A.7. Repeating Events and Recurrence Rules

The biggest problem in the area of repeating meetings is devices that claim they can support repeating meetings but which in reality can only support a very small subset of the repeating capabilities that iCalendar provides for.

For devices that simply don’t claim any sort of repeating support server-side implementations should expand all repeating events and send simple single instance events for all instances within the synchronization range. The fact that they are repeating should be maintained server-side and any modification done on the device side should not affect this. This means that users can’t deal with such entries as being repeating on the device but they at least always known when an instance is occurring.

It becomes much more complicated when the mobile device does claim support for repeating entries but does not fully support the concept. Often devices will support deleted exceptions but not modified exceptions or only support a small subset of recurrence rules. Whenever a server cannot reliably know what sort of support the device is claiming it should fallback to the method described above for devices with no support

Ideally, there should be a minimum level of support that mobile devices must have to claim they support repeating entries.

BOF Topic: What is this minimum level of support?

A server should fallback to splitting up instances for anything, which falls outside of this minimum implementation.