JP: Remove Seven-Five-Three Festival and Christmas observance

[ys-spk]

Thanks for maintaining this very useful library.
I'd like to propose removing Seven-Five-Three Festival (七五三, 11-15) and Christmas Day (12-25) from the built-in JP locale.

I understand these aren't national holidays and that their type is correctly marked as observance (and I understand the distinction and the existing resolution in #159, #381 and #437).

The problem is the choice of which observances to include.
As can be seen from these issues and external blog posts (for example: Seven-Five-Three Festival and Christmas are not national holidays ), the combination of "legal holidays + Seven-Five-Three Festival + Christmas" feels arbitrary and difficult to justify as a default from a Japanese perspective.

If we are going to include non-official annual events at all, there are other candidates that are more commonly recognized as major seasonal events, for example:

• Hinamatsuri / Girls' Day (ひな祭り, 3-3)
• Tanabata (七夕, 7-7)
• Obon (お盆, from 8-13 to 8-16, when many companies effectively close)

If these events were included, having Christmas in the list would make sense to me, but even then I would still argue against including Seven-Five-Three Festival.
In modern practice, families visit shrines on various weekends in October and November rather than specifically on 11-15, so modelling it as a single "holiday-like" date is somewhat artificial.

[eddyleelin]

@ys-spk Although I'm not Japanese, it seems like the correct action would be to add those other 3 events that you had mentioned, and update the day(s) of observance for the Seven-Five-Three Festival (七五三)?

[ys-spk]

Thank you for the suggestion!
I agree that adding those three events is a step in the right direction, and that Christmas would feel more natural to keep if we had more observances.

However, my main concern is not the number of observances, but the lack of a clear rule for choosing them.

Once we start including non-official seasonal events in Japan, there are several different kinds, for example:

• events with a fixed date (e.g. Hinamatsuri / ひな祭り, Tanabata / 七夕),
• foreign-origin events with customs unique to Japan (e.g. Valentine's Day, Halloween),
• events that date depends on solar longitude (e.g. Setsubun / 節分, Midsummer Ox Day / 土用の丑の日),
• events based on the (no longer official) lunisolar calendar (e.g. Jugoya / 十五夜).

The further down this list you go, the more interesting it becomes from a calendar perspective (and it could more benefit from date-holidays' powerful rule system!), but also the harder it becomes to maintain.

From a Japanese perspective, that's why "national holidays + exactly a few hand-picked observances" tends to feel arbitrary, no matter which few we choose.
Seven-Five-Three Festival is especially tricky: in modern practice it doesn't really have a single date or fixed range.

So before adding more observances, I'd really like to hear from the maintainer what the intended design for the JP data is:

• Should it stay close to "legal/bank/optional holidays only" and leave cultural events to user-defined rules?
• Or should it aim to provide a richer set of observances, and if so, based on what inclusion criteria?

Depending on that decision, I'm happy to help with a PR (adding more observances, removing Seven-Five-Three Festival, or both).