Issue Summary

Team Calendar - 'Export to iCalendar' generates .ics files that is in violation to RFC 5545 rule.

The calendar data contained in an iCalendar file (.ics) must conform to RFC 5545 rules. According to RFC 5545, an event (VEVENT) is a data object that consists of several properties.

RRULE and RECURRENCE-ID cannot be used simultaneously in a single VEVENT due to the role of the properties.

RRULE: RFC 5545 Section 3.8.5.3
Attributes that define a pattern of repeating schedules
RECURRENCE-ID: RFC 5545 Section 3.8.4.4
Properties that identify instances on a specific day in an existing recurring schedule

The .ics file is generated with the below two fields for VEVENT.

RRULE:FREQ=DAILY;INTERVAL=1
RECURRENCE-ID;TZID=Australia/Sydney:20250320T080000

Steps to Reproduce

Consistently reproduced - Yes.

1. Create a Sub Calendar in the Confluence Calendar.
2. Set it as a repeating event, occurring every day.
3. Modify one of the events in the sequence.
   1. e.g. Change the time and/or the summary.
4. Export the calendar as a `.ics` file.

Expected Results

The .ics file is created that does not violate the RFC 5545 rule.

Either this

RRULE:FREQ=DAILY;INTERVAL=1

or this is allowed in a single VEVENT section.

RECURRENCE-ID;TZID=Australia/Sydney:20250320T080000

Actual Results

The .ics file is generated with the below two fields for VEVENT.

RRULE:FREQ=DAILY;INTERVAL=1
RECURRENCE-ID;TZID=Australia/Sydney:20250320T080000

Full .ics file attached.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available