If I was served with a criminal summons and the offense date is incorrect by 10 days of the incident is this grounds for dismissal?

A mistake as to the date of the offense could possibly be grounds for dismissal, or could be used as a defense.  The Commonwealth is required to prove Beyond a reasonable doubt that you committed the crime as alleged in the police report and as charged in the court.  If there is a discrepancy as to when the offense actually occured, it will be difficult to prove the offense beyond a reasonable doubt.  Also, it may give you an alabi as to what occurred on the particular date and time charged.

You should contact a local lawyer to review the complaint to see if any motions can be filed prior to the arraignment of the charges.