Subject: [Ietf-calsify] RFC2445bis: Anniversary-style dates

From: benfortuna at gmail.com (Ben Fortuna)
Date: Sat May 26 23:00:54 2007

Hi all,

Apologies if this is off-topic, too late, or just plain painful to
discuss (!), but I've noticed in the draft specification that
anniversary-style dates (i.e. events containing DTSTART with
VALUE=DATE and no DTEND or DURATION), are now assumed to have a
duration of one (1) day as follows (3.6.1):

      For cases where a "VEVENT" calendar component
      specifies a "DTSTART" property with a DATE value type but no
      "DTEND" nor DURATION property, the event's duration is taken to be
      one day.

Is there an assumption also being made as to the time that this
duration starts? I ask this because the representation of a period of
time requires the start (and end) of the period to be specified as a
DATE-TIME component (3.3.9):

        period     = period-explicit / period-start

        period-explicit = date-time "/" date-time
        ; [ISO.8601.1988] complete representation basic format for a
        ; period of time consisting of a start and end. The start MUST
        ; be before the end.

        period-start = date-time "/" dur-value
        ; [ISO.8601.1988] complete representation basic format for a
        ; period of time consisting of a start and positive duration

So if anniversary-style dates now have a default duration, but no
specific time for the start of the duration, I still see a problem
with how to represent that event's time consumption using a period of
time. I think this is also an issue for events that do specify a
DTEND, but both DTEND and DTSTART have VALUE=DATE.

Thanks for any clarification of this issue.

regards,
ben

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From: benfortuna at gmail.com (Ben Fortuna)
Date: Sun May 27 00:53:44 2007

Ok, I've just discovered there has been plenty of discussion on this
topic, courtesy of the Bedework wiki:

http://www.bedework.org/trac/bedework/wiki/Bedework/DevDocs/DtstartEndNotes

Looks like the assumption is that DATE-based DTSTART/DTEND properties
start at midnight, and have a duration of 23:59:59 hours (i.e.
exclusive of midnight the next day). I'm not sure if this can be
further clarified in the draft spec, but I think there is still
potential for misinterpretation in it's current form.

regards,
ben

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From: cyrus at daboo.name (Cyrus Daboo)
Date: Sun May 27 06:56:35 2007

Hi Ben,

> potential for misinterpretation in it's current form.

Strictly speaking the duration is 24 hours not 23:59:59.

The spec is already pretty clear that DTEND represents the exclusive end of 
the time period, and I think that is implicit in the description of 
DTSTART;VALUE=DATE with a DTEND (or DURATION).

For VALUE=DATE, the proper "timed" interpretation is that of a floating 
time event set to start at 00:00:00 on the start date (inclusive) and end 
at 00:00:00 on the end date (exclusive).

-- 
Cyrus Daboo