Comment 2 for bug 117817

Yes we only test for intersection with first event in the chain. The heuristics could be improved i guess, but implementing a system that would find whether there is a possible intersection between 2 infinitely recurring events is very difficult and not very feasible so i am marking this as a "Wishlist".

If you want to you can try and come up with some kind of clever algorithm, i will gladly accept patches that fix this problem.

As for your current code:

    def getConflictingEvents(self, resource):
        """Return a list of events that would conflict when booking resource."""
        events = []
        if not canAccess(resource.calendar, "expand"):
            return events
        if self.context.recurrence:
          totest = []
          # this loop is infinite when you have an infinite recurrence rule
          for d in self.context.recurrence.apply(self.context):
              totest.append(datetime(d.year, d.month, d.day, self.context.dtstart.hour, self.context.dtstart.minute, self.context.dtstart.second, self.context.dtstart.microsecond, self.context.dtstart.tzinfo))
        else:
          totest = [self.context.dtstart]
        for d in totest:
          # expanding each of the events let's say 300 times (because we have a daily recurring event for a year)
          for event in resource.calendar.expand(d,d + self.context.duration):
            # for every one of like 100 events in the resource calendar
            # and we show at least 10 resources
            # i am afraid this would be too slow :(
            if event != self.context:
                  events.append(EventForBookingDisplay(event))
        return events