Temporal.PlainDate.prototype.eraYear

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The eraYear accessor property of Temporal.PlainDate instances returns a non-negative integer representing the year of this date within the era, or undefined if the calendar does not use eras (e.g. ISO 8601). The year index usually starts from 1 (more common) or 0, and years in an era can decrease with time (e.g. Gregorian BCE). era and eraYear together uniquely identify a year in a calendar, in the same way that year does. It is calendar-dependent.

Unlike year, era and eraYear may change in the middle of a calendar year. For example, Japan started the Reiwa era on May 1, 2019, so dates from 2019-01-01 to 2019-04-30 have { era: "heisei", eraYear: 31 }, and dates from 2019-05-01 onwards have { era: "reiwa", eraYear: 1 }, but the year is always 2019 (because the Japanese calendar uses the ISO 8601 year as the default year).

The set accessor of eraYear is undefined. You cannot change this property directly. Use the with() method to create a new Temporal.PlainDate object with the desired new value.

Examples

Using eraYear

js
const date = Temporal.PlainDate.from("2021-07-01"); // ISO 8601 calendar
console.log(date.eraYear); // undefined

const date2 = Temporal.PlainDate.from("2021-07-01[u-ca=gregory]");
console.log(date2.eraYear); // 2021

const date3 = Temporal.PlainDate.from("-002021-07-01[u-ca=gregory]");
console.log(date3.eraYear); // 2022; 0000 is used for the year 1 BC

const date4 = Temporal.PlainDate.from("2021-07-01[u-ca=japanese]");
console.log(date4.eraYear); // 3

Changing eraYear

You can only set eraYear for calendars that support them. For example, the ISO 8601 calendar does not have eras. Note that you must provide era and eraYear together.

js
const date = Temporal.PlainDate.from("2021-07-01[u-ca=gregory]");
const newDate = date.with({ era: "bc", eraYear: 100 });
console.log(newDate.toString()); // -000099-07-01[u-ca=gregory]

const date2 = Temporal.PlainDate.from("2021-07-01[u-ca=japanese]");
const newDate2 = date2.with({ era: "meiji", eraYear: 1 });
console.log(newDate2.toString()); // 1868-07-01[u-ca=japanese]

Specifications

Specification
Temporal proposal
# sec-get-temporal.plaindate.prototype.erayear

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
eraYear
Experimental

Legend

Tip: you can click/tap on a cell for more information.

No support
No support
Experimental. Expect behavior to change in the future.
See implementation notes.
User must explicitly enable this feature.

See also