Re: [POLL] Dealing with +1m/y repeaters when jumping to impossible date (should 05-31 +1m be 07-01 or 06-30?)

[Max Nikulin <manikulin@gmail.com>]

On 06/04/2024 01:34, Ihor Radchenko wrote:
> Generally, I did see several requests to change the strategy when
> calculating next month/year. However, that would be a breaking change.
> I'd only go for it if people are strongly in favor of the change.
> So, changing this to a poll.

I think the following should be taken into account: behavior of popular 
calendar applications, specifications they implement, libraries that 
likely used to create such applications.

Should it be configurable per user, per file, or even per rule 
(timestamp with repeater)?

I am not familiar with RFC5545 iCalendar, so I am unsure what options it 
recommends.

An example of recently designed library (however Org does not support 
calendars with leap *months*):
<https://tc39.es/proposal-temporal/docs/calendar.html#handling-unusual-dates-leap-days-leap-months-and-skipped-or-repeated-periods>
"Handling unusual dates: leap days, leap months, and skipped or repeated 
periods" (Temporal proposal for JavaScript)

> When Temporal encounters inputs representing a month and/or day that
> doesn't exist in the desired calendar year, by default (overridable in
> with or from via the overflow option) the inputs will be adjusted using
> the following algorithm:
> 
> - First, pick the closest day in the same month. If there are two
> equally-close dates in that month, pick the later one.
> - If the month is a leap month that doesn't exist in the desired year,
> then pick another date according to the cultural conventions of that
> calendar's users. Usually this will result in the same day in the month
> before or the month after where that month would normally fall in a leap
> year.
> - Otherwise, pick the closest date to the provided date that is still in
> the same year. If there are two equally-close dates, pick the later one.
> - If the entire year doesn't exist, then pick the closest date to the
> provided date. If there are two equally-close dates, pick the later one.