Cyclic year doesn't show up in resolvedOptions

In CreateDateTimeFormat, it says:

For each row in Table 7, except the header row, in table order, do
a. Let prop be the name given in the Property column of the row.
b. If bestFormat has a field [[<prop>]], then
i. Let p be bestFormat.[[<prop>]].
ii. Set dateTimeFormat's internal slot whose name is the Internal Slot column of the row to p.

In Table 7, the year is stated as being either "numeric" or "2-digit". However, this is clearly not reflected in the Chinese calendar resolvedOptions, which uses r and U (related Gregorian and cycle year name):

new Intl.DateTimeFormat("en", { calendar: "chinese", year: "numeric" }).format(new Date())
// '2023(gui-mao)'
new Intl.DateTimeFormat("en", { calendar: "chinese", year: "numeric" }).resolvedOptions()
// {locale: 'en', calendar: 'chinese', numberingSystem: 'latn', timeZone: 'America/Los_Angeles'}

It works fine in formatToParts:

0: {type: 'relatedYear', value: '2023'}
1: {type: 'literal', value: '('}
2: {type: 'yearName', value: 'gui-mao'}
3: {type: 'literal', value: ')'}

Per 11.2.3 Internal slots, "{relatedYear}" can only appear in a pattern string when the format record has a [[year]] field. And if a [[year]] field is present, CreateDateTimeFormat will set the Intl.DateTimeFormat's [[Year]] field to the format records [[year]] value. Intl.DateTimeFormat.prototype.resolvedOptions should then return the value of the [[Year]] internal slot.

IOW this seems to be spec'ed correctly, it's just that engines don't implement this correctly.

As long as the pattern string can't contain both "{year}" and "{relatedYear}", engines simply have to map the 'r' and 'U' Date Field Symbols to year: "numeric". (The related-year can only be "numeric", never "2-digit".)

Bug 1855748: Handle related year and year names when computing the re…

TG2 discussion: https://github.com/tc39/ecma402/blob/main/meetings/notes-2026-09-17.md#cyclic-year-doesnt-show-up-in-resolvedoptions-816

Let's fix this

TG2 discussion: https://github.com/tc39/ecma402/blob/main/meetings/notes-2026-10-08.md#issue-816---cyclic-year-doesnt-show-up-in-resolvedoptions

The spec seems correct, but the engines are not correct. Please add test262.

PARTIAL Test date defaults

Test date defaults

I've submitted tests for review here: tc39/test262#5155

Navigation Menu

Repository navigation

Cyclic year doesn't show up in resolvedOptions #816

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Cyclic year doesn't show up in resolvedOptions #816

Description

Activity

anba commented on Aug 7, 2023

sffc commented on Sep 23, 2026

sffc commented on Oct 15, 2026

jugglinmike commented on Oct 21, 2026

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions