If you have an appointment that takes place regularly, you can define its recurrence by clicking the Recurrence button in the Appointment Editor or by clicking OptionsRecurrence. You can then choose a time and date when the appointment stops recurring, and, under Exceptions, pick individual days when the appointment does not recur. Make your selections from left to right, and you form a sentence: "Every two weeks on Monday and Friday until January 3, 2015" or "Every month on the first Friday for 12 occurrences."