Temporal.PlainMonthDay()

{{SeeCompatTable}}

The Temporal.PlainMonthDay() constructor creates {{jsxref("Temporal.PlainMonthDay")}} objects.

This constructor allows you to create instances by directly supplying the underlying data. Like all other Temporal classes, you should usually construct Temporal.PlainMonthDay objects using the {{jsxref("Temporal/PlainMonthDay/from", "Temporal.PlainMonthDay.from()")}} static method, which can handle a variety of input types.

Syntax#

new Temporal.PlainMonthDay(month, day)
new Temporal.PlainMonthDay(month, day, calendar)
new Temporal.PlainMonthDay(month, day, calendar, referenceYear)

[!NOTE] Temporal.PlainMonthDay() can only be constructed with new. Attempting to call it without new throws a {{jsxref("TypeError")}}.

[!WARNING] Avoid using the calendar and referenceYear parameters, because {{jsxref("Temporal/PlainMonthDay/equals", "equals()")}} will consider the reference year for equality, causing two equivalent month-days to be considered different if they have different reference years. To create a Temporal.PlainMonthDay object with a non-ISO calendar, use the {{jsxref("Temporal/PlainMonthDay/from", "Temporal.PlainMonthDay.from()")}} static method.

Parameters#

• month
• : A number, truncated to an integer, representing the month in the ISO calendar system.
• day
• : A number, truncated to an integer, representing the day of the month in the ISO calendar system.
• calendar {{optional_inline}}
• : A string representing the calendar to use. See Intl.supportedValuesOf() for a list of commonly supported calendar types. Defaults to "iso8601". Note that irrespective of the calendar, the referenceYear, month, and day must be in the ISO 8601 calendar system.
• referenceYear {{optional_inline}}
• : A number, truncated to an integer, representing the year in the ISO calendar system. Defaults to 1972. The same ISO month-day can represent different dates in different years with non-ISO calendars. For example, the days 2021-07-01 and 1972-07-01 may fall on different month-days in a non-Gregorian calendar, and just specifying "07-01" is insufficient to unambiguously determine a month-day in the target calendar. Therefore, you virtually always want to specify a referenceYear when using a non-ISO calendar.

Return value#

A new Temporal.PlainMonthDay object, representing the month-day of the date specified by referenceYear, month, day (in the ISO calendar), interpreted in the calendar system specified by calendar.

Exceptions#

• {{jsxref("TypeError")}}
• : Thrown if calendar is not a string or undefined.
• {{jsxref("RangeError")}}
• : Thrown in one of the following cases:
  • referenceYear, month, or day is not a finite number.
  • The referenceYear, month, and day combination does not represent a valid date in the ISO calendar system, or is not in the representable range, which is ±(10⁸ + 1) days, or about ±273,972.6 years, from the Unix epoch.
  • calendar is not a valid calendar identifier.

Examples#

Using Temporal.PlainMonthDay()#

const md = new Temporal.PlainMonthDay(7, 1);
console.log(md.toString()); // 07-01

const md2 = new Temporal.PlainMonthDay(7, 1, "chinese");
console.log(md2.toString()); // 1972-07-01[u-ca=chinese]

const md3 = new Temporal.PlainMonthDay(7, 1, "chinese", 2021);
console.log(md3.toString()); // 2021-07-01[u-ca=chinese]

Improper usage#

You should avoid using the calendar and referenceYear parameters, unless you know that the referenceYear is the canonical reference year that would be selected by Temporal.PlainMonthDay.from() for the same month-day.

const md = new Temporal.PlainMonthDay(7, 1, "chinese", 2021);
const md2 = Temporal.PlainMonthDay.from("2021-07-01[u-ca=chinese]");
console.log(md.equals(md2)); // false
console.log(md.toString()); // 2021-07-01[u-ca=chinese]
console.log(md2.toString()); // 1972-07-02[u-ca=chinese]

Specifications#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• {{jsxref("Temporal.PlainMonthDay")}}
• {{jsxref("Temporal/PlainMonthDay/from", "Temporal.PlainMonthDay.from()")}}