8000 Constants for the minimum and maximum values of each Temporal type · Issue #23 · js-temporal/proposal-temporal-v2 · GitHub
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Constants for the minimum and maximum values of each Temporal type #23

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ptomato opened this issue Mar 17, 2022 · 0 comments
Open

Constants for the minimum and maximum values of each Temporal type #23

ptomato opened this issue Mar 17, 2022 · 0 comments

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@ptomato
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ptomato commented Mar 17, 2022

Several Temporal types have an allowed range of values (tc39/proposal-temporal#24):

  • Instant, ZonedDateTime: ±1e8 24-hour days around the Unix epoch (±86400_0000_0000_000_000_000n nanoseconds), same as legacy Date
    • min value: -271821-04-20T00:00:00Z
    • max value: +275760-09-13T00:00:00Z
  • PlainDateTime: such that any valid Instant can be converted to a PlainDateTime at any UTC offset in the range of ±23:59:59.999999999
    • min value: -271821-04-19T00:00:00.000000001
    • max value: +275760-09-13T23:59:59.999999999
  • PlainDate: such that any valid PlainDateTime can be converted to a PlainDate
    • min value: -271821-04-20
    • max value: +275760-09-13
  • PlainYearMonth: such that any valid PlainDate can be converted to a PlainYearMonth
    • min value: -271821-04
    • max value: +275760-09

It's not currently possible to get these values from JS, except by knowing what they are through out-of-band documentation.

One recommendation would be to include constants on each type's constructor (e.g. Temporal.Instant.MAX_VALUE). This would avoid polluting top-level autocomplete with a large number of rarely used options. Also it would match other types' behavior like Number.

Advantages:

These are useful for input validation, expanded polyfills, and tests.

Concerns:

None, this seems useful to have.

Prior art:

  • Legacy Date has a Date object where the internal date value is NaN, but no min or max value constants
  • Python: datetime.datetime.max, etc.
  • Rust: chrono::MAX_DATE, etc.

Constraints / corner cases:

  • What calendar would the min and max values for ZonedDateTime, PlainDate, PlainDateTime, and PlainYearMonth have? iso8601 as the "machine" calendar might be the answer here.
  • What time zone would the min and max values for ZonedDateTime have? Unlike the calendar, it seems like it could be harmful to choose UTC as the time zone.
  • Would we have max and min values for PlainTime (00:00–23:59:59.999999999)?
  • Would we have max and min values for PlainMonthDay (01-01–??-??)? The max value depends on the calendar. For example, the Gregorian calendar would have 12-31 as the max value, and the Hebrew calendar would have a max value of PlainMonthDay.from({ monthCode: 'M12', day: 29 })(?)
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