> a date with a calendar associated but no time or timezone (might be due to being implied but also might be irrelevant, like in birthdates).
It might also be relevant: Ever ask an older Korean person their age?
> Instant: a fixed point in time with no calendar or location. Think e.g. "the user logged in at X date and time" but valid across the world for any timezone or calendar system. This is what we usually use "Unix UTC timestamps" for.
This is not a thing. Those are intervals to some Epoch, maybe taking into account leap-seconds and maybe not. They are not very useful except grossly over long ranges.
> - ZonedDateTime: like an Instant but associated with a particular calendar and location. Think an Instant but rendered "real" into a calendar system and timezone so the user can see a meaningful time for them.
Like when a user logged in at X date and time. They don't do this from no location, but from some location.
> - PlainDate: already discussed. Think e.g. birthdates.
And already wrong.
> - PlainTime: think "run task every day at 6:30pm".
Erm no. You can say 18:30 hours after midnight, or you can say when the calendar says 6:30pm, but these are different things. Imagine the poor fool who wants to run the task every day at "1:30am" and has it run twice on some days.
Bars close in some parts of the world at 30h (30時) to mean 6am the following day.
> - PlainDateTime: like an Instant but associated with a calendar system, but no timezone. Think e.g. what a user would insert in a datetime picker, where the timezone is implied instead of explicitly selected.
No, like a string.
> - PlainYearMonth: think e.g. "we'll run our reports during October 2025".
Nonsense. Also a string.
> - PlainMonthDay: think e.g. "my birthday is June 13".
Your birthday might be on the 29th of January. You cannot do reasonable arithmetic with
such things, so it might as well be a string like many of these others.
> I like how Temporal[0] does this.
I don't if you can't tell. This stuff is complicated and I'd like more people exploring it because I don't know The Right Answer™ either, but I know enough to know that every existing solution is wrong in some way that can cause real harm.