What if the officer writes the wrong date on the ticket?

You can try to argue it. He/she may have already caught the error and changed it on the court copies. Depending on the exact nature of the offense ticketed, the police officer has a certain period of time within which to amend the ticket to put in the correct date. Although this type of mistake is not an automatic reason to dismiss the ticket, it might impeach the officer's credibility if it goes to trial. Most likely it would not damage the officer's credibility to the extent where the court will disbelieve everything he/she says about the violation.