Temporal.PlainDate.prototype.monthsInYear
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 monthsInYear
accessor property of Temporal.PlainDate
instances returns a positive integer representing the number of months in the year of this date. It is calendar-dependent.
For the ISO 8601 calendar, this is always 12, but in other calendar systems it may differ. For example, in calendars using leap months, leap years will have one more month than common years.
The set accessor of monthsInYear
is undefined
. You cannot change this property directly.
Examples
Using monthsInYear
const date = Temporal.PlainDate.from("2021-07-01");
console.log(date.monthsInYear); // 12
const date2 = Temporal.PlainDate.from("2021-07-01[u-ca=chinese]");
console.log(date2.monthsInYear); // 12
const date3 = Temporal.PlainDate.from("2023-07-01[u-ca=chinese]");
console.log(date3.monthsInYear); // 13; 2023 is a Chinese leap year
Changing to the second last month of the year
You can use monthsInYear
to change to the second last month of the year:
const date = Temporal.PlainDate.from("2021-07-01");
const secondLastMonth = date.with({ month: date.monthsInYear - 1 });
console.log(secondLastMonth.toString()); // 2021-11-01
Specifications
Specification |
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Temporal proposal # sec-get-temporal.plaindate.prototype.monthsinyear |
Browser compatibility
Report problems with this compatibility data on GitHubdesktop | mobile | server | ||||||||||||
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monthsInYear |
Legend
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- No support
- No support
- Experimental. Expect behavior to change in the future.
- See implementation notes.
- User must explicitly enable this feature.