[Ietf-calsify] What is the appropriate serialization for a recurring event with one event changed?

Jeffrey Harris jeffrey at skyhouseconsulting.com
Mon Oct 3 16:41:30 PDT 2005

Hi Folks,

I've been working a bit with Oracle's CalDAV server and Apple's iCal,
and they have pretty different behaviors when serializing a recurring
event with a change to one event.

Lets take, for example, a daily event, starting Monday at 9AM, last
occurrence Friday at 9AM.  If I change Wednesday's event to 11AM, what
should the resulting stream look like?

iCal exports this as two VEVENTs, one has (omitting lots of other lines):


the other VEVENT has

RECURRENCE-ID:20051005T160000Z          #Wednesday at 9AM PDT (in UTC)
DTSTART;TZID=US/Pacific:20051005T110000 #Wednesday at 11AM PDT

Oracle's stream also has two VEVENTs:

EXDATE:20051005T160000Z                #Wednesday at 9AM PDT (in UTC)

the other VEVENT has

RECURRENCE-ID:20051005T180000Z         #Wednesday at *11AM* PDT (in UTC)

Is one of these more correct than the other?  Is an EXDATE appropriate
for the original time if an event's time has been moved?  What does it
mean for a RECURRENCE-ID to reference a time that isn't already in the
recurrence set?


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