cannot be last day, then it cannot be next-to-last day, because that day has in effect become the last day, and so on, until first day, so event cannot happen.
Examination will be some day next week, but no one can know the day {examination paradox}. Exam cannot be on last day of week, because it is last possible day. Because it cannot be last day, it cannot be next-to-last day, because last day is not possible. It cannot be on other days, because it cannot be on next day.
People that are to hang at noon one day of next week cannot predict the day {hangman's paradox}. If seventh day comes and no hanging has happened yet, prediction is possible, so it is clear that they cannot hang on seventh day. Then they cannot hang on sixth day either, and so on, until first day, so no hanging can happen.
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Date Modified: 2022.0225