Subject: [Ietf-calsify] Another recurrence rule question

From: reinhold at kainhofer.com (Reinhold Kainhofer)
Date: Wed Nov 15 06:19:52 2006

Hi all,

Another issue to be cleared in a possible clearing FAQ about RFC 2445.

In a weekly recurrence rule, when exactly is the weekday (Monday, Tuesday, 
etc.) taken from DTSTART and when not.
In particular, take a recurrence rule:
   RRULE:FREQ=WEEKLY
This event recurs every week on the same weekday as DTSTART.

Now, what about:
  RRULE:FREQ=WEEKLY;BYMONTHDAY=15
Does this event recur on every 15 of each month, regardless of the weekday, or 
on every 15th of each month if it is the same weekday as DTSTART?

In other words, does FREQ=WEEKLY always imply an implicit BYDAY=.. (value 
taken from DTSTART)?

Cheers,
Reinhold
-- 
------------------------------------------------------------------
Reinhold Kainhofer, Vienna University of Technology, Austria
email: [email-masked], http://reinhold.kainhofer.com/
 * Financial and Actuarial Mathematics, TU Wien, http://www.fam.tuwien.ac.at/
 * K Desktop Environment, http://www.kde.org, KOrganizer maintainer
 * Chorvereinigung "Jung-Wien", http://www.jung-wien.at/

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From: cyrus at daboo.name (Cyrus Daboo)
Date: Wed Nov 15 07:13:53 2006

Hi Reinhold,

--On November 15, 2006 3:19:41 PM +0100 Reinhold Kainhofer 
<[email-masked]> wrote:

> In a weekly recurrence rule, when exactly is the weekday (Monday,
> Tuesday,  etc.) taken from DTSTART and when not.
> Does this event recur on every 15 of each month, regardless of the
> weekday, or  on every 15th of each month if it is the same weekday as
> DTSTART?
>

I don't see why FREQ=WEEKLY should imply any implicit BYDAY= part. It just 
means repeat the first instance at 7 day intervals. It does not matter what 
day the first instance is. Of course repeating every 7 days means that you 
will always repeat on the same day of the week.

Remember: one change we have agreed upon is that the DTSTART must now match 
the RRULE. So if you did:

The DTSTART would have to be the 15th of some month. The week day does not 
enter into it - other than the fact that that is the weekday for all 
instances. If you did:

RRULE:FREQ=WEEKLY;BYMONTHDAY=15;BYDAY=TU

then you would have to specific a DTSTART that was the 15th of some month 
AND a Tuesday.

-- 
Cyrus Daboo