Glossary

Recurrence rule (RRULE)

The iCalendar pattern that expands one event definition into a repeating series.

An RRULE describes repetition: every Wednesday, the first Monday of the month, weekly until a date. Apps expand the rule into occurrences, so a season of practices can travel as one compact definition.

Real-world schedules complicate rules with exceptions: skipped holidays (EXDATE) and modified single occurrences. Tools that import feeds must expand rules and honor exceptions, or the calendar quietly gains events that were cancelled.