Xtreme Calendar allows you to add appointments that occur on a monthly basis. There are two ways to add an appointment that occurs on a single day of the month for multiple months. The first option allows you to specify the exact date of the month, for example, you can specify that an appointment should be scheduled on the 15th day of every 4th month. The second option allows you to specify the day of a week during the month, for example, you can specify that the appointment should be scheduled on the second Monday of every month. This allows you to easily set up an appointment that occurs every month or every couple of months.