Re: [calsify] SKIP was Re: AD review of draft-ietf-calext-rscale-03

[Ken Murchison <[e-mail]>]

On 02/03/2015 12:58 PM, Ken Murchison wrote:
> On 02/03/2015 12:51 PM, Cyrus Daboo wrote:
>> Hi Ken,
>>
>> --On February 3, 2015 at 12:38:52 PM -0500 Ken Murchison 
>> <[e-mail]> wrote:
>>
>>> I believe we can get by with just a single SKIP and your previous rules
>>> to handle both cases above (using Hebrew leap month):
>>>
>>> RRULE:FREQ=YEARLY;RSCALE=HEBREW;SKIP=FORWARD;BYMONTH=5L;BYMONTHDAY=30
>>>
>>> Would yield 1 Nisan (skipping forward both a month and day)
>>>
>>>
>>> RRULE:FREQ=YEARLY;RSCALE=HEBREW;SKIP=FORWARD;BYMONTH=5L;BYMONTHDAY=-1
>>>
>>> Would yield 29 Adar (skipping forward just a month)
>>>
>>
>> Actually I am not convinced about that since the spec says that SKIP 
>> is applied AFTER all other rule parts are processed (except for 
>> BYSETPOS, COUNT and UNTIL). So the BYMONTHDAY=-1 refers to the last 
>> day of the invalid month, 30 Adar I, which then becomes the invalid 
>> date 30 Adar after the month skip and then 1 Nisan after the day skip.
>
> Hmm, I think you're right based on the current wording.  I don't 
> recall exactly how we decided on that wording, but perhaps it might 
> needs to be adjusted.

Looking at RFC 5545:

       If multiple BYxxx rule parts are specified, then after evaluating
       the specified FREQ and INTERVAL rule parts, the BYxxx rule parts
       are applied to the current set of evaluated occurrences in the
       following order: BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY, BYDAY,
       BYHOUR, BYMINUTE, BYSECOND and BYSETPOS; then COUNT and UNTIL are
       evaluated.


I'm wondering if we shouldn't have SKIP applied both immediately 
following BYMONTH and BYMONTHDAY evaluation.  I don't think we want the 
other BYxxx rule parts to be operating on invalid dates at any point.  
Thoughts?

-- 
Kenneth Murchison
Principal Systems Software Engineer
Carnegie Mellon University