Temporal PlainYearM

The Temporal.PlainYearMonth Object

The Temporal.PlainYearMonth object is a year and month object.

It represents the year and month of an ISO 8601 calendar without day or time.

Example: 2026-05.

How to Create a PlainYearMonth Object

An PlainYearMonth object can be created in different ways:

Create a PlainYearMonth with new

The new PlainYearMonth() constructor creates a new PlainYearMonth object with integers as input parameters.

Example

// Create a PlainYearMonth object

const date = new Temporal.PlainYearMonth(2026, 5);

PlainYearMonth from( object )

The from() method creates a new PlainYearMonth object with an object as input parameter.

Example

// Create a PlainYearMonth object

const date = new Temporal.PlainYearMonth({year:2026, month:5});

PlainYearMonth from( RFC 9557 )

The from() method creates a new PlainYearMonth object with an ISO / RFC 9557 string as input parameter.

Examples

// Create a PlainYearMonth object

const date = Temporal.PlainYearMonth.from("2025-05");

Note: that the day input is ignored in the last example.

Temporal.PlainYearMonth Properties

Display All PlainYearMonth Properties

const date = new Temporal.PlainYearMonth(2026, 5);

Convert to PlainTime

Example

const yearMonth = new Temporal.PlainYearMonth(2026, 5);

const date = yearMonth.toPlainDate({ day: 17 });

PlainYearMonth add() and subtract()

The add() method accept a duration object as input.

Example

// Create a new PlainYearMonth object

const d1 = Temporal.PlainYearMonth.from("2026-05");

// Add a duration

const d2 = d1.add({years:2, months:2})

All temporal objects have their own add() method:

• duration.add(duration)
• instant.add(duration)
• plaindate.add(duration)
• plaintime.add(duration)
• plainyearmonth.add(duration)
• plainmonthday.add(duration)
• plaindatetime.add(duration)
• zoneddatetime.add(duration)

All temporal objects have their own subtract() method:

• duration.subtract(duration)
• instant.subtract(duration)
• plaindate.subtract(duration)
• plaintime.subtract(duration)
• plainyearmonth.subtract(duration)
• plainmonthday.subtract(duration)
• plaindatetime.subtract(duration)
• zoneddatetime.subtract(duration)

Note: Learn More: JavaScript Temporal Arithmetic

The with() Method

The with() method returns a new PlainYearMonth object with specified field(s) replaced.

Example

// Create a PlainYearMonth object

const date = Temporal.PlainYearMonth.from("2026-05");

// Replace month

const newDate = date.with({ month:12 });

All PlainYearMonth Methods

All PlainYearMonth Properties