JavaScript - calculate time left to given date

In this article, we would like to show you how to calculate time left to given date in JavaScript.

Quick solution:

// ONLINE-RUNNER:browser;

const now = new Date().getTime();
const futureDate = new Date('27 Jan 2030 16:40:00').getTime();

const timeleft = futureDate - now;

const days    = Math.floor( timeleft / (1000 * 60 * 60 * 24));
const hours   = Math.floor((timeleft % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60));
const minutes = Math.floor((timeleft % (1000 * 60 * 60)) / (1000 * 60));
const seconds = Math.floor((timeleft % (1000 * 60)) / 1000);

console.log(days + ' days ' + hours + ' hours ' + minutes + ' minutes ' + seconds + ' seconds left');

Practical example

In this example, we calculate the difference between current date (now) and given date in three steps:

1. Get time that passed since Unix Epoch using Date() constructor with getTime(),
2. calculate the difference between current date and future date,
3. convert milliseconds to seconds, minutes, hours, etc.
4. calculate remaining time using modulo (%) operations and rounding the result using Math.floor() to get approximate result.

Runnable example:

// ONLINE-RUNNER:browser;

const now = new Date().getTime();
const futureDate = new Date('27 Jan 2030 16:40:00').getTime();

const timeleft = futureDate - now;

// convert milliseconds to seconds / minutes / hours etc.
const msPerSecond = 1000;
const msPerMinute = msPerSecond * 60;
const msPerHour = msPerMinute * 60;
const msPerDay = msPerHour * 24;

// calculate remaining time
const days = Math.floor(timeleft / msPerDay);
const hours = Math.floor((timeleft % (1000 * 60 * 60 * 24)) / msPerHour);
const minutes = Math.floor((timeleft % (1000 * 60 * 60)) / msPerMinute);
const seconds = Math.floor((timeleft % (1000 * 60)) / msPerSecond);

console.log(days + ' days ' + hours + ' hours ' + minutes + ' minutes ' + seconds + ' seconds left');

References

1. Math.floor() - JavaScript | MDN
2. Date() constructor - JavaScript | MDN
3. Date.prototype.getTime() - JavaScript | MDN