JavaScript Unix Timestamp Guide

A comprehensive guide to working with Unix timestamps in JavaScript and Node.js. Learn how to get the current timestamp, convert between timestamps and Date objects, format dates, and handle timezones.

Quick Reference

Get Current Timestamp

Date.now()

Timestamp to Date

new Date(timestamp * 1000)

Date to Timestamp

Math.floor(date.getTime() / 1000)

Current Time (seconds)

Math.floor(Date.now() / 1000)

Getting the Current Unix Timestamp

JavaScript provides several ways to get the current Unix timestamp:

// Get current timestamp in milliseconds
const timestampMs = Date.now()
console.log(timestampMs)  // Output: 1733616000123

// Get current timestamp in seconds (Unix timestamp)
const timestamp = Math.floor(Date.now() / 1000)
console.log(timestamp)  // Output: 1733616000

// Alternative methods
const timestamp2 = Math.floor(new Date().getTime() / 1000)
const timestamp3 = Math.floor(+new Date() / 1000)

// All produce the same result
console.log(timestamp === timestamp2 === timestamp3)  // true

Note: JavaScript's Date.now() returns milliseconds. Divide by 1000 and use Math.floor() to get Unix timestamp in seconds.

Converting Timestamp to Date

Convert a Unix timestamp to a JavaScript Date object:

// Convert timestamp (seconds) to Date
const timestamp = 1733616000
const date = new Date(timestamp * 1000)  // Multiply by 1000!

console.log(date)  // Date object
console.log(date.toString())
// Output: Fri Dec 07 2024 18:00:00 GMT+0000

// Format the date
console.log(date.toISOString())
// Output: 2024-12-07T18:00:00.000Z

console.log(date.toLocaleDateString())
// Output: 12/7/2024 (depends on locale)

console.log(date.toLocaleString())
// Output: 12/7/2024, 6:00:00 PM

console.log(date.toUTCString())
// Output: Fri, 07 Dec 2024 18:00:00 GMT

// Convert millisecond timestamp
const timestampMs = 1733616000123
const date2 = new Date(timestampMs)  // No need to multiply

Important: Always multiply Unix timestamps (in seconds) by 1000 before passing to new Date() since it expects milliseconds!

Converting Date to Timestamp

Convert a Date object or date string to a Unix timestamp:

// Current date to timestamp
const now = new Date()
const timestamp = Math.floor(now.getTime() / 1000)
console.log(timestamp)  // Output: 1733616000

// Specific date to timestamp
const date = new Date('2024-12-07T18:00:00Z')
const timestamp2 = Math.floor(date.getTime() / 1000)
console.log(timestamp2)  // Output: 1733616000

// Using valueOf() (same as getTime())
const timestamp3 = Math.floor(date.valueOf() / 1000)

// Date string to timestamp
const dateString = '2024-12-07'
const timestamp4 = Math.floor(new Date(dateString).getTime() / 1000)

// Create specific date
const specificDate = new Date(2024, 11, 7, 18, 0, 0)  // Note: Month is 0-indexed!
const timestamp5 = Math.floor(specificDate.getTime() / 1000)

// Get millisecond timestamp (no division needed)
const timestampMs = now.getTime()
console.log(timestampMs)  // Output: 1733616000123

Formatting Dates

Format timestamps into readable date strings:

const timestamp = 1733616000
const date = new Date(timestamp * 1000)

// Built-in methods
console.log(date.toISOString())
// 2024-12-07T18:00:00.000Z

console.log(date.toLocaleDateString('en-US'))
// 12/7/2024

console.log(date.toLocaleTimeString('en-US'))
// 6:00:00 PM

console.log(date.toLocaleString('en-US'))
// 12/7/2024, 6:00:00 PM

// Using Intl.DateTimeFormat for more control
const formatter = new Intl.DateTimeFormat('en-US', {
  year: 'numeric',
  month: 'long',
  day: 'numeric',
  hour: '2-digit',
  minute: '2-digit',
  second: '2-digit',
  timeZoneName: 'short'
})

console.log(formatter.format(date))
// December 7, 2024 at 6:00:00 PM GMT

// Custom format function
function formatDate(date) {
  const year = date.getFullYear()
  const month = String(date.getMonth() + 1).padStart(2, '0')
  const day = String(date.getDate()).padStart(2, '0')
  const hours = String(date.getHours()).padStart(2, '0')
  const minutes = String(date.getMinutes()).padStart(2, '0')
  const seconds = String(date.getSeconds()).padStart(2, '0')

  return `${year}-${month}-${day} ${hours}:${minutes}:${seconds}`
}

console.log(formatDate(date))
// 2024-12-07 18:00:00

Working with Timezones

Handle different timezones using the Intl API:

const timestamp = 1733616000
const date = new Date(timestamp * 1000)

// Display in different timezones
const nyTime = new Intl.DateTimeFormat('en-US', {
  timeZone: 'America/New_York',
  dateStyle: 'full',
  timeStyle: 'long'
}).format(date)

console.log(nyTime)
// Friday, December 7, 2024 at 1:00:00 PM EST

const tokyoTime = new Intl.DateTimeFormat('en-US', {
  timeZone: 'Asia/Tokyo',
  dateStyle: 'full',
  timeStyle: 'long'
}).format(date)

console.log(tokyoTime)
// Saturday, December 8, 2024 at 3:00:00 AM JST

const londonTime = new Intl.DateTimeFormat('en-GB', {
  timeZone: 'Europe/London',
  dateStyle: 'full',
  timeStyle: 'long'
}).format(date)

console.log(londonTime)
// Friday, 7 December 2024 at 18:00:00 GMT

// Get timezone offset
const offset = date.getTimezoneOffset()
console.log(`Offset: ${offset} minutes`)

// Convert to UTC explicitly
const utcDate = new Date(date.toUTCString())
console.log(utcDate.toISOString())

Common Use Cases

Calculate Time Difference

// Calculate difference between two timestamps
const timestamp1 = 1733616000
const timestamp2 = 1733619600

const diffSeconds = timestamp2 - timestamp1
const diffMinutes = diffSeconds / 60
const diffHours = diffSeconds / 3600
const diffDays = diffSeconds / 86400

console.log(`Difference: ${diffSeconds} seconds`)
console.log(`Difference: ${diffHours} hours`)
console.log(`Difference: ${diffDays} days`)

// Human-readable difference
function getTimeDifference(timestamp1, timestamp2) {
  const diff = Math.abs(timestamp2 - timestamp1)
  const days = Math.floor(diff / 86400)
  const hours = Math.floor((diff % 86400) / 3600)
  const minutes = Math.floor((diff % 3600) / 60)
  const seconds = diff % 60

  return `${days}d ${hours}h ${minutes}m ${seconds}s`
}

console.log(getTimeDifference(timestamp1, timestamp2))
// Output: 0d 1h 0m 0s

Get Start of Day Timestamp

// Get timestamp for start of today (00:00:00)
const now = new Date()
const startOfDay = new Date(now.setHours(0, 0, 0, 0))
const timestamp = Math.floor(startOfDay.getTime() / 1000)

console.log(timestamp)

// Start of day in UTC
const startOfDayUTC = new Date(Date.UTC(
  now.getUTCFullYear(),
  now.getUTCMonth(),
  now.getUTCDate()
))
const timestampUTC = Math.floor(startOfDayUTC.getTime() / 1000)

console.log(timestampUTC)

Validate Timestamp

function isValidTimestamp(timestamp) {
  // Check if it's a number
  if (typeof timestamp !== 'number' || isNaN(timestamp)) {
    return false
  }

  // Check if timestamp is in reasonable range
  // Between Jan 1, 1970 and Jan 1, 2100
  const minTimestamp = 0
  const maxTimestamp = 4102444800  // Jan 1, 2100

  if (timestamp < minTimestamp || timestamp > maxTimestamp) {
    return false
  }

  // Try to create a valid date
  const date = new Date(timestamp * 1000)
  return !isNaN(date.getTime())
}

console.log(isValidTimestamp(1733616000))  // true
console.log(isValidTimestamp(-1000))       // false
console.log(isValidTimestamp(9999999999))  // false
console.log(isValidTimestamp('abc'))       // false

Best Practices

Use Date.now() for current timestamp

It's faster than new Date().getTime()

Always multiply Unix timestamps by 1000

JavaScript Date expects milliseconds, Unix timestamps are in seconds

Store timestamps in UTC

Convert to local timezone only for display

Use ISO 8601 format for APIs

Use toISOString() for consistent date exchange

Consider using libraries for complex operations

date-fns, dayjs, or Luxon provide better timezone and formatting support

Remember months are 0-indexed

January is 0, December is 11 in Date constructor

Related Tools & Resources

Timestamp Converter

Convert Unix timestamps to human-readable dates

Current Unix Time

View the current Unix timestamp in real-time

Python Guide

Learn Unix timestamps in Python

What is Unix Timestamp?

Learn the fundamentals of Unix time

Unix Timestamp & Time Tools