1. What are recurrences and why do we need them?

The word “recurrence” in iCalendar refers to the ability of an event to repeat, i.e. schedule a meeting to occur every Wednesday for the next 3 weeks. This sort of scheduling can be represented in iCalendar using a recurrence rule. The purpose of using the recurrence properties is to have the ability to transmit many related event dates in a single transaction. For example, it is possible to create a recurring meeting that will repeat every day for 5 days in one transaction to the invitee list, instead of sending five transactions (one for each day) to the invitee list. Recurrence properties also offer synchronization from desktop to mobile device, for example, a way to quickly send information about many related event dates in a single transaction.

The receiver expands the rule to display the actual dates during processing.