Date

`Date.prototype.setHours`

Sets the hours for a specified date according to local time

Syntax

JavaScript

date.setHours(hoursValue, minutesValue?, secondsValue?, msValue?)

Parameters

Parameter	Type	Description
hoursValue	number	An integer from 0 to 23
minutesValue	number	Optional minutes (0-59)
secondsValue	number	Optional seconds (0-59)
msValue	number	Optional milliseconds (0-999)

Return Value

The number of milliseconds from epoch for the updated date

Examples

Basic Usage

const date = new Date();
date.setHours(0, 0, 0, 0);
console.log(date.getHours()); // 0 (midnight)

Practical Example

function startOfDay(date: Date) {
  const d = new Date(date);
  d.setHours(0, 0, 0, 0);
  return d;
}

Advanced Usage

function endOfDay(date: Date) {
  const d = new Date(date);
  d.setHours(23, 59, 59, 999);
  return d;
}

Understanding Date.prototype.setHours

The Date.prototype.setHours method in JavaScript sets the hours 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.setHours(hoursValue, minutesValue?, secondsValue?, msValue?). It accepts 4 parameters: hoursValue, minutesValue, secondsValue. When called, it returns the number of milliseconds from epoch for the updated date. Understanding when and how to use setHours() helps you write more expressive, readable code.

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

Browser support for Date.prototype.setHours 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.