Can You Solve The Unexpected Hanging Paradox

 A criminal convicted of murder has been sentenced to hanging but to surprise him the judge has only told him that he will be hanged in the next five days. The criminal is left to ponder when he will be hanged he then realises that they can't hang him on Friday because if they haven't hanged him by Thursday they can only hang him on Friday. Then he realises that if they haven't hanged him by Wednesday they can only hang him on Thursday so they can't hang him on Thursday and so on. When he is hanged on Wednesday his is surprised can you find the flaw in his logic.