how to remove milliseconds from timestamp in js

Date Object in JavaScript

Handling dates in JavaScript often requires you to manipulate or format timestamps. In some cases, milliseconds are unnecessary, and removing them can simplify your date-handling tasks. This guide will show you several methods to remove milliseconds from a timestamp in JavaScript.

To remove milliseconds from a Date object, you can use toISOString() and slice(), set milliseconds to zero using setMilliseconds(0), or truncate the timestamp using Math.floor().

1. Using toISOString() and slice()

The toISOString() method returns a date string in ISO format, but it includes milliseconds. You can remove them by slicing off the last part of the string.

const date = new Date()
const noMilliseconds = date.toISOString().slice(0, -5) + 'Z' // Remove milliseconds
console.log(noMilliseconds) // Example: 2024-09-15T08:45:12Z

Explanation:

toISOString() returns a string like 2024-09-15T08:45:12.345Z. slice(0, -5) removes the .345Z part, leaving the timestamp without milliseconds.

2. Using setMilliseconds(0)

You can also directly modify a Date object to remove milliseconds by setting them to 0.

const date = new Date();
date.setMilliseconds(0); // Set milliseconds to 0
console.log(date.toISOString()); // Example: 2024-09-15T08:45:12.000Z

Explanation:

setMilliseconds(0) resets the milliseconds to zero, which then reflects in the output when you format the date.

3. Using Math.floor() and getTime()

If you’re working with timestamps (which represent milliseconds), you can remove the milliseconds by truncating them.

const timestamp = Date.now(); // Get current timestamp in milliseconds
const noMilliseconds = Math.floor(timestamp / 1000) * 1000; // Remove milliseconds
console.log(new Date(noMilliseconds)); // Convert back to Date object

Explanation:

Date.now() returns the current timestamp in milliseconds. By dividing by 1000, you convert the timestamp to seconds, and Math.floor() removes any fractional milliseconds.

4. Using Custom Libraries Like Day.js

Libraries like Day.js and Moment.js can simplify date formatting tasks. Here’s an example using Day.js to remove milliseconds:

const dayjs = require('dayjs');
console.log(dayjs().format('YYYY-MM-DDTHH:mm:ssZ')); // No milliseconds
    

When to Remove Milliseconds Removing milliseconds is useful in cases where:

Logging: Precision down to seconds is often sufficient for logging events. Comparisons: If comparing dates without worrying about milliseconds, removing them simplifies the logic. Data storage: Omitting milliseconds reduces the complexity of timestamp data.