Paradox or Riddle. Brain-training exercises.

It's not fun talking to you, Lord Mortulus. Okay, you can't handle numbers... Here's a puzzle to rack your brains with. It's one of the most controversial ones. The condemned man was thrown into prison on Saturday with the following words: "You will be hanged at noon on one of the seven days of the next week," the judge said, "but you will not know which day until the morning of the execution." The judge always kept his word. The condemned man was delighted, as he realized that the sentence could not be carried out. The prisoner reasoned as follows: the next Saturday is the last day of the week when the execution is possible, and on Friday afternoon I will already know that I will be hanged on Saturday. This contradicts the judge's words. Therefore, they cannot hang me on Saturday. Consequently, Friday remains the last day when they can hang me. However, they cannot hang me on Friday either, because after Thursday there would be two days left: Friday and Saturday. Since Saturday cannot be the day of execution, they must hang me only on Friday. But if I find out about this on Thursday, the judge's word will be broken. Therefore, Friday is also ruled out. Thursday is also ruled out, because if I survive until Wednesday, I will understand that the execution will take place on Thursday. In the same way, we exclude Wednesday, Tuesday, Monday, and Sunday. He was warned and hanged on one of the days. Where is the error in his reasoning?