[Feature Request] Grouping iCalendar event with RRULE

[Victrid]

Most classes are planned weekly or biweekly, it could be better to use recurrence rule defined in iCalendar specifications. This will allow calendar app users to edit their events efficiently.

[skyzh]

We need to consider two cases:

• How to handle holidays?
• How to handle courses that occur at 3, 5, 7, 11 weeks?

If these could be easily handled with RRULE, I'm willing to make the change.

[Victrid]

Though it could be pretty dumb, it can be done by BYYEARDAY in RRULE. This is an example that the event is set to happen on 2021-09-15, 2021-09-16, and 2021-10-26.

BEGIN:VCALENDAR
...
BEGIN:VEVENT
DTSTAMP:20210918T024340Z
CREATED:20210918T024340Z
LAST-MODIFIED:20210918T024340Z
SUMMARY:test
RRULE:FREQ=YEARLY;UNTIL=20220101T050000Z;BYYEARDAY=258, 259, 299
EXDATE;TZID=Asia/Shanghai:20210918T130000
DTSTART;TZID=Asia/Shanghai:20210915T130000
DTEND;TZID=Asia/Shanghai:20210915T144000
TRANSP:OPAQUE
END:VEVENT
END:VCALENDAR 

As long as the course is arranged the same time on clock, it can be grouped. As the iCalendar exported hard-coded every event's time, and as courses' range less than 1 year, the RRULE is actually appointing unique dates. It would not be hard to implement for your cases.

[Victrid]

This feature is written in RFC5545, so calendar app supporting iCalendar should have the support.

[Victrid]

Take ME210/SI1210 工程实践 as an example, this course has no location on the schedule and the actual course time is 12:55-17:40 instead of 12:00-17:40 on i.sjtu.edu.cn, it would be more convenient to change all the course information at once.

[skyzh]

LGTM to me. I'll add this support sometime later.

[skyzh]

What if the course crosses two years? e.g. a 2021 fall course may span 2021 and 2022.

[Victrid]

you could assign the BYYEARDAY like 362, 363, 364, 365, 1, 2, 3, 4, and set the start day (DTSTART) and end day (RRULE/UNTIL) to limit them in 2021-09 to 2022-02.