Unix Timestamp in JavaScript

JavaScript provides several built-in ways to get and work with Unix timestamps. Here's everything you need.

Get the current Unix timestamp

JavaScript

// Seconds (standard Unix timestamp)
Math.floor(Date.now() / 1000)       // e.g. 1700000000

// Milliseconds (used by most JS APIs)
Date.now()                           // e.g. 1700000000000

// Alternative ways
Math.floor(new Date() / 1000)
new Date().getTime()                 // milliseconds
+new Date()                          // milliseconds (unary +)

Convert epoch timestamp to Date

JavaScript

// If you have seconds, multiply by 1000 for JS Date
const epoch = 1700000000;
const date = new Date(epoch * 1000);

console.log(date.toISOString());     // "2023-11-14T22:13:20.000Z"
console.log(date.toUTCString());     // "Tue, 14 Nov 2023 22:13:20 GMT"
console.log(date.toLocaleString());  // local time string

Convert Date to epoch timestamp

JavaScript

// From a Date object
const date = new Date('2023-11-14T22:13:20Z');
const epochSeconds = Math.floor(date.getTime() / 1000);  // 1700000000
const epochMs = date.getTime();                           // 1700000000000

// From a date string
Math.floor(new Date('2026-01-01').getTime() / 1000)

// From specific components (UTC)
Math.floor(Date.UTC(2026, 0, 1, 0, 0, 0) / 1000)  // months are 0-indexed

Format epoch as readable date

JavaScript

const d = new Date(1700000000 * 1000);

// ISO 8601 (best for APIs and logs)
d.toISOString()                      // "2023-11-14T22:13:20.000Z"

// Locale-aware formatting
d.toLocaleString('en-US', { timeZone: 'America/New_York' })

// Custom format using Intl.DateTimeFormat
const fmt = new Intl.DateTimeFormat('en-GB', {
  year: 'numeric', month: '2-digit', day: '2-digit',
  hour: '2-digit', minute: '2-digit', second: '2-digit',
  timeZone: 'UTC', hour12: false
});
fmt.format(d);  // "14/11/2023, 22:13:20"

Add / subtract time from a timestamp

JavaScript

const now = Math.floor(Date.now() / 1000);

const oneHourLater   = now + 3600;
const oneDayLater    = now + 86400;
const oneWeekLater   = now + 604800;
const thirtyDaysAgo  = now - (30 * 86400);

Check if a timestamp is expired (e.g. JWT)

JavaScript

function isExpired(epochSeconds) {
  return Math.floor(Date.now() / 1000) > epochSeconds;
}

isExpired(1700000000);  // true — that date is in the past

Relative time ("5 minutes ago")

JavaScript

// Using Intl.RelativeTimeFormat (modern browsers)
function relativeTime(epochSeconds) {
  const diff = epochSeconds - Math.floor(Date.now() / 1000);
  const rtf = new Intl.RelativeTimeFormat('en', { numeric: 'auto' });
  const units = [
    ['year', 31536000], ['month', 2592000], ['week', 604800],
    ['day', 86400], ['hour', 3600], ['minute', 60], ['second', 1]
  ];
  for (const [unit, secs] of units) {
    if (Math.abs(diff) >= secs) {
      return rtf.format(Math.round(diff / secs), unit);
    }
  }
  return 'just now';
}

relativeTime(Date.now() / 1000 - 300);  // "5 minutes ago"

→ Use the live epoch converter to convert any JavaScript timestamp instantly.