How to handle an error on underage drinking ticket?

The general rule is that an incorrect date on a ticket/summons is not a basis to dismiss/invalidate it.  If your daughter is not planning on hiring an attorney, then at the very least she needs to contact the clerk's office at the court where she is scheduled to appear and find out local policy/procedure is when tickets are written out incorrectly.  She will very likely be re-docketed either for the following  Monday, or for some other time.  Your daughter should not simply blow the matter off, due to the fact that doing so could potentially expose her to additional criminal liability.  I suggest that your daughter hire a local attorney to develop a strategy to defend this matter.  Good luck.