How to make a task repeat on the last day of each quarter in Google Calendar?

Question

I've successfully added a repeating event to the last day of every month using the below syntax:

BEGIN:VCALENDAR
BEGIN:VEVENT
DTSTART:20110731
DTEND:20110731
RRULE:FREQ=MONTHLY;BYDAY=SU,MO,TU,WE,TH,FR,SA;BYSETPOS=-1;WKST=SU
SUMMARY:Name of your event
END:VEVENT
END:VCALENDAR 

thanks to the advice of this article (How to make a task repeat on the last day of each month in Google Calendar?) but I need to set up a quarterly repeating event.

Does anyone know how to edit frequency syntax so that the event repeats on the last day of the month every three months (or every x months)?

Answer 1

Just add INTERVAL=3; to the repeating rule (RRULE)

BEGIN:VCALENDAR
BEGIN:VEVENT
DTSTART:20110731
DTEND:20110731
RRULE:FREQ=MONTHLY;INTERVAL=3;BYDAY=SU,MO,TU,WE,TH,FR,SA;BYSETPOS=-1;WKST=SU
SUMMARY:Name of your event
END:VEVENT
END:VCALENDAR