Red hasn’t posed one in a while so here goes. Today’s conundrum is also known at the Thursday Hanging Paradox.
A condemned prisoner is told on Sunday that he will be hanged at dawn one morning in the next seven days and that it will come as a complete surprise. At first, understandably depressed, he weeps, but then beings to ponder the situation for a moment. He suddenly realizes that they cannot hang him next Sunday because that is the last of the 7 days and thus it would not be a surprise. He keeps going. If they cannot hang him on Sunday, then they cannot hang him on Saturday because Sunday is out as a possible hanging day and thus, hanging him on Saturday would not be a surprise either. Extending this logic through the week, he concludes that they cannot hang him at all. Of course, he is totally surprised when he is taken out of his cell on Thursday and hanged at dawn.