If these so-called prophets knew what the actual role of a prophet was then they would stop trying to predict the future, especially DATE-SETTING!!!
The role of the prophet is to be a spokesman for God and to give the Word of God and to bring sinners to repentance as well as give comfort and exhortation.
Prophets would warn people what would happen if they failed to repent (Jonah and the "three days" prophecy) but never were they to claim some inside knowledge about something happening on a particular day.
Today people will spend tons of money to travel to some other part of the world just to get personal ministry from a "prophet". What most of these people really want is not a prophet as the Bible describes one, but a medium, witch-doctor, warlock or fortune teller dressed in Christian garb.
9 But there was a certain man, called Simon, which beforetime in the same city used sorcery, and bewitched the people of Samaria, giving out that himself was some great one: 10 To whom they all gave heed, from the least to the greatest, saying, This man is the great power of God. 11 And to him they had regard, because that of long time he had bewitched them with sorceries. (Acts 8:9-11)