Re: DTSTART for recurrence instances

Craig Johnson wrote:

> Olivier presented an excellent case showing that a RECCURRENCE-ID's
> primary role is that of an 'identifier'; and not a 'date/time' value 
> that can
> be relied on as the 'effective start' for a recurrence instance.  This 
> is made
> even more clear in the following from 2445:
>  
> Section 4.8.4.4 Recurrence ID
> . . .
>    The date/time value (RECURRENCE-ID) is set to the time when the 
> original recurrence
>    instance would occur; meaning that if the intent is to change a
>    Friday meeting to Thursday, the date/time (RECURRENCE-ID) is still 
> set to the
>    original Friday meeting.

Meaning in the object being sent in the reschedule. In order to say X 
moves to Y,
you need to properties to hold X and Y. So the above paragraph means send a
new object with the new Y in RECURRENCE-ID and the old X in DTSTART.

> With RECURRENCE-ID consigned to the role of an identifier
> it clearly falls to DTSTART to represent a recurrence instance's
> effective start time.

2445 is talking about a reschedule object not what 2446 calls the master 
object.

> Doug wrote:
> > For a recurring instance the effective start of an instance
> > is defined in 2445 to be the RECURRENCE-ID.
>  
> That is not quite correct.  The effective start of an instance
> is its DTSTART.  RECURRENCE-ID gets DTSTART as its
> initial value:
>  
> 4.8.4.4 Recurrence ID
> . . .                                               The property
>    value is the effective value of the "DTSTART" property of the
>    recurrence instance.
>  
> This statement makes it clear that a recurrence instance has a
> DTSTART property containing the "effective" value  ... and this is
> where RECURRENCE-ID gets its initial value.  Initially, DTSTART
> and RECURRENCE-ID have the same value.  If the instance is
> changed to a different time, DTSTART changes and
> RECURRENCE-ID does not.

Yet the topic of the section is RECURRENCE-ID and not DTSTART, so the
subject usage 'THE" in that sentence is RECURENCE-ID and not DTSTART.

Yes RECURRENCE-ID is the effective DTSTART of the 'instance'. If you have 3
daily instances the effective DTSTART of the 1st is 4-DEC, 2nd 5-DEC, and
the 3rd 6-DEC.

So the value of recurrence ids are:

1st
   
    RECURRENCE-ID: 4-DEC

2nd

    RECURRENCE-ID:5-DEC

3rd

    RECURRENCE-ID:6-DEC

Is does not say the "the value of DTSTART is", it says the value [of 
recurrence-id]
is the effective value of DTSTART. Not the same meaning.

It also does not say the value of DTSTART and RECURRENCE-ID are both
set to the same value (as I understoon one person to have said).

-- 

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