Subject: Semantics of date vs. date/time EXDATEs

From: Federico Mena Quintero <[email-masked]>
Date: Wed, 28 Feb 2001 12:38:36 -0600

Let's say I have a recurring event.  If I add EXDATE properties, what
is the difference between making them date or date/time values?  

Does a date/time value only affect occurrences whose start time is
precisely that date/time?  And does a date value affect all
occurrences that happen during that day, or just the ones whose start
time is midnight?

  Federico

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From: John Stracke <[email-masked]>
Date: Wed, 28 Feb 2001 14:02:49 -0500

> is the difference between making them date or date/time values?

Uh...<checks RFC-2445, 4.8.5.1>...it doesn't say.  Good catch.

> occurrences that happen during that day

That's what I would guess would be the expected behavior.  Anybody else?

The problem is that EXDATE says:

     excluding any start date and times which fall within the union
     of start date and times generated by any specified "EXRULE"
     and "EXDATE" properties.

...but doesn't define how that union is generated.

--
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|John Stracke    | http://www.ecal.com |My opinions are my own.   |
|Chief Scientist |================================================|
|eCal Corp.      |"Where's your sense of adventure?" "Hiding under|
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From: "Graham Gilmore" <[email-masked]>
Date: Wed, 28 Feb 2001 14:28:23 -0500

----- Original Message -----
From: "John Stracke" <[email-masked]>
To: <[email-masked]>
Sent: 28 February, 2001 14:02
Subject: Re: Semantics of date vs. date/time EXDATEs

> That's what I would guess would be the expected behavior.  Anybody
else?

    I would interpret it that way as well.

> ...but doesn't define how that union is generated.

    There's a couple of related issues already listed at
http://www.softwarestudio.org/iCal/2445Issues.html :

        - http://www.imc.org/ietf-calendar/mail-archive/msg02600.html ,
where Frank Dawson suggests that mixed DATE & DATE-TIME value types be
prohibited in an iCalendar object.

        - http://www.imc.org/ietf-calendar/mail-archive/msg04949.html ,
where Damon Chaplin explores some interpretations of DATE values for
different properties.

    Both of these are marked as 'open'.  Does that mean there hasn't
been a consensus on them, or just that they haven't been formally added
to the spec yet?

    Graham

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From: Federico Mena Quintero <[email-masked]>
Date: Wed, 28 Feb 2001 13:44:29 -0600

> That's what I would guess would be the expected behavior.  Anybody else?

Okay.  So I will fix our code to do that.  This really needs to be
specified in the RFC, which is annoyingly ambiguous about recurrences.

> ...but doesn't define how that union is generated.

Generating the union is obvious enough; you just expand EXRULEs and
put in EXDATEs.  What it does not say is what to do with the results.

  Federico

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From: Damon Chaplin <[email-masked]>
Date: Thu, 01 Mar 2001 00:58:12 +0000

> occurrences that happen during that day, or just the ones whose start

We had a similar discussion last November (subject was "Recurrence
UNTIL/RDATE/EXDATE properties with DATE values").

There wasn't much discussion, but I think the consensus was (well,
mainly from Bruce Kahn):

For EXDATEs, a date value excludes all occurrences on that day.

For RDATE and UNTIL, a date value means that the time is inherited from
the DTSTART value.

Can we agree on this and add it to the spec before we get interoperability
problems?

Damon