use RRULE INTERVAL instead of EXDATE

Currently the ICS export uses EXDATE for biweekly tutorials/lectures, which is less compliant to the iCalendar spec of setting the RRULE to FREQ:WEEKLY;INTERVAL:2;COUNT=7. I’m not sure how ICS exports works underneath as of yet, but this seems simpler.

[jethrokuan]

I thought about that, in particular the fact that the timetable events don’t really change makes it a viable solution. That would certainly solve my issue, but I don’t think it’s a much better solution than EXDATE for the general public.

[ngzhian]

@jethrokuan another way is that you can return 2 events that make up this, 1 pre recess week, 1 post recess week. But there are problems with this as well, if you want to change the name then you have to change it twice (since those are disjoint events now). Can try using the same ID for both events, but I’m not sure if that will be allowed. Anyway feel free to experiment with this! Lmk if you find anything interesting / have questions 🍻