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

[Marten Gajda <[e-mail]>]

Am 03.02.2015 um 22:04 schrieb Cyrus Daboo:
> I think Ken's idea is that you apply the SKIP after BYMONTH only if 
> the invalid data corresponds to an invalid leap month as opposed to a 
> leap day. In which case the SKIP would not have applied after BYMONTH 
> in your example. But I think a behavior like that is going to be 
> really tricky for implementors to get right and hard to describe 
> really well without having to delve into the gory details of RRULE 
> processing.
>
Ah, got it.

So, considering the following

Applying SKIP=FORWARD after BYDAY on the following rule

FREQ=YEARLY;RSCALE=HEBREW;MONTHLY=5L;BYDAY=MO,TU,WE,TH,FR,SA,SU;SKIP=FORWARD

results in 30 instances in leap years and in non-leap years, since it 
would expand the week days in Adar I and roll them forward afterwards

Applying SKIP=FORWARD after BYMONTH but before BYDAY results in 30 
instances in leap years, but 29 instances in non-leap years, since the 
weekdays would be expanded for Adar instead of Adar I.

It's similar when the month following the leap month has more days than 
the leap month itself.

In essence, applying SKIP after all BYxxx parts won't change the number 
of instances (given they don't fall on another instance), but Ken's 
approach might do that.

Not sure what's preferable in this case.



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*Marten Gajda*
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