Understanding RRule Syntax

RRule, or Recurrence Rule, is another syntax used to specify recurring events. It is defined by several properties:

FREQ= ; INTERVAL= ; UNTIL= ; COUNT= ; BYxxx= ; WKST= ; RDATE= ; EXDATE=

• FREQ: Defines the frequency of the event. Possible values are SECONDLY, MINUTELY, HOURLY, DAILY, WEEKLY, MONTHLY, YEARLY.
• INTERVAL: Defines the interval between each FREQ. For example, FREQ=DAILY;INTERVAL=2 means the event occurs every other day.
• UNTIL: Defines the date-time after which the recurrence rule stops. For example, FREQ=DAILY;UNTIL=20231231T000000Z means the event occurs daily until the end of 2023.
• COUNT: Defines the number of occurrences at which to stop the recurrence. For example, FREQ=DAILY;COUNT=10 means the event occurs daily for 10 days.
• BYxxx: Defines specific instances for the recurrence rule. BYxxx could be one of the following: BYSECOND, BYMINUTE, BYHOUR, BYDAY, BYMONTHDAY, BYYEARDAY, BYWEEKNO, BYMONTH, BYSETPOS.
• WKST: Specifies the day on which the workweek starts. Possible values are MO, TU, WE, TH, FR, SA, SU.
• RDATE: Defines the list of dates to be included within the repeating dates. These dates can be a date-time or just a date.
• EXDATE: Defines the list of dates to be excluded within the repeating dates. These dates can be a date-time.

For example, FREQ=DAILY;BYDAY=MO,TU,WE,TH,FR means the event occurs every weekday.