Date

`Date.prototype.setMonth`

Sets the month for a specified date according to local time

Syntax

JavaScript

date.setMonth(monthValue, dayValue?)

Parameters

Parameter	Type	Description
monthValue	number	A zero-based integer (0-11)
dayValue	number	Optional day of the month

Return Value

The number of milliseconds from epoch for the updated date

Examples

Basic Usage

const date = new Date('2024-06-15');
date.setMonth(0); // January
console.log(date.getMonth()); // 0

Practical Example

function addMonths(date: Date, months: number) {
  const d = new Date(date);
  d.setMonth(d.getMonth() + months);
  return d;
}

Advanced Usage

const date = new Date('2024-01-31');
date.setMonth(1); // Feb - note: may overflow
console.log(date.getDate()); // Could be March 2

Understanding Date.prototype.setMonth

The Date.prototype.setMonth method in JavaScript sets the month for a specified date according to local time. It belongs to the Date object and is one of the most widely used methods for working with date values in modern JavaScript and TypeScript applications.

The method signature is date.setMonth(monthValue, dayValue?). It accepts 2 parameters: monthValue, dayValue. When called, it returns the number of milliseconds from epoch for the updated date. Understanding when and how to use setMonth() helps you write more expressive, readable code.

Common use cases for Date.prototype.setMonth include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like date-getmonth, date-setfullyear, date-setdate, enabling you to chain operations together for complex data manipulation pipelines.

Browser support for Date.prototype.setMonth is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. It is also fully supported in Node.js and Deno. For older environments, transpilation with Babel or a polyfill may be needed.