I came across this puzzle a while ago and recently recalled it but couldn't come up with any solid solution/explanation. What are your thoughts? I want to choose one day, in a five day window (we'll say monday to friday), on which an event will occur. (For simplicity of interpretation and wording we'll say the event will occur within the first hour of the day.) People know the event will occur within the five day window. I don't want anyone to know on the day befor that the event will occur the next day. It would clearly seem, then, that if ,on Thursday, the event hasn't occured people will know that the event will occur on Friday and therefor I shouldn't choose Friday. But if the people know I will not choose Friday, the last day they think I might choose is Thursday. Because of this, if on Wednesday the event hasn't occured, people will know that the event will occur on Thursday and therefor I shouldn't choose Thursday. It would seem this would continue until I decide that I simply can't choose any day on which the event will occur AND no one will know the day befor. What, if anything, is wrong?